Biology Exam: Could You Pass This Quiz?
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Questions and Answers
- 1.
How did Mendel's studies in genetics differ from earlier studies of breeding and inheritance?
- A.
Mendel worked with plants; earlier studies used animals
- B.
Mendel was able to explain the blending hypothesis
- C.
Mendel's work was more quantitive
- D.
Mendel worked with wild species, not domesticated ones
- E.
Mendel found that offspring inherit characteristics from both parents
Correct Answer
C. Mendel's work was more quantitiveExplanation
Mendel's studies in genetics differed from earlier studies of breeding and inheritance because his work was more quantitative. Unlike earlier studies that relied on qualitative observations, Mendel's experiments involved precise measurements and statistical analysis. He developed the laws of inheritance based on his quantitative data, which laid the foundation for modern genetics. This approach allowed him to establish the principles of dominant and recessive traits, as well as the concept of independent assortment. By quantifying his observations, Mendel provided a more rigorous and scientific understanding of genetics.Rate this question:
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- 2.
A true-breeding fruit fly would be ___ for a certain characteristic.
- A.
Homozygous dominant
- B.
Homozygous recessive
- C.
Heterozygous recessive
- D.
Heterozygous
- E.
A or b
Correct Answer
E. A or bExplanation
A true-breeding fruit fly would be either homozygous dominant or homozygous recessive for a certain characteristic. This means that all the offspring of the true-breeding fly would have the same genotype as the parent for that particular characteristic.Rate this question:
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- 3.
When looking at the inheritance of a single characteristic, Mendel found that a cross between two- true-breeding peas (between purple and white, for example) always yielded a ___ in the F2 generation.
- A.
1:1 phenotypic ratio
- B.
3:1 genpotypic ratio
- C.
1:2:1 phenotypic ratio
- D.
3:1 phenotypic ratio
- E.
1:1 genotypic ratio
Correct Answer
D. 3:1 phenotypic ratioExplanation
Mendel found that when crossing two true-breeding peas with different traits, such as purple and white, the F2 generation always exhibited a 3:1 phenotypic ratio. This means that for every three plants with one phenotype (e.g., purple), there would be one plant with the other phenotype (e.g., white). This result suggests that the trait being observed is controlled by a single gene with two alleles, one dominant and one recessive.Rate this question:
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- 4.
Alternative forms of genes for a particular characteristic are called
- A.
Homologous chromosomes
- B.
Alleles
- C.
Linked genes
- D.
Genotypes
- E.
Phenotypes
Correct Answer
B. AllelesExplanation
Alleles are alternative forms of genes for a particular characteristic. They are different versions of the same gene that can produce different traits or phenotypes. Each individual inherits two alleles for each gene, one from each parent. These alleles can be either dominant or recessive, and they determine the expression of a specific trait in an organism. Therefore, alleles are the correct answer for the given question.Rate this question:
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- 5.
A fruit fly has two genes for eye color, but each of its sperm cells has one. This illustrates
- A.
Independent assortment
- B.
Linked genes
- C.
Pleiotropy
- D.
Polygenic inheritence
- E.
Segregation
Correct Answer
E. SegregationExplanation
Segregation refers to the separation of genes during the formation of gametes. In the case of the fruit fly, it has two genes for eye color, but each sperm cell only carries one gene. This demonstrates the process of segregation, where the genes for eye color are separated and randomly distributed into the sperm cells. This is an example of Mendel's law of segregation, which states that during gamete formation, the alleles for each gene segregate from each other.Rate this question:
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- 6.
Mendel made some crosses where he looked at two characteristics at once- round yellow peas crossed with wrinkled green peas, for example. He did this because he wanted to find out:
- A.
How new characteristics originated
- B.
Whether different characteristics were inherited together or separately
- C.
How plants and animals adapt to their environments
- D.
Whether the characteristics influence each other--whether color affects degree of roundness, for example.
- E.
Actually, Mendel never had a clear purpose in mind
Correct Answer
B. Whether different characteristics were inherited together or separatelyExplanation
Mendel made crosses between round yellow peas and wrinkled green peas to determine whether different characteristics were inherited together or separately. By observing the offspring, he could determine if the traits for roundness and color were linked or if they were inherited independently. This allowed Mendel to understand the principles of inheritance and the concept of dominant and recessive traits.Rate this question:
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- 7.
A pea plant with purple flowers is heterozygous for flower color. Its genotype is Pp. The P and p alleles in the pea plant's cells are located:
- A.
Next to each other on the same chromosome
- B.
At corresponding locations on homologous chromosomes
- C.
On the X and Y chromosomes
- D.
Some distance apart on the same chromosome
- E.
At different locations on homologous chromosomes
Correct Answer
B. At corresponding locations on homologous chromosomesExplanation
The correct answer is at corresponding locations on homologous chromosomes. This is because the pea plant is heterozygous for flower color, meaning it has two different alleles for the trait. These alleles are located at corresponding locations on homologous chromosomes, which are paired chromosomes that contain the same genes but may have different alleles for those genes.Rate this question:
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- 8.
When an individual has both Ia and Ib blood group alleles, both genes are expressed and the individual has group AB blood. This is an example of?
- A.
Codominance
- B.
A dihybrid
- C.
Pleiotropy
- D.
Incomplete dominance
- E.
Linked genes
Correct Answer
A. CodominanceExplanation
When an individual has both Ia and Ib blood group alleles, both genes are expressed and the individual has group AB blood. This is an example of codominance. In codominance, both alleles are fully expressed, resulting in a phenotype that shows traits from both alleles. In this case, the individual expresses both the A and B antigens on their red blood cells, resulting in blood type AB.Rate this question:
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- 9.
How many genes are there on one chromosome?
- A.
One
- B.
Two
- C.
Hundreds
- D.
Thousands
- E.
Millions
Correct Answer
D. ThousandsExplanation
Each chromosome contains thousands of genes. Genes are segments of DNA that contain the instructions for building and maintaining an organism. They determine various traits and characteristics. The human genome, for example, consists of 23 pairs of chromosomes, with each chromosome containing thousands of genes. Therefore, the correct answer is "thousands".Rate this question:
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- 10.
Which of the following is not true of linked genes?
- A.
They tend to be inherited together
- B.
They tend to violate Mendel's principle of independent assortment
- C.
They are on the same chromosome
- D.
They can form new combinations via crossing over
- E.
They are relatively rare; most genes are unlinked.
Correct Answer
E. They are relatively rare; most genes are unlinked.Explanation
Linked genes are genes that are located close to each other on the same chromosome. They tend to be inherited together and violate Mendel's principle of independent assortment because they do not segregate independently during meiosis. They can also form new combinations via crossing over, which is the exchange of genetic material between homologous chromosomes. Therefore, the statement that linked genes are relatively rare and most genes are unlinked is not true.Rate this question:
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- 11.
Morgan and his students were able to map the relative positions of genes on fruit-fly chomosomes by
- A.
Coloring chromosomes with dyes and observing them under a microscope
- B.
Scrambling the chromosomes and observing how the flies changed
- C.
Crossing various flies and looking at the proportions of offspring
- D.
Transplanting chromosomes from one fly to another
- E.
Looking at crosses that showed independent assortment
Correct Answer
C. Crossing various flies and looking at the proportions of offspringExplanation
By crossing various flies and looking at the proportions of offspring, Morgan and his students were able to map the relative positions of genes on fruit-fly chromosomes. This is because the offspring produced from these crosses can exhibit different combinations of traits, allowing researchers to infer the relative positions of genes on the chromosomes. By analyzing the patterns of inheritance in the offspring, they can determine which genes are more likely to be located closer together or farther apart on the chromosomes.Rate this question:
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- 12.
Most sex-linked traits in humans are carried on the __ chromosome, and the recessive phenotypes are seen most often in
- A.
X...women
- B.
X...men
- C.
Y....women
- D.
Y...men
Correct Answer
B. X...menExplanation
Sex-linked traits in humans are carried on the X chromosome. Since men have one X and one Y chromosome, they have a higher chance of expressing recessive phenotypes carried on the X chromosome. This is because they do not have a second X chromosome to mask the effects of the recessive allele. Women, on the other hand, have two X chromosomes, so even if one X chromosome carries a recessive allele, the other X chromosome may carry a dominant allele that masks the recessive phenotype.Rate this question:
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- 13.
The most lethal genetic disease in the USA is
- A.
Sickle-cell disease
- B.
Cystic fibrosis
- C.
Huntington's disease
- D.
Hemophilia
- E.
PKU
Correct Answer
B. Cystic fibrosisExplanation
Cystic fibrosis is the most lethal genetic disease in the USA. It is a progressive disorder that affects the lungs, digestive system, and other organs. It is caused by a mutation in the CFTR gene, resulting in the production of thick, sticky mucus that clogs the airways and leads to respiratory infections. The disease also affects the pancreas, leading to poor digestion and nutrient absorption. Cystic fibrosis has no cure and significantly reduces the life expectancy of affected individuals.Rate this question:
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- 14.
Which of the following human genetic disorders is sex-linked?
- A.
Hemophilia
- B.
PKU
- C.
Cystic fibrosis
- D.
Sickle-cell disease
- E.
All of the above
Correct Answer
A. HemophiliaExplanation
Hemophilia is a sex-linked genetic disorder because it is caused by a mutation in the genes located on the X chromosome. Since males have only one X chromosome, if they inherit the mutated gene, they will develop hemophilia. Females, on the other hand, have two X chromosomes, so they can be carriers of the mutated gene but are less likely to develop the disorder themselves. This pattern of inheritance makes hemophilia a sex-linked disorder.Rate this question:
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- 15.
A brown mouse is mated with a white mouse. All of their offspring are brown. If two of these brown offspring are mated, which fraction of these offspring will be white?
- A.
All
- B.
None
- C.
1/4
- D.
1/2
- E.
3/4
Correct Answer
C. 1/4Explanation
When a brown mouse is mated with a white mouse, all of their offspring are brown. This suggests that the brown color is dominant over the white color. When two brown offspring are mated, they can both carry a recessive white allele from their white parent. Therefore, there is a possibility of their offspring inheriting two white alleles, resulting in a white coat color. Since the brown offspring carry one white allele each, the probability of them passing on this allele is 1/2. Multiplying this probability by 1/2 again (since both parents need to pass on a white allele) gives us 1/4 as the fraction of offspring that will be white.Rate this question:
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- 16.
Suppose you wanted to know the genotype of one of the brown F2 mice in the previous question. The easiest way to do it would be to
- A.
Keep careful records of the parent mice
- B.
Mate it with a brown mouse
- C.
Mate it with a mouse of its own genotype
- D.
Mate it with a white mouse
- E.
It can't be done
Correct Answer
D. Mate it with a white mouseExplanation
To determine the genotype of the brown F2 mouse, mating it with a white mouse would be the easiest way. This is because if the brown mouse is heterozygous (Bb), mating it with a white mouse (bb) would result in offspring that are all brown (Bb). However, if the brown mouse is homozygous dominant (BB), mating it with a white mouse would result in offspring that are a mix of brown and white (Bb). By observing the offspring, the genotype of the brown mouse can be determined.Rate this question:
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- 17.
Some dogs bark while trailing; others are silent. The barker gene is dominant, the silent gene recessive. The gene for the normal tail is dominant over the gene for the screw (curly) tail. A barker dog with a normal tail who is heterozygous for both characteristics is mated to another dog of the same genotype. Which fraction of their offspring will be barkers with screw tails?
- A.
3/4
- B.
9/16
- C.
3/16
- D.
1/4
- E.
1/16
Correct Answer
C. 3/16Explanation
When two heterozygous dogs mate, there is a 1/4 chance of their offspring inheriting both the recessive silent gene and the recessive screw tail gene, resulting in a dog that is silent with a screw tail. This is because the recessive genes can only be expressed when both copies are present. Therefore, the fraction of their offspring that will be barkers with screw tails is 1/4. Since the question asks for the fraction of offspring that will be barkers with screw tails, the correct answer is 3/16, which is equivalent to 1/4.Rate this question:
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- 18.
Two heterozygous tall pea plants with purple flowers are crossed. The probability that one of their offspring will have white flowers is 1/4. The probability that one of their offspring will be short is 1/4. What is the probability that one of their offspring will be short with white flowers?
- A.
0
- B.
1/16
- C.
1/8
- D.
1/4
- E.
1/2
Correct Answer
B. 1/16Explanation
When two heterozygous tall pea plants with purple flowers are crossed, the offspring can inherit different combinations of alleles for height and flower color. The probability of an offspring having white flowers is 1/4, which means that one out of every four offspring is expected to have white flowers. Similarly, the probability of an offspring being short is also 1/4. To find the probability of an offspring being both short and having white flowers, we multiply the probabilities together: 1/4 * 1/4 = 1/16. Therefore, the probability that one of their offspring will be short with white flowers is 1/16.Rate this question:
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- 19.
A young unmarried woman had a baby and wished to collect child support from the father. Her blood group is AB. The baby's blood group is A. There are two possible fathers: Jim is group A, and Michael is a group O. Which man could be the father?
- A.
Either
- B.
Jim
- C.
Michael
- D.
Neither
- E.
Impossible to tell given this evidence
Correct Answer
A. EitherExplanation
Based on the given information, both Jim and Michael could be the father of the baby. The mother has blood group AB, which means she could pass on either the A or B blood type to her child. Since the baby has blood group A, it is possible that the father could have blood type A (Jim) or blood type O (Michael). Therefore, either Jim or Michael could be the father.Rate this question:
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- 20.
Which of the following illustrates pleiotropy?
- A.
In fruit flies, the genes for scarlet eyes and hairy body are located on the same chromosome.
- B.
Matings between earless sheep and long-eared sheep always result in short-eared offspring.
- C.
Wheat kernels can range from white to red in color, a trait controlled by several genes.
- D.
The human cystic fibrosis gene causes many symptoms, from respiratory distress to digestive problems.
- E.
An individual with both IA and IB alleles has blood group AB.
Correct Answer
D. The human cystic fibrosis gene causes many symptoms, from respiratory distress to digestive problems.Explanation
Pleiotropy refers to a single gene having multiple effects or influencing multiple traits. In the case of the human cystic fibrosis gene, it causes a wide range of symptoms that affect multiple systems in the body, including the respiratory and digestive systems. This demonstrates pleiotropy because a single gene is responsible for the development of multiple symptoms and traits.Rate this question:
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- 21.
When two gray-bodied fruit flies are mated, their offspring total 86 gray-bodied males, 81 yellow-bodied males, and 165 gray-bodied females. The allele for the yellow body is
- A.
Sex-linked and dominant.
- B.
Not sex-linked and dominant.
- C.
Sex-linked and recessive.
- D.
Not sex-linked and recessive.
- E.
Impossible to say on the basis of this information.
Correct Answer
C. Sex-linked and recessive.Explanation
Based on the given information, the offspring of two gray-bodied fruit flies consist of 86 gray-bodied males, 81 yellow-bodied males, and 165 gray-bodied females. Since the allele for yellow body is present in both males and females, it is not sex-linked. Additionally, the fact that there are both gray-bodied and yellow-bodied offspring indicates that the allele for yellow body is recessive, as it is masked by the dominant gray-bodied allele. Therefore, the correct answer is that the allele for the yellow body is not sex-linked and recessive.Rate this question:
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- 22.
Red-green color blindness is a human recessive sex-linked trait. A man and a woman with normal vision have a color-blind son. What is the probability that their next child will also be a color-blind son?
- A.
0
- B.
1/8
- C.
1/4
- D.
1/2
- E.
3/4
Correct Answer
C. 1/4Explanation
The probability that their next child will also be a color-blind son is 1/4. This is because color blindness is a recessive trait, meaning that both parents must carry the gene for it in order for their child to be color blind. Since the man is color blind, he must have two copies of the gene. The woman, who has normal vision, must be a carrier of the gene, meaning she has one copy. When they have a child, there is a 1/4 chance that the child will inherit both copies of the gene and be color blind.Rate this question:
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- 23.
On a pedigree tracking the inheritance of PKU, a horizontal line joins a black square and a half black circle. What fraction of this couple's children would you expect to suffer from PKU?
- A.
None
- B.
1/4
- C.
1/2
- D.
3/4
- E.
All
Correct Answer
C. 1/2Explanation
Inheritance of PKU is represented by a black square, which indicates that the individual has the condition. A half black circle represents carriers of the condition. Since the horizontal line joins a black square and a half black circle, it means that one parent has PKU and the other is a carrier. In this case, the couple's children would have a 50% chance of inheriting PKU, as they would either inherit the condition from the affected parent or be carriers like the other parent. Therefore, the expected fraction of the couple's children suffering from PKU is 1/2.Rate this question:
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- 24.
Duchenne muscular dystrophy (DMD) is caused by a sex-linked recessive. Its victims are invariably boys, who usually die before the age of 20. Why is this disorder almost never seen in girls?
- A.
Sex-linked traits are never seen in girls
- B.
The allele is carried on the Y chromosome.
- C.
Nondisjunction occurs in males but not in females.
- D.
Males carrying the alleles don't live long enough to be fathers.
- E.
A sex-linked allele cannot be passed from mother to daughter.
Correct Answer
D. Males carrying the alleles don't live long enough to be fathers.Explanation
Duchenne muscular dystrophy (DMD) is caused by a sex-linked recessive allele. Since the disorder is recessive and located on the X chromosome, girls need to inherit two copies of the allele (one from each parent) to be affected. However, boys only need to inherit one copy of the allele since they have one X and one Y chromosome. As a result, boys are more likely to be affected by DMD. Additionally, the disorder is severe and often leads to early death, which means affected males do not live long enough to pass the allele to their offspring, further reducing the chances of the disorder being seen in girls.Rate this question:
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- 25.
Which of the following would be most useful for preventing a particular genetic disease?
- A.
Knowing how the allele causes phenotypic effects
- B.
Being able to identify carriers
- C.
A test that can determine whether a fetus suffers from a disorder
- D.
Knowing which chromosome bears the allele that causes the disorder
- E.
Tracing the trait back through parents and grandparents
Correct Answer
B. Being able to identify carriersExplanation
Being able to identify carriers would be most useful for preventing a particular genetic disease. Identifying carriers allows for genetic counseling and informed family planning, which can help prevent the transmission of the disease to future generations. By identifying carriers, individuals at risk can be informed and take necessary precautions, such as genetic testing, prenatal screening, or considering alternative reproductive options like adoption or assisted reproductive technologies. This knowledge can also aid in the development of targeted interventions and treatments for carriers, reducing the impact of the disease on affected individuals and their families.Rate this question:
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- 26.
Edward was found to be heterozygous (Ss) for the sickle-cell trait. The alleles represented by S and s are:
- A.
On the X and Y chromosomes
- B.
Linked
- C.
On homologous chromosomes
- D.
Both present in each of Edward's sperm cells
- E.
On the same chromosome but far apart
Correct Answer
C. On homologous chromosomesExplanation
The correct answer is on homologous chromosomes. This means that the alleles represented by S and s are located on the matching pairs of chromosomes that Edward inherited from each of his parents. These homologous chromosomes contain the same genes, but may have different versions of those genes (alleles). In this case, Edward has one copy of the S allele and one copy of the s allele on his homologous chromosomes.Rate this question:
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- 27.
Whether an allele is dominant or recessive depends on:
- A.
How common the allele is, relative to other alleles
- B.
Whether it is inherited from the mother or the father
- C.
Which chromosome it is on
- D.
Whether it or another allele determines the phenotype when both are present
- E.
Whether or not it is linked to other genes
Correct Answer
D. Whether it or another allele determines the phenotype when both are presentExplanation
The dominance or recessiveness of an allele depends on whether it or another allele determines the phenotype when both are present. In other words, if the presence of one allele masks the expression of the other allele, then the former is dominant and the latter is recessive. This is because dominant alleles have the ability to produce a functional protein or trait that overrides the effect of the recessive allele. On the other hand, recessive alleles are only expressed when the dominant allele is not present.Rate this question:
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- 28.
Two fruit flies with eyes of the usual red color are crossed, and their offspring are as follows: 77 red-eyed males, 71 ruby-eyed females, 152 red-eyed females. The allele for ruby color is:
- A.
Autosomal and dominant
- B.
Autosomal and recessive
- C.
Sex-linked and dominant
- D.
Sex-linked and recessive
- E.
Impossible to determine without further information
Correct Answer
D. Sex-linked and recessive -
- 29.
In some of his experiments, Mendel studied the inheritance patterns of two characteristics at once-flower color and pod color, for example. He did this to find out:
- A.
Whether genes for the two characteristics are inherited together or separately
- B.
How many genes are responsible for determining a characteristic
- C.
Whether genes are on chromosomes
- D.
The distance between genes on a chromosome
- E.
How many different genes a pea plant has
Correct Answer
A. Whether genes for the two characteristics are inherited together or separatelyExplanation
Mendel studied the inheritance patterns of two characteristics at once, such as flower color and pod color, to determine whether genes for these characteristics are inherited together or separately. By observing the patterns of inheritance, Mendel could understand if the genes for these characteristics were linked or independent. This helped him establish the principles of inheritance and develop his laws of genetics.Rate this question:
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- 30.
A man who has B blood type and a woman who has A blood type could have children of which of the following phenotypes?
- A.
A or B only
- B.
AB only
- C.
AB or O
- D.
A, B, or O
- E.
A, B, AB, or O
Correct Answer
E. A, B, AB, or OExplanation
A man with B blood type and a woman with A blood type could have children with any blood type because they have different blood types themselves. The man can pass on his B blood type allele, and the woman can pass on her A blood type allele. This means their children could inherit either A, B, AB, or O blood types, depending on which alleles they receive from their parents.Rate this question:
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Mar 17, 2023Quiz Edited by
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Feb 13, 2012Quiz Created by
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