Biology Quiz: Toughest MCQ! Exam
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- 1.
Macrophages circulate in the blood and are attracted by signals from infected tissue and then destroy the pathogen.
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
Macrophages are immune cells that play a crucial role in the body's defense against pathogens. They are able to move freely throughout the bloodstream and are attracted to signals released by infected tissues. Once they reach the infected area, they engulf and destroy the pathogens through a process called phagocytosis. Therefore, the statement that macrophages circulate in the blood and are attracted by signals from infected tissue to destroy the pathogen is true.Rate this question:
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- 2.
The immunity which is specialized for a specific class of pathogen is considered:
- A.
Adaptive
- B.
Innate
- C.
Both
Correct Answer
B. InnateExplanation
The correct answer is "innate" because innate immunity refers to the body's natural defense mechanisms that are present from birth and provide a general defense against a wide range of pathogens, regardless of their specific class. It includes physical barriers like skin and mucous membranes, as well as cellular and chemical components such as phagocytes and antimicrobial proteins. Adaptive immunity, on the other hand, is a specific immune response that develops over time in response to exposure to a particular pathogen or antigen.Rate this question:
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- 3.
What does each character refer to (A,B,C)?
- A.
Argon complex protein, dicer 2 ,single stranded RNA
- B.
Dicer 2, argon complex protein ,single stranded mRNA
- C.
Lysozyme , argon complex proteins , dicer 2
- D.
Dicer 2 , argon complex proteins,double stranded mRNA
Correct Answer
B. Dicer 2, argon complex protein ,single stranded mRNAExplanation
The correct answer is Dicer 2, argon complex protein, single stranded mRNA. This is because Dicer 2 is an enzyme involved in the RNA interference pathway, where it cleaves double stranded RNA into small interfering RNAs (siRNAs). The argon complex protein is a component of the RNA-induced silencing complex (RISC), which is responsible for binding to the siRNAs and guiding them to their target mRNA molecules. Therefore, Dicer 2 and the argon complex protein are both involved in the processing and regulation of RNA molecules. The reference to single stranded mRNA indicates that this is the type of RNA molecule being targeted and regulated by these proteins.Rate this question:
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- 4.
The type of the cell and the name of the regions (x) is :
- A.
Dendritic cell , variable region
- B.
B cell , variable region
- C.
T cell , variable region
- D.
T cell , constant region
Correct Answer
B. B cell , variable regionExplanation
The correct answer is B cell, variable region. B cells are a type of white blood cell that are responsible for producing antibodies. The variable region of a B cell refers to the part of the antibody molecule that is responsible for binding to specific antigens. This region is highly variable, allowing B cells to recognize and bind to a wide range of different antigens.Rate this question:
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- 5.
The process X and the organelle B are (respectively):
- A.
Exocytosis ,lysosome
- B.
Endocytosis ,vacuole
- C.
Endocytosis , lysosome
- D.
Exocytosis , pathogen
Correct Answer
C. Endocytosis , lysosomeExplanation
The process X mentioned in the question refers to endocytosis, which is the process by which cells take in substances from the external environment. The organelle B mentioned in the question is lysosome, which is responsible for breaking down cellular waste and foreign material. Endocytosis involves the formation of a vesicle that contains the substance being taken in, and this vesicle then fuses with a lysosome to break down the contents. Therefore, the correct answer is endocytosis, lysosome.Rate this question:
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- 6.
A set of events triggered by signaling molecules released upon injury or infection is
- A.
Apoptosis
- B.
Inflammatory response
- C.
Humoral immunity
- D.
None of the above
Correct Answer
B. Inflammatory responseExplanation
The correct answer is the inflammatory response. When the body is injured or infected, signaling molecules are released to initiate a series of events known as the inflammatory response. This response is characterized by increased blood flow, accumulation of immune cells, and release of inflammatory mediators to eliminate the pathogen or repair the damaged tissue. Apoptosis refers to programmed cell death, while humoral immunity is a specific immune response mediated by antibodies.Rate this question:
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- 7.
Activation of B cells needs :
- A.
Helper T cells
- B.
Pathogen (proteins in the surface of the pathogen )
- C.
A+B
- D.
Inflammatory response
Correct Answer
C. A+BExplanation
The activation of B cells requires both Helper T cells and the presence of pathogen proteins on the surface of the pathogen. Helper T cells play a crucial role in activating B cells by releasing cytokines and providing necessary signals. Pathogen proteins, also known as antigens, bind to B cell receptors, triggering their activation. Therefore, the correct answer is A+B, indicating that both Helper T cells and pathogen proteins are required for B cell activation.Rate this question:
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- 8.
For the successful development of a vaccine to be used against a pathogen, it is necessary that :
- A.
The surface antigens of the pathogen stay the same
- B.
All of the surface antigens of the pathogen be identified
- C.
The pathogen has only one epitope
- D.
The major histocompatibilty MHC molecules are hetrozygous
Correct Answer
A. The surface antigens of the pathogen stay the sameExplanation
For the successful development of a vaccine, it is necessary that the surface antigens of the pathogen stay the same. This is because vaccines work by stimulating the immune system to recognize and target specific antigens on the surface of the pathogen. If the surface antigens of the pathogen change, the vaccine may no longer be effective in providing immunity against the pathogen. Therefore, having stable surface antigens is crucial for the long-term effectiveness of a vaccine.Rate this question:
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- 9.
Which of the following is an example of alternation of generations?
- A.
A grandparent and grandchild each have dark hair, but the parent has blond hair.
- B.
A diploid plant (sporophyte) produces, by meiosis, a spore that gives rise to a multicellular, haploid pollen grain (gametophyte).
- C.
A diploid animal produces gametes by meiosis, and the gametes undergo fertilization to produce a diploid zygote.
- D.
A haploid mushroom produces gametes by mitosis, and the gametes undergo fertilization, which is immediately followed by meiosis.
- E.
A diploid cell divides by mitosis to produce two diploid daughter cells, which then fuse to produce a tetraploid cell.
Correct Answer
B. A diploid plant (sporophyte) produces, by meiosis, a spore that gives rise to a multicellular, haploid pollen grain (gametophyte).Explanation
Alternation of generations refers to a life cycle where an organism alternates between two different multicellular forms, one haploid (gametophyte) and one diploid (sporophyte). In this example, the diploid plant (sporophyte) produces a spore through meiosis, which then develops into a multicellular, haploid pollen grain (gametophyte). This demonstrates the alternating generations of haploid and diploid forms in the life cycle of the plant.Rate this question:
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- 10.
The karyotype of one species of primate has 48 chromosomes. In a particular female, cell division goes awry and she produces one of her eggs with an extra chromosome (25). The most probable source of this error would be a mistake in which of the following?
- A.
Mitosis in her ovary
- B.
Metaphase I of one meiotic event
- C.
Telophase II of one meiotic event
- D.
Telophase I of one meiotic event
- E.
Either anaphase I or II
Correct Answer
E. Either anaphase I or IIExplanation
In this scenario, the female primate produces an egg with an extra chromosome (25). This indicates a mistake in the process of meiosis, specifically in either anaphase I or anaphase II. Anaphase is the stage of cell division where chromosomes are separated and pulled towards opposite ends of the cell. If an error occurs during anaphase I or anaphase II, it can result in an unequal distribution of chromosomes, leading to the production of an egg with an extra chromosome.Rate this question:
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- 11.
A given organism has 46 chromosomes in its karyotype. We can therefore conclude which of the following?
- A.
It must be human.
- B.
It must be a primate.
- C.
It must be an animal.
- D.
It must be sexually reproducing.
- E.
Its gametes must have 23 chromosomes.
Correct Answer
E. Its gametes must have 23 chromosomes.Explanation
The statement "Its gametes must have 23 chromosomes" can be concluded from the fact that the organism has 46 chromosomes in its karyotype. In sexually reproducing organisms, gametes are produced through a process called meiosis, which involves the halving of the chromosome number. Therefore, if the organism has 46 chromosomes, its gametes must have half that number, which is 23 chromosomes. This conclusion is not specific to humans, primates, or animals in general, as the chromosome number can vary among different species.Rate this question:
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- 12.
A triploid cell contains three sets of chromosomes. If a cell of a usually diploid species with 42 chromosomes per cell is triploid, this cell would be expected to have which of the following?
- A.
63 chromosomes in 31 1/2 pairs
- B.
63 chromosomes in 21 sets of 3
- C.
63 chromosomes, each with three chromatids
- D.
21 chromosome pairs and 21 unique chromosomes
Correct Answer
B. 63 chromosomes in 21 sets of 3Explanation
A triploid cell contains three sets of chromosomes, so if a diploid cell with 42 chromosomes per cell becomes triploid, it would have three times the number of chromosomes, which is 126. Since each set of chromosomes in the triploid cell contains three chromosomes, there would be 21 sets of 3 chromosomes in total. Therefore, the correct answer is "63 chromosomes in 21 sets of 3".Rate this question:
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- 13.
A karyotype results from which of the following?
- A.
A natural cellular arrangement of chromosomes in the nucleus
- B.
An inherited ability of chromosomes to arrange themselves
- C.
The ordering of human chromosome images
- D.
The cutting and pasting of parts of chromosomes to form the standard array E) the separation of homologous chromosomes at metaphase I of meiosis
Correct Answer
C. The ordering of human chromosome imagesExplanation
A karyotype results from the ordering of human chromosome images. This involves arranging the chromosomes in a specific order based on their size, shape, and other characteristics. By examining the karyotype, geneticists can identify any abnormalities or variations in the number or structure of chromosomes, which can help in diagnosing genetic disorders or conditions.Rate this question:
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- 14.
Which of the following best describes a karyotype?
- A.
A pictorial representation of all the genes for a species
- B.
A display of each of the chromosomes of a single cell
- C.
The combination of all the maternal and paternal chromosomes of a species
- D.
The collection of all the chromosomes in an individual organism
- E.
A photograph of all the cells with missing or extra chromosomes
Correct Answer
B. A display of each of the chromosomes of a single cellExplanation
A karyotype is a display of each of the chromosomes of a single cell. It shows the number, size, and shape of the chromosomes, and can be used to identify any abnormalities or genetic disorders. It provides a visual representation of an individual's genetic makeup and is often used in medical and genetic research.Rate this question:
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- 15.
If a cell has completed the first meiotic division and is just beginning meiosis II, which of the following is an appropriate description of its contents?
- A.
It has half the amount of DNA as the cell that began meiosis
- B.
It has the same number of chromosomes but each of them has different alleles than another cell from the same meiosis.
- C.
It has half the chromosomes but twice the DNA of the originating cell.
- D.
It has one-fourth the DNA and one-half the chromosomes as the originating cell. E) It is identical in content to another cell from the same meiosis.
Correct Answer
A. It has half the amount of DNA as the cell that began meiosisExplanation
During meiosis I, the cell undergoes DNA replication, resulting in two sister chromatids held together by a centromere. When meiosis I is completed and the cell enters meiosis II, the sister chromatids separate, resulting in two daughter cells. Each daughter cell will have half the amount of DNA as the original cell because the DNA has already replicated during meiosis I. Therefore, the correct answer is that the cell has half the amount of DNA as the cell that began meiosis.Rate this question:
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- 16.
How do cells at the completion of meiosis compare with cells that have replicated their DNA and are just about to begin meiosis?
- A.
They have twice the amount of cytoplasm and half the amount of DNA.
- B.
They have half the number of chromosomes and half the amount of DNA.
- C.
They have the same number of chromosomes and half the amount of DNA.
- D.
They have half the number of chromosomes and one-fourth the amount of DNA
- E.
They have half the amount of cytoplasm and twice the amount of DNA.
Correct Answer
D. They have half the number of chromosomes and one-fourth the amount of DNAExplanation
Cells at the completion of meiosis have undergone two rounds of cell division, resulting in the formation of four haploid cells. These cells have half the number of chromosomes compared to cells that have replicated their DNA and are about to begin meiosis. Additionally, during meiosis, DNA is divided equally among the four resulting cells, meaning each cell has only one-fourth of the amount of DNA compared to cells that are about to begin meiosis.Rate this question:
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- 17.
When does the synaptonemal complex disappear?
- A.
Late prophase of meiosis I
- B.
During fertilization or fusion of gametes
- C.
Early anaphase of meiosis I
- D.
Mid-prophase of meiosis II
- E.
Late metaphase of meiosis II
Correct Answer
A. Late prophase of meiosis IExplanation
The synaptonemal complex disappears during late prophase of meiosis I. In meiosis, the synaptonemal complex is a protein structure that forms between homologous chromosomes during prophase I. It helps to align the chromosomes and facilitate genetic recombination. However, as meiosis progresses, the synaptonemal complex disassembles, allowing the homologous chromosomes to separate and proceed to metaphase I. Therefore, the correct answer is late prophase of meiosis I.Rate this question:
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- 18.
Which of the following happens at the conclusion of meiosis I?
- A.
Homologous chromosomes are separated.
- B.
The chromosome number per cell is conserved.
- C.
Sister chromatids are separated
- D.
Four daughter cells are formed
- E.
The sperm cells elongate to form a head and a tail end
Correct Answer
A. Homologous chromosomes are separated.Explanation
At the conclusion of meiosis I, homologous chromosomes are separated. This is because during meiosis I, the homologous chromosomes pair up and exchange genetic material through a process called crossing over. Then, the homologous chromosomes are pulled apart and move to opposite poles of the cell. This separation ensures that each daughter cell receives one copy of each homologous chromosome, resulting in genetic diversity and the formation of haploid cells. The other options are incorrect because the chromosome number is reduced by half, sister chromatids are still held together, four daughter cells are formed at the end of meiosis II, and the elongation of sperm cells occurs during spermiogenesis, not meiosis I.Rate this question:
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- 19.
A cell divides to produce two daughter cells that are genetically different.
- A.
The statement is true for mitosis only.
- B.
The statement is true for meiosis I only.
- C.
The statement is true for meiosis II only.
- D.
The statement is true for mitosis and meiosis I
- E.
The statement is true for mitosis and meiosis II.
Correct Answer
B. The statement is true for meiosis I only. -
- 20.
Chromatids are separated from each other.
- A.
The statement is true for mitosis only.
- B.
The statement is true for meiosis I only.
- C.
The statement is true for meiosis II only.
- D.
The statement is true for mitosis and meiosis I.
- E.
The statement is true for mitosis and meiosis II.
Correct Answer
E. The statement is true for mitosis and meiosis II.Explanation
During mitosis, chromatids are separated from each other to form two identical daughter cells. Similarly, during meiosis II, the sister chromatids are also separated to form four haploid daughter cells. Therefore, the correct answer is that the statement is true for both mitosis and meiosis II.Rate this question:
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- 21.
Cystic fibrosis affects the lungs, the pancreas, the digestive system, and other organs, resulting in symptoms ranging from breathing difficulties to recurrent infections. Which of the following terms best describes this?
- A.
Incomplete dominance
- B.
Multiple alleles
- C.
Pleiotropy
- D.
Epistasis
- E.
Codominance
Correct Answer
C. PleiotropyExplanation
Pleiotropy is the best term to describe the symptoms of cystic fibrosis because it refers to a single gene having multiple effects on different organs or systems in the body. In the case of cystic fibrosis, the gene mutation affects various organs such as the lungs, pancreas, and digestive system, leading to a range of symptoms including breathing difficulties and recurrent infections. This demonstrates the concept of pleiotropy, where a mutation in one gene can have multiple effects throughout the body.Rate this question:
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- 22.
Which of the following is an example of polygenic inheritance?
- A.
Pink flowers in snapdragons
- B.
The ABO blood group in humans
- C.
Huntington's disease in humans
- D.
White and purple flower color in peas
- E.
Skin pigmentation in humans
Correct Answer
E. Skin pigmentation in humansExplanation
Skin pigmentation in humans is an example of polygenic inheritance because it is controlled by multiple genes. The variation in skin color is not determined by a single gene, but rather by the combined effects of several genes. This is why there is a wide range of skin tones observed in human populations.Rate this question:
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- 23.
Hydrangea plants of the same genotype are planted in a large flower garden. Some of the plants produce blue flowers and others pink flowers. This can be best explained by which of the following?
- A.
The knowledge that multiple alleles are involved
- B.
The allele for blue hydrangea being completely dominant
- C.
The alleles being codominant
- D.
The fact that a mutation has occurred
- E.
Environmental factors such as soil pH
Correct Answer
E. Environmental factors such as soil pHExplanation
The color of hydrangea flowers is influenced by the soil pH. The availability of aluminum ions in acidic soil promotes the production of blue flowers, while alkaline soil inhibits the uptake of aluminum ions, resulting in pink flowers. Therefore, the variation in flower color among hydrangea plants of the same genotype can be best explained by the influence of environmental factors, specifically the soil pH.Rate this question:
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- 24.
Which of the following provides an example of epistasis?
- A.
Recessive genotypes for each of two genes (aabb) results in an albino corn snake.
- B.
The allele b17 produces a dominant phenotype, although b1 through b16 do not.
- C.
In rabbits and many other mammals, one genotype (cc) prevents any fur color from developing.
- D.
In Drosophila (fruit flies), white eyes can be due to an X-linked gene or to a combination of other genes.
- E.
In cacti, there are several genes for the type of spines.
Correct Answer
C. In rabbits and many other mammals, one genotype (cc) prevents any fur color from developing.Explanation
In rabbits and many other mammals, the genotype cc prevents any fur color from developing. This is an example of epistasis because the presence of the cc genotype overrides the effects of other genes that control fur color. In other words, the presence of the cc genotype masks the expression of other genes related to fur color, resulting in the absence of fur color regardless of the presence of other color-determining genes.Rate this question:
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- 25.
An obstetrician knows that one of her patients is a pregnant woman whose fetus is at risk for a serious disorder that is detectable biochemically in fetal cells. The obstetrician would most reasonably offer which of the following procedures to her patient?
- A.
CVS
- B.
Ultrasound imaging
- C.
Amniocentesis
- D.
Blood transfusion
- E.
X-ray
Correct Answer
C. AmniocentesisExplanation
Amniocentesis is a procedure that involves the removal of a small amount of amniotic fluid from the uterus to analyze the fetal cells for any genetic disorders or abnormalities. In this scenario, the obstetrician knows that the patient's fetus is at risk for a serious disorder that can be detected biochemically in fetal cells. Amniocentesis would be the most reasonable procedure to offer as it allows for the analysis of the fetal cells and can provide valuable information about the health of the fetus.Rate this question:
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- 26.
The frequency of heterozygosity for the sickle-cell anemia allele is unusually high, presumably because this reduces the frequency of malaria. Such a relationship is related to which of the following?
- A.
Mendel's law of independent assortment
- B.
Mendel's law of segregation
- C.
Darwin's explanation of natural selection
- D.
Darwin's observations of competition
- E.
The malarial parasite changing the allele
Correct Answer
C. Darwin's explanation of natural selectionExplanation
The explanation for the correct answer is that Darwin's explanation of natural selection is related to the relationship between the frequency of heterozygosity for the sickle-cell anemia allele and the reduction in the frequency of malaria. Darwin's explanation of natural selection states that individuals with advantageous traits are more likely to survive and reproduce, leading to an increase in the frequency of those traits in a population over time. In this case, individuals with the sickle-cell anemia allele have an advantage in regions with a high prevalence of malaria, as it provides some resistance to the disease. Therefore, natural selection favors the heterozygous individuals, leading to a higher frequency of heterozygosity for the sickle-cell anemia allele in those regions.Rate this question:
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- 27.
Phenylketonuria (PKU) is a recessive human disorder in which an individual cannot appropriately metabolize a particular amino acid. The amino acid is not otherwise produced by humans. Therefore, the most efficient and effective treatment is which of the following?
- A.
Feed them the substrate that can be metabolized into this amino acid.
- B.
Transfuse the patients with blood from unaffected donors
- C.
Regulate the diet of the affected persons to severely limit the uptake of the amino acid.
- D.
Feed the patients the missing enzymes in a regular cycle, such as twice per week.
- E.
Feed the patients an excess of the missing product.
Correct Answer
C. Regulate the diet of the affected persons to severely limit the uptake of the amino acid.Explanation
The most efficient and effective treatment for Phenylketonuria (PKU) is to regulate the diet of the affected persons to severely limit the uptake of the amino acid. Since the individual cannot appropriately metabolize the amino acid, it is necessary to reduce its intake to prevent its accumulation and related health issues. This can be achieved by carefully controlling the diet and avoiding foods that contain high levels of the amino acid. By doing so, the symptoms and complications of PKU can be minimized, promoting better health and quality of life for the affected individuals.Rate this question:
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- 28.
Hutchinson-Gilford progeria is an exceedingly rare human genetic disorder in which there is very early senility and death, usually from coronary artery disease, at an average age of approximately 13. Patients, who look very old even as children, do not live to reproduce. Which of the following represents the most likely assumption?
- A.
All cases must occur in relatives; therefore, there must be only one mutant allele
- B.
Successive generations of a family will continue to have more and more cases over time.
- C.
The disorder may be due to mutation in a single protein-coding gene.
- D.
The disease is autosomal dominant.
- E.
Each patient will have had at least one affected family member in a previous generation
Correct Answer
C. The disorder may be due to mutation in a single protein-coding gene.Explanation
The most likely assumption is that the disorder may be due to a mutation in a single protein-coding gene. This is because Hutchinson-Gilford progeria is a genetic disorder, and it is often caused by mutations in the LMNA gene, which codes for a protein called lamin A. These mutations lead to the production of an abnormal form of lamin A, which affects the structure and function of the nucleus in cells. Therefore, it is reasonable to assume that a mutation in a single gene could be responsible for this disorder.Rate this question:
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- 29.
Most genes have many more than two alleles. However, which of the following is also true?
- A.
At least one allele for a gene always produces a dominant phenotype.
- B.
Most of the alleles will never be found in a live-born organism.
- C.
All of the alleles but one will produce harmful effects if homozygous.
- D.
There may still be only two phenotypes for the trait.
- E.
More than two alleles in a genotype is considered lethal.
Correct Answer
D. There may still be only two phenotypes for the trait.Explanation
The statement "There may still be only two phenotypes for the trait" is true because even though there can be many alleles for a gene, only two of them may determine the observable characteristics or phenotypes. This is because some alleles may be recessive and not expressed in the presence of a dominant allele. Therefore, despite the presence of multiple alleles, the phenotypes may still be limited to two options.Rate this question:
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- 30.
How could you best predict the maximum number of alleles for a single gene whose polypeptide product is known?
- A.
Search the population for all phenotypic variants of this polypeptide.
- B.
Count the number of amino acids in the polypeptide.
- C.
Mate all known genotypes and collect all possible offspring different from the parents.
- D.
Measure the rate of new mutations in the species and estimate the number since it first evolved
- E.
Count the number of DNA nucleotides that are in the code for the polypeptides.
Correct Answer
E. Count the number of DNA nucleotides that are in the code for the polypeptides.Explanation
To predict the maximum number of alleles for a single gene whose polypeptide product is known, counting the number of DNA nucleotides that are in the code for the polypeptides would be the most effective approach. This is because the number of nucleotides in the DNA sequence directly determines the number of possible combinations and variations that can occur in the gene. By counting the nucleotides, we can assess the potential for different alleles and genetic variations within the population. The other options mentioned, such as searching for phenotypic variants or measuring mutation rates, may provide valuable information but may not directly correlate with the maximum number of alleles.Rate this question:
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- 31.
An ideal procedure for fetal testing in humans would have which of the following features?
- A.
The procedure that can be performed at the earliest time in the pregnancy
- B.
Lowest risk procedure that would provide the most reliable information
- C.
The procedure that can test for the greatest number of traits at once
- D.
A procedure that provides a three-dimensional image of the fetus
- E.
A procedure that could test for the carrier status of the fetus
Correct Answer
A. The procedure that can be performed at the earliest time in the pregnancyExplanation
The ideal procedure for fetal testing in humans would be the one that can be performed at the earliest time in the pregnancy. This is because early testing allows for early detection of any potential abnormalities or genetic disorders in the fetus, which can then lead to timely interventions or decisions regarding the pregnancy. Early testing also provides more time for parents to prepare emotionally and make informed choices about the future of the pregnancy.Rate this question:
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- 32.
A scientist discovers a DNA-based test for one allele of a particular gene. This and only this allele, if homozygous, produces an effect that results in death at or about the time of birth. Of the following, which is the best use of this discovery?
- A.
Screen all newborns of an at-risk population
- B.
Design a test for identifying heterozygous carriers of the allele.
- C.
Introduce a normal allele into deficient newborns
- D.
Follow the segregation of the allele during meiosis.
- E.
Test school-age children for the disorder.
Correct Answer
B. Design a test for identifying heterozygous carriers of the allele.Explanation
The best use of the DNA-based test for one allele of a particular gene that causes death at or about the time of birth is to design a test for identifying heterozygous carriers of the allele. This is because individuals who are heterozygous carriers have one copy of the allele and one normal allele, which means they do not exhibit the lethal effect of the homozygous allele. Identifying carriers is important for genetic counseling and family planning, as it allows individuals to make informed decisions about having children and potentially avoiding the birth of affected individuals.Rate this question:
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- 33.
In his transformation experiments, what did Griffith observe?
- A.
Mutant mice were resistant to bacterial infections
- B.
Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form.
- C.
Mixing a heat-killed nonpathogenic strain of bacteria with a living pathogenic strain makes the pathogenic strain nonpathogenic.
- D.
Infecting mice with nonpathogenic strains of bacteria makes them resistant to pathogenic strains.
- E.
Mice infected with a pathogenic strain of bacteria can spread the infection to other mice.
Correct Answer
B. Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form.Explanation
Griffith observed that mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form. This suggests that there is a transfer of genetic material between the two strains, leading to the transformation of nonpathogenic cells into pathogenic cells. This experiment provided evidence for the concept of bacterial transformation, which later played a crucial role in understanding the process of genetic transfer and the discovery of DNA as the genetic material.Rate this question:
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- 34.
How do we describe transformation in bacteria?
- A.
The creation of a strand of DNA from an RNA molecule
- B.
The creation of a strand of RNA from a DNA molecule
- C.
The infection of cells by a phage DNA molecule
- D.
The type of semiconservative replication shown by DNA
- E.
Assimilation of external DNA into a cell
Correct Answer
E. Assimilation of external DNA into a cellExplanation
Transformation in bacteria refers to the process of assimilating external DNA into a bacterial cell. This involves the uptake and incorporation of foreign DNA into the bacterial genome, allowing the bacterium to acquire new genetic traits. This process is important for genetic diversity and adaptation in bacteria.Rate this question:
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- 35.
After mixing a heat-killed, phosphorescent strain of bacteria with a living nonphosphorescent strain, you discover that some of the living cells are now phosphorescent. Which observations would provide the best evidence that the ability to fluoresce is a heritable trait?
- A.
DNA passed from the heat-killed strain to the living strain.
- B.
Protein passed from the heat-killed strain to the living strain
- C.
The phosphorescence in the living strain is especially bright.
- D.
Descendants of the living cells are also phosphorescent.
- E.
Both DNA and protein passed from the heat-killed strain to the living strain.
Correct Answer
D. Descendants of the living cells are also phosphorescent.Explanation
The observation that descendants of the living cells are also phosphorescent provides the best evidence that the ability to fluoresce is a heritable trait. This suggests that the genetic material responsible for phosphorescence is being passed on from one generation to the next, indicating that the trait is inherited and not a result of temporary protein or DNA transfer.Rate this question:
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- 36.
In trying to determine whether DNA or protein is the genetic material, Hershey and Chase made use of which of the following facts?
- A.
DNA contains sulfur, whereas protein does not.
- B.
DNA contains phosphorus, whereas protein does not.
- C.
DNA contains nitrogen, whereas protein does not.
- D.
DNA contains purines, whereas protein includes pyrimidines
- E.
RNA includes ribose, whereas DNA includes deoxyribose sugars.
Correct Answer
B. DNA contains phosphorus, whereas protein does not.Explanation
Hershey and Chase made use of the fact that DNA contains phosphorus, whereas protein does not. This was a crucial observation because they were investigating whether DNA or protein is the genetic material. By labeling the DNA with radioactive phosphorus and the protein with radioactive sulfur, they were able to track which molecule was being passed on to the next generation of bacteriophages. The fact that the radioactive phosphorus was found in the progeny bacteriophages confirmed that DNA is indeed the genetic material.Rate this question:
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- 37.
Which of the following investigators was/were responsible for the following discovery? In DNA from any species, the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine.
- A.
Frederick Griffith
- B.
Alfred Hershey and Martha Chase
- C.
Oswald Avery, Maclyn McCarty, and Colin MacLeod
- D.
Erwin Chargaff
- E.
Matthew Meselson and Franklin Stahl
Correct Answer
D. Erwin ChargaffExplanation
Erwin Chargaff was responsible for the discovery that in DNA from any species, the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine.Rate this question:
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- 38.
Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?
- A.
8%
- B.
16%
- C.
31%
- D.
42%
- E.
It cannot be determined from the information provided.
Correct Answer
A. 8%Explanation
Based on the information provided, we know that cytosine makes up 42% of the nucleotides in the DNA sample. In DNA, cytosine always pairs with guanine, and thymine always pairs with adenine. Therefore, the percentage of thymine should be equal to the percentage of adenine. Since the information about the percentage of adenine is not given, we cannot determine the exact percentage of thymine. Hence, the answer is "It cannot be determined from the information provided."Rate this question:
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- 39.
Which of the following can be determined directly from X-ray diffraction photographs of crystallized DNA?
- A.
The diameter of the helix
- B.
The rate of replication
- C.
The sequence of nucleotides
- D.
The bond angles of the subunits
- E.
The frequency of A vs. T nucleotides
Correct Answer
A. The diameter of the helixExplanation
X-ray diffraction photographs of crystallized DNA can provide information about the structure of the DNA molecule. By analyzing the diffraction pattern, scientists can determine the diameter of the helix, which refers to the width of the DNA double helix. This can be calculated by measuring the distance between the diffraction spots. The other options listed, such as the rate of replication, sequence of nucleotides, bond angles of the subunits, and frequency of A vs. T nucleotides, cannot be directly determined from X-ray diffraction photographs.Rate this question:
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- 40.
It became apparent to Watson and Crick after completion of their model that the DNA molecule could carry a vast amount of hereditary information in which of the following?
- A.
Sequence of bases
- B.
Phosphate-sugar backbones
- C.
Complementary pairing of bases
- D.
Side groups of nitrogenous bases
- E.
Different five-carbon sugars
Correct Answer
A. Sequence of basesExplanation
The correct answer is the sequence of bases. Watson and Crick realized that the arrangement of the four nitrogenous bases (adenine, thymine, cytosine, and guanine) along the DNA molecule could encode and carry genetic information. The specific order of these bases forms the genetic code that determines the instructions for building and functioning of organisms. This discovery was crucial in understanding the structure and function of DNA and paved the way for advancements in genetics and molecular biology.Rate this question:
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- 41.
In an analysis of the nucleotide composition of DNA, which of the following will be found?
- A.
A = C
- B.
A = G and C = T
- C.
A + C = G + T
- D.
G + C = T + A
Correct Answer
C. A + C = G + TExplanation
In DNA, the amount of adenine (A) is always equal to the amount of cytosine (C), and the amount of guanine (G) is always equal to the amount of thymine (T). This is known as Chargaff's rule. Therefore, the correct answer is A + C = G + T, as the total amount of adenine and cytosine will always be equal to the total amount of guanine and thymine in DNA.Rate this question:
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- 42.
Replication in prokaryotes differs from replication in eukaryotes for which of the following reasons?
- A.
Prokaryotic chromosomes have histones, whereas eukaryotic chromosomes do not.
- B.
Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many.
- C.
The rate of elongation during DNA replication is slower in prokaryotes than in eukaryotes
- D.
Prokaryotes produce Okazaki fragments during DNA replication, but eukaryotes do not.
- E.
Prokaryotes have telomeres, and eukaryotes do not
Correct Answer
B. Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many.Explanation
In prokaryotes, replication occurs from a single origin of replication, meaning that the entire chromosome is replicated simultaneously. On the other hand, eukaryotes have multiple origins of replication spread throughout their chromosomes, resulting in multiple replication forks and the replication of different sections of the chromosome at the same time. This difference in the number of replication origins is a key distinction between replication in prokaryotes and eukaryotes.Rate this question:
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- 43.
What is meant by the description "antiparallel" regarding the strands that make up DNA?
- A.
The twisting nature of DNA creates nonparallel strands.
- B.
The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand.
- C.
Base pairings create unequal spacing between the two DNA strands.
- D.
One strand is positively charged and the other is negatively charged.
- E.
One strand contains only purines and the other contains only pyrimidines.
Correct Answer
B. The 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand.Explanation
The term "antiparallel" refers to the opposite orientation or direction of the two strands that make up DNA. In DNA, one strand runs in the 5' to 3' direction, while the other runs in the opposite direction, 3' to 5'. This antiparallel arrangement is important for the complementary base pairing between the strands, where adenine pairs with thymine and guanine pairs with cytosine. This arrangement allows for the formation of the double helix structure of DNA and is essential for DNA replication and protein synthesis.Rate this question:
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- 44.
In a well-fed human eating a Western diet, the richest source of stored chemical energy in the body is
- A.
Fat in adipose tissue.
- B.
Glucose in the blood.
- C.
Protein in muscle cells.
- D.
Glycogen in muscle cells.
- E.
Calcium phosphate in bone.
Correct Answer
A. Fat in adipose tissue.Explanation
In a well-fed human eating a Western diet, the richest source of stored chemical energy in the body is fat in adipose tissue. Adipose tissue is responsible for storing excess energy in the form of triglycerides, which are made up of fatty acids. These fatty acids can be broken down and used as a source of energy when the body needs it. Glucose in the blood and glycogen in muscle cells are also sources of energy, but they are not as richly stored as fat in adipose tissue. Protein in muscle cells is primarily used for muscle contraction and repair, not as a source of stored energy. Calcium phosphate in bone is not a source of stored chemical energy.Rate this question:
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- 45.
Animals that migrate great distances would obtain the greatest energetic benefit of storing chemical energy as
- A.
Proteins.
- B.
Minerals.
- C.
Carbohydrates.
- D.
Amino acids.
- E.
Fats
Correct Answer
E. FatsExplanation
Animals that migrate great distances require a high amount of energy to sustain their long journeys. Fats are the most efficient form of storing chemical energy as they provide more than twice the energy per unit compared to carbohydrates or proteins. Additionally, fats are lightweight and can be easily stored in the animal's body, allowing them to carry a large energy reserve without adding excessive weight. This makes fats the ideal choice for animals that need to sustain themselves during long migrations.Rate this question:
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- 46.
Certain nutrients are considered "essential" in the diets of some animals because
- A.
Only those animals use those nutrients.
- B.
The nutrients are subunits of important polymers.
- C.
These animals are not able to synthesize these nutrients.
- D.
The nutrients are necessary coenzymes.
- E.
Only certain foods contain them.
Correct Answer
C. These animals are not able to synthesize these nutrients.Explanation
Certain nutrients are considered "essential" in the diets of some animals because these animals are not able to synthesize these nutrients. This means that these animals rely on external sources, such as their diet, to obtain these nutrients. These essential nutrients are necessary for various physiological functions in the animals' bodies, and without them, they may experience deficiencies or health issues. Therefore, it is crucial for these animals to consume foods that provide these essential nutrients since they are unable to produce them internally.Rate this question:
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- 47.
To maintain adequate nutrition, animals require dietary access to certain amino acids. An amino acid that is referred to as "nonessential" would be best described as one that
- A.
Can be made by the animal's body from other substances.
- B.
Is not used by the animal in biosynthesis
- C.
Must be ingested in the diet.
- D.
Is not readily absorbed by the gastrointestinal tract.
- E.
Is not found in many proteins.
Correct Answer
A. Can be made by the animal's body from other substances.Explanation
A nonessential amino acid is one that can be synthesized by the animal's body from other substances, meaning it does not need to be obtained from the diet. This is in contrast to essential amino acids, which cannot be synthesized by the body and must be obtained from the diet. Therefore, the correct answer is that a nonessential amino acid can be made by the animal's body from other substances.Rate this question:
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- 48.
Which pair correctly associates a physiological process with the appropriate vitamin?
- A.
Blood clotting and vitamin C
- B.
Normal vision and vitamin A
- C.
Synthesis of cell membranes and vitamin D
- D.
Protection of skin from cancer and vitamin E
- E.
Production of white blood cells and vitamin K
Correct Answer
B. Normal vision and vitamin AExplanation
Vitamin A is essential for normal vision because it is a key component of the pigment in the retina called rhodopsin. Rhodopsin is responsible for absorbing light in the retina and initiating the visual process. Without sufficient vitamin A, the production of rhodopsin is impaired, leading to night blindness and other vision problems. Therefore, the pair "normal vision and vitamin A" correctly associates a physiological process with the appropriate vitamin.Rate this question:
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- 49.
The fat-soluble vitamins include
- A.
Vitamin A.
- B.
Vitamin B12
- C.
Vitamin C.
- D.
Iodine.
- E.
Calcium
Correct Answer
A. Vitamin A.Explanation
The correct answer is vitamin A. Vitamin A is a fat-soluble vitamin, meaning it dissolves in fat and can be stored in the body's fatty tissues. It is essential for maintaining healthy vision, immune function, and cell growth. Vitamin B12 and vitamin C are water-soluble vitamins, while iodine and calcium are minerals rather than vitamins.Rate this question:
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- 50.
Which pair correctly associates a biochemical process with the appropriate mineral associated with its use in animals?
- A.
Maintenance of bone and calcium
- B.
Cofactor in enzymes that make ATP and magnesium
- C.
Thyroid hormone synthesis and iron
- D.
Nucleic acid synthesis and sulfur
- E.
Glucose homeostasis and iodine
Correct Answer
A. Maintenance of bone and calciumExplanation
The correct answer is maintenance of bone and calcium. Calcium is an essential mineral for the formation and maintenance of bone structure in animals. It is required for bone growth, remodeling, and repair. Calcium also plays a crucial role in muscle contraction, nerve function, and blood clotting. Therefore, the association between maintenance of bone and calcium is correct.Rate this question:
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Mar 20, 2023Quiz Edited by
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