Biology Practice Test (Part 3)

Phenotype refers to the observable traits or characteristics of an organism, which are influenced by both genetic makeup and environmental factors. It is not solely determined by the genetic makeup of an organism. Therefore, the given statement that phenotype refers to the genetic makeup of an organism is incorrect.

DNA microarray is a technique that allows the comparison of gene expression patterns, not protein patterns, between two treatment conditions. It involves the hybridization of labeled DNA fragments to a microarray chip containing thousands of different DNA sequences. This allows researchers to measure the level of gene expression for each gene in the sample and compare it between different conditions. Therefore, the statement that DNA microarray allows the comparison of protein patterns between two treatment conditions is incorrect.

Recombinant DNA research involves the manipulation of genetic material from different organisms, which can pose risks when performed on plants. These risks include the potential for unintended genetic changes, the creation of genetically modified organisms that may have unforeseen effects on the environment or human health, and the potential for gene flow between genetically modified plants and wild populations. Therefore, it is true that there are potential risks in performing recombinant DNA research on plants.

Restriction enzymes are enzymes that cut DNA at specific recognition sites. These enzymes are widely used in biotechnology research to create DNA fragments with precise ends. By cutting DNA at specific sites, restriction enzymes allow researchers to manipulate and analyze DNA sequences. Therefore, the statement that DNA fragments are created by restriction enzymes in biotechnology research is true.

Transgenic animals are indeed those that express DNA derived from another source. This means that these animals have had foreign genes inserted into their genome, resulting in the expression of new traits or characteristics. This process is often used in scientific research to study gene function, develop disease models, or produce specific proteins of interest. Therefore, the statement "Transgenic animals are those which express DNA derived from another" is correct.

In humans, there are indeed 22 pairs of autosomal chromosomes, which are responsible for determining most of our physical traits and characteristics. Additionally, there is one pair of sex chromosomes, which determine the individual's biological sex. This pair consists of two chromosomes, X and Y, with males having one X and one Y chromosome, while females have two X chromosomes. Therefore, the statement "In humans there are 22 pairs of autosomal and one pair of sex chromosomes" is true.

The statement is true because Wallace, along with Charles Darwin, developed the theory of evolution through natural selection. Wallace independently arrived at the same conclusion as Darwin and presented his findings jointly with Darwin in 1858. Their theory proposed that species evolve over time through the process of natural selection, where individuals with advantageous traits are more likely to survive and reproduce, leading to the gradual change and adaptation of species over generations.

Fossils are the remains or traces of organisms that have been preserved in rocks or sediments over time. These preserved organisms leave behind impressions or shapes that resemble their original forms. This is why the correct answer is "bear the impressions or shapes of preserved organisms."

DNA microarray studies do not necessarily need to be hypothesis-driven. This means that researchers can conduct these studies without having a specific hypothesis or question in mind. Instead, they can use microarray technology to analyze and compare gene expression patterns in different samples, allowing for the discovery of new insights and patterns that may not have been anticipated. This exploratory approach can be particularly useful in identifying novel biomarkers or potential therapeutic targets.

Pleiotropy refers to a situation where a single gene influences multiple traits or characteristics. This means that a single gene can have effects on various aspects of an organism's phenotype. For example, a gene may affect both the color of an organism's fur and its susceptibility to a certain disease. Therefore, the statement that pleiotropy occurs when one gene encodes many traits is true.

According to the Law of Segregation, in an organism with the genotype Aa, half of the gametes will have gene A and half will have gene a. This is because during the formation of gametes, the two alleles for a gene separate from each other, so each gamete only carries one allele. Therefore, in this case, half of the gametes will carry the dominant allele A and half will carry the recessive allele a.

A recessive gene is one that is expressed less strongly than a dominant allele. This means that the effect of the recessive gene is hidden or masked by the presence of a dominant allele. In other words, the dominant allele "overrides" the expression of the recessive gene, making it appear as if the individual only has the dominant trait. This is why individuals with a heterozygous genotype (having both a dominant and recessive allele) may not show the recessive trait, as the dominant allele masks its effect.

The correct answer is "overpopulation is not good." Thomas Malthus, an economist and demographer, proposed that overpopulation can lead to negative consequences such as famine, poverty, and social unrest. He argued that population growth would outpace the availability of resources, leading to a decline in living standards. Malthus' ideas were influential in shaping discussions on population and resource management.

A locus refers to the specific location or position of a gene on a chromosome. It is used to describe the region of the chromosome that a gene occupies. The term "phenotype" refers to the observable characteristics or traits of an organism, and it is not directly related to the location of a gene. "Spindle fibers" and "centrioles" are structures involved in cell division and are not related to the location of a gene on a chromosome. Therefore, the correct answer is locus.

When the gene for tall plants is incompletely dominant over the gene for short plants, crossing two Tt plants would result in a phenotypic ratio of 25% tall, 50% intermediate, and 25% short. This is because the T allele is not completely dominant over the t allele, resulting in an intermediate phenotype in heterozygous individuals (Tt).

DNA restriction enzymes are proteins. These enzymes are responsible for cutting DNA molecules at specific sequences, known as restriction sites. They play a vital role in genetic engineering and biotechnology, as they allow scientists to manipulate and study DNA. Proteins are made up of amino acids and are essential for various biological processes in living organisms.

A DNA microarray study is a technique used to analyze the expression levels of thousands of genes simultaneously. It involves measuring the upregulation (increased expression) or downregulation (decreased expression) of mRNA molecules, which are the intermediates between DNA and proteins. By studying these changes in gene expression, researchers can gain insights into various biological processes, such as identifying potential biomarkers for diseases or understanding the effects of certain treatments. Therefore, the correct answer is upregulations and downregulations of mRNA molecules.

The correct answer is Darwin because he is the author of the book "On the Origin of Species." Darwin's work revolutionized the field of biology and introduced the theory of evolution by natural selection. His book presented evidence for the idea that species evolve over time through a process of adaptation to their environment. Darwin's theory had a profound impact on the scientific community and continues to be widely accepted today.

If the allele for inflated pea pods (I) is dominant to the allele for constricted (i), the cross Ii x ii is expected to produce half with inflated and ¼ with constricted pods. This is because when the genotype of one parent is Ii (heterozygous), it will have one dominant allele (I) and one recessive allele (i). When it is crossed with another parent with the genotype ii (homozygous recessive), all of the offspring will inherit one recessive allele from the ii parent. Therefore, half of the offspring will have the genotype Ii (inflated pods) and ¼ of the offspring will have the genotype ii (constricted pods).

The given question is asking for the combination of gametes that is NOT possible in an organism that is AaBb. The genotype AaBb indicates that the organism has two different alleles for each gene, so it can produce four different types of gametes: AB, Ab, aB, and ab. Therefore, the only combination that is NOT possible in this case is aa, as it would require both alleles to be the same.

Plasmids are small self-replicating DNA molecules in bacteria. They are separate from the bacterial chromosome and can replicate independently. Plasmids often carry genes that provide advantages to the bacteria, such as antibiotic resistance or the ability to metabolize certain substances. Due to their self-replicating nature, plasmids can be transferred between bacteria through horizontal gene transfer, allowing the spread of these advantageous genes. Therefore, the correct answer is small self-replicating DNA molecules in bacteria.

The given sequence "ACGGACGGACGG" contains three Short Tandem Repeats (STRs). STRs are sequences of DNA that consist of a short pattern of nucleotides repeated multiple times in a row. In this sequence, the pattern "ACGG" is repeated three times consecutively, making it an STR. Therefore, the correct answer is 3.

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The genetic makeup of an individual refers to the combination of genes that they inherit from their parents. This combination determines their unique traits and characteristics. Therefore, the correct answer is "genotype" as it accurately describes the genetic composition of an individual.

The birth of recombinant DNA technology was led by the discovery of DNA restriction enzymes, DNA ligase, and plasmids as a vehicle for gene transfer. DNA restriction enzymes are used to cut DNA at specific sequences, allowing for the insertion of foreign DNA. DNA ligase is then used to join the cut DNA fragments together. Plasmids, which are small circular DNA molecules, can be used as a vehicle to transfer genes between different organisms. Therefore, all of the above discoveries played a crucial role in the development of recombinant DNA technology.

Polygenic inheritance occurs when the expression of a trait is influenced by the action of many genes. In this pattern of inheritance, multiple genes contribute to the phenotype, and each gene has a small additive effect. This results in a continuous variation of the trait, as opposed to the distinct categories seen in complete dominance or discontinuous variation. Incomplete dominance refers to a pattern where neither allele is dominant over the other, while pleiotropy refers to a single gene influencing multiple traits.

According to the Aristotle ladder of Nature, evolution could not occur as the position of each living thing is fixed. This means that Aristotle believed that species were fixed and unchanging, and that each species had a specific place in the natural order that could not be altered through evolution. Therefore, the correct answer is that evolution could not occur.

Peas were a good organism of choice for Mendel because he could study one trait at a time. This allowed him to isolate and analyze the inheritance patterns of specific traits without the complication of multiple traits interacting simultaneously. By focusing on one trait at a time, Mendel was able to establish the principles of inheritance and develop his laws of segregation and independent assortment.

A population is defined as all individuals of the same species that are located in a specific region of the world at the same time. This definition emphasizes the spatial and temporal aspects of a population, indicating that it consists of individuals of the same species that are present in a particular area during a specific period. It excludes individuals of the same species located throughout the entire world or individuals of all species. Additionally, it does not require that the individuals have an identical genetic makeup, as genetic variation can exist within a population.

If some of the offspring of a dominant individual show the recessive phenotype, it suggests that the dominant individual is heterozygous (Dd) for the trait. This is because the recessive phenotype can only be expressed if an individual carries two copies of the recessive allele (dd), which can only happen if one parent passes on the recessive allele. Therefore, the genotype of the dominant individual must be Dd.

PCR stands for Polymerase Chain Reaction, which is a molecular technique that involves replicating DNA in a test tube. It is a widely used method in molecular biology and genetics to amplify a specific DNA sequence. PCR involves a series of temperature changes to denature the DNA, anneal primers, and extend the DNA using a DNA polymerase enzyme. This process allows for the exponential amplification of a specific DNA region, making it useful for various applications such as DNA sequencing, genetic testing, and gene expression analysis.

All of the options listed are examples of recombinant DNA technology. Herbicide resistant corn, Bt-toxin producing soybean, banana vaccine against pathogenic E. coli, and human insulin produced by bacteria are all products that have been created using recombinant DNA technology. This technology involves combining DNA from different sources to create new genetic combinations with desired traits or functions. In each of the given examples, DNA from different organisms has been manipulated and combined to produce the desired traits or products.

DNA microarray is the most likely method to be useful for identifying upregulated and downregulated mRNAs in a disorder. DNA microarray technology allows for the simultaneous measurement of the expression levels of thousands of genes in a single experiment. By comparing the gene expression profiles of healthy and diseased tissues, researchers can identify genes that are differentially expressed, indicating potential upregulation or downregulation. This method provides a comprehensive and high-throughput approach to analyze gene expression patterns and can help identify potential biomarkers or therapeutic targets for the disorder.

A yellow color spot in DNA microarray indicates equal mRNA synthesis between the two conditions being compared. This means that the expression levels of the genes in both conditions are the same, suggesting that there is no significant difference in gene expression between the two conditions. This information is valuable in understanding the similarities and differences in gene expression profiles between different samples or experimental conditions.

The polymerase chain reaction (PCR) is a technique used to amplify a specific DNA sequence. It involves three steps: denaturation, annealing, and extension. During denaturation, the DNA strands are separated by heating. In the annealing step, primers bind to the target DNA sequence. Extension is the step where DNA polymerase synthesizes new DNA strands using the primers as a template. Retraction is not a step in PCR and is therefore the correct answer.

Segregation refers to the separation of alleles during the formation of gametes. When alleles move into different gametes, it indicates that they are segregating and being separated from each other. This process is a fundamental principle of Mendelian genetics and explains how traits are passed on from parents to offspring. During segregation, each gamete receives only one allele for a particular trait, resulting in the inheritance of either the dominant or recessive allele by the offspring.

The correct answer is A & B & C. Experts study evolution using comparative anatomy, biogeography, and genetics and biochemical analysis. Comparative anatomy helps in understanding the similarities and differences in the anatomical structures of different species, which can provide insights into their evolutionary relationships. Biogeography examines the distribution of species across different geographical regions and how it has changed over time, contributing to our understanding of how species have evolved and dispersed. Genetics and biochemical analysis involve studying the genetic information and molecular processes in organisms, which can reveal evolutionary patterns and relationships.

When two pea plants that are heterozygous for yellow seed color genes are crossed, the expected ratio of yellow to green among the offspring will be 75% yellow and 25% green. This is because the yellow seed color is dominant over the green seed color. The heterozygous plants have one dominant allele for yellow seed color and one recessive allele for green seed color. When these plants are crossed, there is a 25% chance that both parents will contribute the recessive allele, resulting in green offspring. The remaining 75% of the offspring will have at least one dominant allele for yellow seed color, making them yellow.

Short tandem repeats (STRs) are currently used to produce genetic "fingerprints" of people. STRs are regions of DNA that contain short sequences of repeating nucleotides. These repeating sequences vary in length and are unique to each individual. By analyzing the number and pattern of STRs in a person's DNA, a genetic fingerprint can be created. This method is commonly used in forensic science and paternity testing to determine the identity or relatedness of individuals.

The correct answer is pigments. The question mentions that in the chromatography lab, you isolated lipids, nucleic acids, pigments, and carbohydrates. However, the question is asking for the correct answer, which is only pigments.

In owl pellets, the most common items found are hair and bone. Owls regurgitate pellets containing undigested remains of their prey, such as bones and fur. Muscle is not typically found in owl pellets as it is usually digested by the owl's digestive system. Therefore, the correct answer is "only A & C" which refers to hair and bone.

In Owl, digestible food gets separated from non-digestible (i.e, feathers, bones, teeth) in the ventriculus.

PCR (Polymerase Chain Reaction) is a technique that amplifies a specific region of DNA. It involves a series of temperature changes to denature the DNA, allow primers to bind, and then extend the DNA using a heat-stable DNA polymerase enzyme. This process is repeated multiple times, resulting in exponential amplification of the target DNA region. Gel electrophoresis is used to separate DNA fragments based on size, DNA probes are used to detect specific DNA sequences, and DNA profiles are used for genetic identification, but these techniques do not specifically amplify a region of DNA like PCR does.

Evolution refers to the process of change in the genetic composition of a population over a period of time. This change occurs through the mechanisms of mutation, genetic recombination, and natural selection. It does not involve an individual transforming into a different species or changing into a beast. Therefore, the correct answer is "a change in the genetic makeup of a population over time."

Both Darwin and Wallace independently developed and proposed the theory of evolution by natural selection. While Darwin is widely known for his work on the theory, Wallace also made significant contributions to its development. Wallace's ideas on natural selection closely paralleled Darwin's, and their joint effort led to the publication of the famous paper on the subject in 1858. Although Darwin's book "On the Origin of Species" became more widely recognized, Wallace's contributions to the theory of evolution are highly regarded by scientists.

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The gene pool is defined as all the alleles that occur in that population. This means that it includes all the different versions of genes present in a particular population. It encompasses both dominant and recessive alleles, as well as any variations or mutations that may exist within the population. The gene pool represents the total genetic diversity within a population and is important for understanding how traits are inherited and how populations evolve over time.

The correct answer is A & B. DNA microarray is a large-scale screening method used for gene expression profiling. It allows researchers to simultaneously analyze the expression levels of thousands of genes in a single experiment. This technique is useful in identifying genes that are upregulated or downregulated under specific conditions or in different cell types. Additionally, DNA microarrays can also be used for gene cloning, as they provide a way to isolate and amplify specific genes of interest. Therefore, options A and B accurately describe the applications of DNA microarray.

In the chromatography lab, absorbance is measured using different wavelengths. Absorbance refers to the amount of light absorbed by a substance, and it is commonly used to determine the concentration of a compound in a solution. By measuring absorbance at different wavelengths, scientists can obtain information about the specific compounds present in a sample and their concentrations. Reflection, deflection, and refraction are not directly related to measuring absorbance in chromatography.

Restriction enzymes are useful in recombinant DNA studies because they have the ability to cut DNA at specific locations. This allows scientists to precisely manipulate and modify DNA molecules, such as inserting genes into plasmids or cutting out specific segments of DNA. By cutting DNA at specific locations, restriction enzymes facilitate the creation of recombinant DNA molecules, which are essential for genetic engineering and biotechnology applications.