Answers to End-of-Chapter Questions – Brooker et al ARIS site
Chapter 16
Test Yourself Questions
1. Based on Mendel’s experimental crosses, what is the expected F
2
phenotypic ratio of a monohybrid cross?
Answer: c. The F
2
generation is the result of crossing F
1
individuals, which are heterozygous. When two heterozygous individuals are crossed the results would be ¾ of the offspring express the dominant phenotype and ¼ of the offspring would express the recessive phenotype.
2. During which phase of cellular division does Mendel’s law of segregation physically occur? c. meiosis II d. all of the above e. b and c only
Answer: b. Mendel’s law of segregation refers to the separation of the two alleles into separate cells.
Meiosis is the cellular division process that produces haploid cells. During the first meiotic division, a diploid cell divides to produce haploid cells. This is the phase in which the two alleles segregate, or separate, from each other.
3. An individual that has two different alleles of a particular gene is said to be
Answer: d. An individual that is heterozygous has two different alleles of a particular gene (e.g., Aa ).
4. Which of Mendel’s laws cannot be observed in a monohybrid cross? c. independent assortment e. All of the above can be observed in a monohybrid cross.
Answer: c. Independent assortment describes how pairs of alleles segregate independently of each other. This requires the observation of two or more pairs of alleles.
5. During a ____ cross, an individual with the dominant phenotype and unknown genotype is crossed with a ______ individual to determine the unknown genotype. a. monohybrid, homozygous recessive c. test, homozygous dominant

d. monohybrid, homozygous dominant e. test, homozygous recessive
Answer: e. A testcross is used to determine the genotype of an individual with the dominant phenotype.
In a test cross, an individual that exhibits the recessive phenotype, and is therefore homozygous recessive, is crossed with the unknown. The ratio of the offspring phenotypes will be used to determine the genotype of the unknown.
6. In humans, males are said to be ______ at X-linked loci.
Answer: e. Because males carry only one copy of X-linked genes, they are said to be hemizygous.
7. A gene that affects more than one phenotypic trait is said to be
Answer: d. Pleiotropy refers to the phenomenon where one gene affects more than one phenotypic trait.
8. A hypothetical flowering plant species produces red, pink and white flowers. To determine the inheritance pattern, the following crosses conducted with the results indicated: red x red  all red white x white  all white x all pink
What type of inheritance pattern does this represent?
Answer: d. Incomplete dominance refers to the inheritance pattern where the heterozygous expresses a phenotype that is intermediate to the homozygotes.
9. Genes located on a sex chromosome are said to be ____________. d. sex-linked .
Answer: d. Sex-linked refers to genes located on the sex chromosomes, either X or Y for example.
Genes located specifically on the X chromosome are X-linked.
10. Genes that are expressed differently depending on whether the individual is male or female are

Answer: c. Sex-influenced genes refer to genes that are autosomal but are expressed differently in males than in females.
Conceptual Questions
1. Define genotype and phenotype. genotype: The genetic composition of an individual. phenotype: The characteristics of an organism that are the result of the expression of its genes.
2. Define autosome. autosomes: The paired chromosomes.
3. Explain why recessive X-linked traits in humans are more likely to occur in males.
Answer: Because males are hemizygous, they may display a recessive trait that is masked by the dominant allele in a heterozygous female. It only takes one recessive allele for the male to display the trait.
Experimental Questions
1. Prior to the Feature Investigation, what was the original purpose of Morgan’s experiments with
Drosophila ?
Answer: Morgan was testing the hypothesis of use and disuse. This hypothesis suggests that if a structure is not used, over time, it will diminish and/or disappear. In Morgan’s experiments, originally he was testing to see if flies reared in the dark would lose some level of eye development.
2. How was Morgan able to demonstrate red-eye color is dominant to white-eye color?
Answer: Using the same methods as Mendel, Morgan crossed a true-breeding strain of red-eye flies with a white-eyed fly. All of the offspring were red-eye indicating that red-eye was the dominant trait.
3. What results led Morgan to conclude that eye color was associated with the sex of the individual?
Answer: When the F
1
individuals were crossed, the ratio was slightly different than the expected
Mendelian ratio. Only male F
2 offspring expressed the white-eye color. At this time, Morgan was aware of sex chromosome differences between male and female flies. He realized that since males only possess one copy of X-linked genes, this would explain why only F
2
males exhibited the recessive trait.
Collaborative Questions
1. Discuss Mendel’s two laws and why they are important.
Answer:
The law of segregation - This law states that the two copies of a gene (alleles) segregate from each other during transmission from parent to offspring. In other words, for each pair of alleles your mother will give you only one and your father will give you only one. This will give you a total of two alleles per

trait. The impact of this law is that in each generation there is a shuffling of genes to get a unique individual.
Independent assortment - This law states that the alleles of each different gene assort randomly during gamete formation. In other words a specific allele for one gene may be found in a gamete regardless of which allele for a different gene is found in the same gamete. This also shuffles the genes and increases the genetic diversity of a species.
2. What are the fundamental principles of the chromosome theory of inheritance?
Answer: a. Chromosomes contain the genetic information that is passed from parent to offspring and from one cell to another. Genes, the basic units of genetics, are found on these chromosomes. b. Chromosomes are replicated and each chromosome retains its individuality (the same number and type of genes) during cell division and gamete formation. c. The nucleus of a diploid cell contains two sets of chromosomes that are found in homologous pairs.
Half of these chromosomes come from the mother and the other half comes from the father and each set of chromosomes carry a full complement of genes. d. During meiosis, one member of each chromosome pair segregates into one daughter nucleus and its homologue segregates into the other daughter nucleus. Each of the resulting haploid cells contain only one set of chromosomes. During the formation of haploid cells, the members of different chromosome pairs segregate independently of each other. e. Gametes are haploid cells that combine to form diploid cells during fertilization, with each gamete transmitting one set of chromosomes to the offspring.

Answers to End-of-Chapter Questions – Brooker et al ARIS site
Chapter 17
Test Yourself Questions
1. Quantitative traits such as height and weight are governed by several genes that usually contribute in an additive way to the trait. This is called c. maternal inheritance.
Answer: e. The inheritance pattern of most quantitative traits is polygenic.
2. When two genes are located on the same chromosome they are said to be
Answer: d. Genes located on the same chromosome are said to be linked.
3. Based on the ideas proposed by Morgan, which of the following statements concerning linkage is not true? a. Traits determined by genes located on the same chromosome are likely to inherit together. b. Crossing over between homologous chromosomes can create new gene combinations. c. Crossing over is more likely to occur between genes that are closer together. d. The probability of crossing over depends on the distance between the genes. e. All but one of the above statements are correct.
Answer: c. Crossing over is less likely to occur between two genes that are closer together.
4. In genetic linkage mapping, one map unit is equivalent to a. one hundred base pairs. b. one base pair. c. 10% recombination frequency. d. 1% recombination frequency. e. 1% the length of the chromosome.
Answer: d. One map unit, or centiMorgan, is equal to one percent recombination.
5. Organelle heredity is possible because a. gene products may be stored in organelles. b. mRNA may be stored in organelles. c. some organelles contain genetic information. d. conjugation of nuclei occurs before cellular division. e. both a and c.
Answer: c. Some organelles, such as mitochondria and chloroplasts, possess DNA molecules with functional genes.

6. In many organisms, organelles such as the mitochondria, are contributed by only the egg. This phenomenon is known as c. maternal effect. d. maternal inheritance. e. both c and d.
Answer: d. Maternal inheritance describes the pattern by which organelles are inherited only through the egg.
7. Modification of a gene during gamete formation or early development that alters the way the gene is expressed during the individual’s lifetime is called a. maternal inheritance. b. epigenetic inheritance. d. multiple allelism.
Answer: b. Epigenetic inheritance describes events that occur before fertilization or in the early stages of development that alter the way a gene will be expressed.
8. When a gene is inactivated during gamete formation and that gene is maintained in an inactivated state in the somatic cells of offspring, such an inheritance pattern is called c. maternal effect. e. polygenic inheritance.
Answer: d. Genomic imprinting is a phenomenon whereby the expression of a gene is dependent on which parent transmits the gene.
9. Calico coat pattern in cats is the result of c. organelle heredity. e. maternal inheritance.
Answer: a. The calico pattern seen in cats and other animals is the result of X-inactivation in a female that is heterozygous for coat color.
10. Maternal effect inheritance can be explained by a. gene products that are given to an egg by the nurse cells. b. the methylation of genes during gamete formation. c. the spreading of X inactivation from the Xic locus. d. the inheritance of alleles that contribute additively to a trait. e. none of the above.
Answer: a. In maternal inheritance, the genotype of the mother determines the phenotype of the offspring. This occurs because the diploid nurse cells provide the egg with their gene products.
Conceptual Questions
1. Define linkage and linkage group.

linkage: The phenomenon of two genes that are close together on the same chromosome tending to be transmitted as a unit. linkage group: A group of genes that usually stay together during meiosis.
2. Explain extranuclear inheritance and give two examples.
Answer: The transmission of genes that are located outside the cell nucleus is called extranuclear inheritance. Two important types of extranuclear inheritance patterns involve genes that are found in mitochondria and chloroplasts. The pigmentation of four o’clock plants involves the inheritance of genes located in the chloroplasts and Leber’s Hereditary Optic Neuropathy in humans involves the inheritance of mitochondrial genes.
3. Define genomic imprinting. genomic imprinting: A phenomenon in which a segment of DNA is imprinted, or marked, in a way that affects gene expression throughout the life of the individual who inherits that DNA.
Experimental Questions
1. What hypothesis were Bateson and Punnett testing when conducting the crosses in the sweet pea?
Answer: Bateson and Punnett were testing the hypothesis that the gene pairs that influence flower color and pollen shape would assort independently of each other. The two traits were expected to show a pattern consistent with Mendel’s law of independent assortment.
2. What were the expected results of Bateson and Punnett’s cross?
Answer: The expected results were a phenotypic ratio of 9:3:3:1. The researchers expected 9/16 of the offspring would have purple flowers and long pollen, 3/16 of the offspring would have purple flowers and round pollen, 3/16 of the offspring would have red flowers and long pollen and 1/16 of the offspring would have red flowers and round pollen.
3. How did the observed results differ from the predicted results? How did Bateson and Punnett explain the results of this particular cross?
Answer: Though all four of the expected phenotype groups were seen, they were not in the predicted ratio of 9:3:3:1. The number of individuals with the phenotypes found in the parental generation (purple flowers and long pollen or red flowers and round pollen) was much higher than expected. Bateson and
Punnett suggested that the gene controlling flower color were somehow coupled with the gene that controls pollen shape. This would explain why these traits did not always assort independently.
Collaborative Questions
1. Discuss two types of gene interactions.
Answer:
Epistasis - this is when one gene prevents the expression of the dominant allele of another gene.
Epistasis often occurs because two or more different proteins are involved in a single cellular function.
As a result, one protein interferes with another which can sometimes lead to unexpected and unpredictable results.
Polygenic inheritance - For most traits the phenotype cannot be sorted into discrete categories and are said to be continuous and show a variation over a range of phenotypes. These traits are sometimes

referred to as quantitative traits which include, in humans, height, weight, skin color and metabolism.
Such continuous traits are polygenic in which several or many genes contribute to the outcome of the trait.
2. Discuss the concept of linkage.
Answer: According to Mendel’s laws, alleles segregate independently of each other. But, this is not always the case. Thomas Hunt Morgan proposed that genes located close to each other on the same chromosome will be inherited as a group. This concept is known as linkage. Research has shown that more offspring have similar parental combinations than would be predicted by independent assortment.
The reason for inheriting this parental combination is due to the fact that crossing-over has not occurred between this set of genes and they are inherited as a unit. The closer two genes are to each other
(therefore the more closely linked they are) the less likely that they will be separated by crossing-over.
Conversely, the farther two genes are from each other the less linked they are and the more likely that that they will be separated by crossing over.

Answers to End-of-Chapter Questions – Brooker et al ARIS site
Chapter 18
Test Yourself Questions
1. Genetic diversity is maintained in bacterial populations by all of the following except
a. fission.
Answer: a. Genetic diversity is primarily maintained by mutation and genetic transfer, which includes conjugation, transformation and transduction.
2. Bacterial cells divide by a process known as
d. fission.
Answer: d. Bacterial cells divide by a process called binary fission.
3. Genetic transfer whereby a bacterial cell takes up bacterial DNA from the environment is
b. fission.
Answer: d. Transformation occurs when a bacterial cell takes up bacterial DNA from the environment.
The DNA was released into the environment by another dying bacterial cell.
4. A bacterial cell can donate DNA during conjugation when it a. produces competence factors. b. contains an F factor. c. is virulent. d. has been infected by a bacteriophage. e. all of the above.
Answer: b. Bacterial cells that contain an F factor can donate DNA during conjugation. Bacterial cells have the potential to acquire F factors from other bacterial cells during conjugation.
5. A bacterial species that becomes resistant to certain antibiotics may have acquired the resistance genes from another bacterial species. This phenomenon of acquiring genes from another species is known as c. horizontal gene transfer. d. vertical gene transfer.

Answer: c. Horizontal gene transfer refers to the transmission of genes from one species to another species.
6. The ___________ is the protein coat of a virus.
Answer: c
7. Among the viruses identified, the characteristics of their genomes show many variations. Which of the following does not describe a typical characteristic of viral genomes? a. The genetic material may be DNA or RNA. b. The nucleic acid may be single stranded or double stranded. c. The genome may carry just a few genes or several dozen. d. The number of copies of the genome may vary. e. All of the above describe typical variation in viral genomes.
Answer: e. There are many genome differences seen in viruses. All of the choices describe a characteristic that varies among the different types of viruses that have been described.
8. During viral infection, attachment is usually specific to a particular cell type because a. the virus is attracted to the appropriate host cells by proteins secreted into the extracellular fluid. b. the virus recognizes and binds to specific molecules in the cytoplasm of the host cell. c. the virus recognizes and binds to specific molecules on the surface of the host cell. d. the host cell produces channel proteins that provide passageways for viruses to enter the cytoplasm. e. the virus releases specific proteins that makes holes in the membrane large enough for the virus to enter.
Answer: c. Viruses usually infect specific cell types because the host cell must have the appropriate cell surface molecules to allow for attachment.
9. HIV, a retrovirus, has a high mutation rate because a. the DNA of the viral genome is less stable than other viral genomes. b. the viral enzyme reverse transcriptase has a high likelihood of making replication errors. c. the viral genome is altered every time it is incorporated into the host genome. d. antibodies produced by the host cell mutate the viral genome when infection occurs. e. all of the above.
Answer: b. Reverse transcriptase, the enzyme that produces a double-stranded DNA molecule from the viral RNA genome, does not have the proofreading ability commonly associated with DNA polymerase.
Without the proofreading capability, the likelihood of mutation increases.
10. A ____________ is an infectious agent solely composed of RNA, whereas, a __________ is an infectious agent solely composed of protein. a. retrovirus, bacteriophage c. prion, virus d. retrovirus, prion

Answer: e. Viroids are single-stranded RNA molecules that cause disease, whereas prions are proteins that cause disease.
Conceptual Questions
1. Define plasmid.
A small, circular piece of DNA that exists independently of the bacterial chromosome.
2. Explain acquired antibiotic resistance and its significance for disease.
Answer: Acquired antibiotic resistance refers to the common phenomenon of a previously susceptible strain becoming resistant to a specific antibiotic. Resistant strains can be significant causes of infection and death among critically ill patients in intensive care units.
3. Explain the steps in a viral reproductive cycle.
Answer: In the first step, the virus attaches to the surface of a host cell. After attachment, the viral genome must enter the host cell. In viruses that are capable of integration, the viral DNA is integrated into the host chromosome. In the case of an RNA virus, the viral genome must be copied into DNA for integration to occur. Next follows the synthesis of viral components by the host cell. These components are then assembled into new viruses. The final stage of the cycle is the release of the new viruses from the cell.
Experimental Questions
1.
What was the hypothesis tested by Lederberg and Tatum?
Answer: Lederberg and Tatum were testing the hypothesis that genetic material could be transferred from one bacterial strain to another.
2. During the Lederberg and Tatum experiment, the researchers compared the growth of mutant strains under two scenarios: mixed strains or unmixed strains. When the unmixed strains were plated on the experimental growth medium, why were no colonies observed to grow? When the mixed strains were plated on the experimental growth medium, a number of colonies were seen to grow. What was the significance of the growth of these colonies?
Answer: The experimental growth medium lacked particular amino acids and biotin. The mutant strains were unable to synthesize these particular amino acids or biotin. Therefore, they were unable to grow due to the lack of the necessary nutrients. The two strains used in the experiment lacked two of four essential nutrients necessary for growth. The appearance of colonies growing on the experimental growth medium indicated that some bacterial cells had acquired the normal genes for the two mutations they carried. By acquiring these normal genes, the ability to synthesize the essential nutrients was restored.
3. The genetic transfer seen in the Lederberg and Tatum experiment could have occurred in one of two ways: taking up DNA released into the environment or contact between two bacterial cells allowing for direct transfer. Bernard Davis conducted an experiment to determine the correct process. Explain the how his results indicated the correct gene transfer process.
Answer: Bernard Davis placed samples of the two bacterial strains in different arms of a U-tube. A filter allowed the free movement of the liquid in which the bacterial cells were suspended, but prevented the actual contact between the bacterial cells. After incubating the strains in this environment, Davis found that genetic transfer did not take place. He concluded that physical contact between cells of the two strains was required for genetic transfer.

Collaborative Questions
1. Discuss the three mechanisms of genetic transfer in bacteria. What is the significance of horizontal genetic transfer.
Answer:
Conjugation – The process involves a direct physical contact between two bacterial cells in which a donor cell transfers a strand of DNA to a recipient cell.
Transformation – This occurs when a living bacteria takes up genetic information which has been released from a dead bacteria.
Transduction – When a virus infects a donor cell, it incorporates a fragment of bacterial chromosomal
DNA into a newly made virus particle. The virus then transfers this fragment of DNA to a recipient cell.
Horizontal gene transfer is the transfer of genes between two different species instead of from one generation to another. Like other forms of gene transfer, these acquired genes sometimes increase survival. Once such example is when one bacterium acquires antibiotic resistance from other bacteria and then itself becomes resistant to that antibiotic.
2. Discuss the steps of viral reproduction.
Answer:
Attachment – The first step is for the virus to attach itself to the surface of the host cell. This attachment is usually specific to one type of cell because the virus recognizes proteins on the surface of the host cell.
Entry – After attachment, the viral genome must enter the host cell. This is accomplished through the injection of the viral DNA or RNA through the plasma membrane of the host cell. In the case of HIV, the envelope fuses with the plasma membrane and both the capsid and its contents are released in the cytosol.
Integration – During this stage, the genetic information is incorporated into the host cell's DNA. This is done via enzymes (e.g., reverse transcriptase and integrase) encoded in the viral genome.
Synthesis of viral components – Once the genetic information is incorporated into the host genome, it will begin replicate itself. Then the viral genetic information begins to build proteins which it will need to assemble new viruses within the host cell.
Viral assembly – After all of the necessary components have been synthesized, they can now be assembled into new viruses. Some simple viruses are capable of self-assembling in which the components of the virus simply bind to each other to form a complete virus particle. Other viruses require a more complex process to assemble the complete virus.
Release – The final stage of viral reproductive cycle is the release of the new virus from the host cell.
Some viruses do this by releasing viral buds from the host cell membrane and the cell doesn’t die. Other viruses cause the host cell to lyse, thereby releasing new viruses and killing the host cell.

Answers to End-of-Chapter Questions – Brooker et al ARIS site
Chapter 19
Test Yourself Questions
1. The process whereby a cell’s morphology and function has changed is called b. cell fate. d. genetic engineering. e. both a and c.
Answer: c. Differentiation is the actual alteration of a cell’s morphology and physiology. Determination is the process that determines what type of differentiation a cell will undergo.
2. Pattern formation in plants is along the __________ axis. e. all of the above.
Answer: d. The first three choices describe the axes involved in animal development. Plant development occurs along the root-shoot axis and in a radial pattern.
3. Positional information is important in determining the destiny of a cell in a multicellular organism.
Cells respond to position information by d. undergoing apoptosis. e. all of the above.
Answer: e. Cells may respond to positional information by all four processes.
4. Morphogens are a. molecules that disrupt normal development. b. molecules that convey positional information. c. mutagenic agents that cause apoptosis. d. receptors that allow cells to adhere to the extracellular matrix. e. both a and c.
Answer: b. Morphogens are molecules that impart positional information and promote developmental changes at the cellular level.
5. What group of molecules plays a key role in controlling the program of developmental changes? a. motor proteins d. restriction endonucleases
Answer: c. A hierarchy of transcription factors is involved in the program that determines developmental changes.

6. Using the list of events below, determine the proper sequence for the events of animal development.
1. Formation of tissues, organs, and other body structures in each segment.
2. Axes of the entire animal are determined.
3. Cells become differentiated.
4. The entire animal is divided into segments. a. 2, 3, 4, 1 b. 1, 2, 4, 3 c. 2, 4, 3, 1 d. 3, 2, 4, 1 e. 2, 4, 1, 3
Answer: e. In animal development, the plan progresses from large to small.
7. The homeotic genes in Drosophila a. determine the structural and functional characteristics of different segments of the developing fly. b. encode motor proteins that transport morphogens throughout the embryo. c. are dispersed apparently randomly throughout the genome. d. are expressed in similar levels in all parts of the developing embryo. e. both a and c.
Answer: a. Homeotic genes produce transcription factors that regulate the gene expression in the different segments thereby determining the structural and functional characteristics of each segment.
8. Which of the following genes do not play a role in the process whereby segments are formed in the fruit fly embryo? c. pair-rule genes d. segment-polarity genes e. All of the above play a role is segmentation.
Answer: a. Homeotic genes do not cause segments to form in the embryo. After the segments form, they cause a segment to develop certain characteristics. Gap genes, pair-rule genes, and segmentpolarity genes are all types of segmentation genes that function during Phase 2 of development.
9. A type of stem cell that can give rise to any type of cell of an adult organism but cannot produce an entire, intact individual is called
Answer: b. Embryonic cells are pluripotent, meaning these cells can produce nearly all types of differentiated cells, but have lost the ability to produce an entire individual.
10. During plant development, the leaves and the flowers of the plant are derived from a. the central region. b. the basal region. c. the suspensor. d. the apical region. e. both a and d.

Answer: d. The apical region gives rise to the leaves and flowers.
Conceptual Questions
1. Define development.
In biology a series of changes in the state of a cell, tissue, organ, or organism; the underlying process that gives rise to the structure and function of living organisms.
2. Explain the hierarchy of gene expression that controls segmentation in Drosophila .
Answer: Maternal effect genes activate gap genes which, in turn, activate pair-rule genes which control segment-polarity genes.
3. What are two characteristics of the proteins that are encoded by homeotic genes that give clues to their function?
Answer: Homeotic proteins have a domain that binds to DNA and a domain that activates transcription.
Homeotic proteins activate transcription of specific genes that promote developmental changes in the animal.
Experimental Questions
1. What was the goal of the research conducted by Davis, Weintraub, and Lasser?
Answer: The researchers were interested in the factors that cause cells to differentiate. For this particular study, the researchers were attempting to identify genes involved in the differentiation of muscle cells.
2. How did Davis, Weintraub, and Lasser’s reaserch identify the candidate genes for muscle differentiation?
Answer: Using genetic technology, the researcher compared the gene expression in cells that could differentiate into muscle cells to the gene expression in cells that could not differentiate into muscle cells.
Though many genes were expressed in both, the researchers were able to isolate three genes that were expressed in muscle cell lines that were not expressed in the non-muscle cell lines.
3. Once the researchers identified the candidate genes for muscle differentiation, how did they test the effect of each gene on cell differentiation? What were the results of the study?
Answer: Again, using genetic technology, each of the candidate genes was introduced into a cell that normally did not give rise to skeletal muscle. This procedure was used to test whether or not these genes played a key role in muscle cell differentiation. If the genetically engineered cell gave rise to muscle cells, the researchers would have evidence that a particular candidate gene was involved in muscle cell differentiation. Of the three candidate genes only one was shown to be involved in muscle cell differentiation. When the MyoD gene was expressed in fibroblasts, these cells differentiated into skeletal muscle cells.
Collaborative Questions
1. Discuss four types of cellular responses that cells can exhibit in response to positional information.
Answer: In multicellular organisms, cells are not independent from each other; they communicate and influence each other. The result of this can vary widely depending on the position and type of cell. One of the results is cell division. Second, positional information in animals may cause the migration of cells or groups of cells in a particular direction from one region of the embryo to another. Third, it may cause

a cell or a group of cells to differentiate into a specific cell type. Finally, a cell's position and interaction with other cells may promote cell death, which is also known as apoptosis.
2. Discuss meristems in plants.
Answer: In plants, there are organized groups of cells which are very active with respect to cell division and producing stem cells. These areas are called meristems. At these areas, cells divide and retain the ability to differentiate into several different types of cells. In plants there are two major places where these meristems are found. First, meristem tissue found in the roots is called the root meristem, which gives rise to the roots and tissue associated with the roots. The second is the shoot meristem which produces all of the aerial parts of the plant such as stems, leaves and flowers.

Answers to End-of-Chapter Questions – Brooker et al ARIS site
Chapter 20
Test Yourself Questions
1. Vectors used to clone genes were derived originally from a. proteins. b. plasmids. c. viruses. d. all of the above. e. b and c only.
Answer: e. Vectors used in gene cloning were originally derived from plasmids and viruses.
2. Restriction enzymes a. are used to cut DNA into pieces for gene cloning. b. are naturally produced by bacteria cells to prevent viral infection. c. produce sticky ends on DNA fragments. d. all of the above. e. a and c only.
Answer: d. Restriction enzymes, also called restriction endonucleases, cut DNA and produce sticky ends on the DNA fragments. These enzymes are naturally produced in some bacteria to prevent viral infection.
3. A DNA library produced by isolating mRNA from a cell and using reverse transcriptase to make DNA molecules is called a __________ library. a. genomic b. mRNA c. proteonomic d. cDNA e. chromosomal
Answer: d. cDNA libraries are produced by isolating mRNAs from a cell and producing DNA molecules using reverse transcriptase.
4. Researchers can identify the colonies that contain the vector with the gene of interest by a. screening the different colonies using a probe that is complementary to the gene of interest. b. keeping records of the particular colonies that were supposedly inoculated with the particular probe. c. using PCR to determine the gene sequence of the DNA in the different colonies. d. using DNA fingerprinting techniques to identify the particular gene of interest. e. none of the above.
Answer: a. During colony hybridization, a probe that is complementary to the gene of interest is used to identify the colonies that contain the appropriate vector.
5. A method used to detect a particular DNA sequence within a mixture of many DNA fragments is a. PCR. c. DNA fingerprinting.

Answer: e. Southern blotting is a method that allows a researcher to detect a particular DNA sequence in a mixture of many DNA fragments.
6. Why is Taq polymerase used in PCR rather than other DNA polymerases? a. Taq polymerase is a synthetic enzyme that produces DNA strands at a faster rate than natural polymerases. b. Taq polymerase is a heat-stable form of DNA polymerase that can function after exposure to high temperatures that are necessary for PCR. c. Taq polymerase is easier to isolate than other DNA polymerases. d. Taq polymerase is the DNA polymerase commonly produced by most eukaryotic cells. e. All of the above.
Answer: b. Taq polymerase is a heat-stable form of DNA polymerase that can function after exposure to high temperatures that are necessary for PCR.
7. The method of determining the base sequence of DNA is a. PCR. b. gene cloning. c. DNA fingerprinting.
Answer: d. DNA sequencing is a method to determine the base sequence of DNA.
8. During bioremediation, microorganisms are used to a. clone genes from eukaryotic organisms. b. introduce correct genes into individuals with genetic diseases. c. decrease pollutants in the environment. d. to produce useful products such as insulin. e. all of the above.
Answer: c. Bioremediation is the use of microorganisms to reduce pollution levels in the environment.
9. Organism that carry genes that were introduced using molecular techniques are called a. transgenics. b. clones. c. mutants. e. both a and d.
Answer: e. An organism that carries genes that were introduced using molecular techniques are called transgenics or genetically modified organisms (GMOs).
10. DNA fingerprinting is used a. to provide a means of precise identification of an organism, such as the identification of specific strains of bacteria. b. as a forensics tool to provide evidence in a criminal case. c. to determine genetic relationships between individuals. d. to determine the identity of an individual. e. all of the above.
Answer: e. DNA fingerprinting is a useful tool that provides a means of identifying individuals and determining genetic relationships between individuals.
Conceptual Questions

1. Define recombinant DNA technology and recombinant DNA.
Recombinant DNA technology: The use of laboratory techniques to isolate and manipulate fragments of
DNA.
Recombinant DNA: Any DNA molecule that has been manipulated so that it contains DNA from two or more sources.
2. Explain how using one restriction enzyme to cut both a plasmid and a gene of interest will allow the gene to be inserted into the plasmid.
Answer: The restriction enzyme cuts the plasmid at a specific site, leaving sticky ends. The gene of interest, cut with the same enzyme, will have complementary sticky ends that allow hydrogen bonding between the gene of interest and the plasmid. The connections are then made permanent using DNA ligase that connects the DNA backbones.
3. Explain how gel electrophoresis separates DNA fragments.
Answer: An electric field is applied across the gel, causing charged molecules to migrate from one side of the gel to the other. The smaller fragments move more quickly than the larger ones. When the run has been completed, the fragments are separated into bands within the gel according to mass.
Experimental Questions
1. What is gene therapy? What is ADA deficiency?
Answer: Gene therapy is the introduction of cloned genes into living cells to correct genetic mutations.
The hope is that the cloned genes will correct or restore the normal gene function and thereby eliminate the clinical effects of the disease.
ADA deficiency is a recessive genetic disorder in which an enzyme, adenosine deaminase, is not functional. The absence of this enzyme causes a buildup of deoxyadenosine which is toxic to lymphocytes. When lymphocytes are destroyed, a person’s immune system begins to fail leading to a severe combined immunodeficiency disease or SCID.
2. In the investigation of Figure 20.20, how did the researchers treat ADA deficiency?
Answer: The researchers introduced normal copies of the ADA gene into lymphocytes, restoring normal cell metabolism. The researchers isolated lymphocytes from the patient and used a viral vector to introduce the gene into the lymphocytes. These lymphocytes were then reintroduced back into the patient.
3. How successful was the gene therapy for ADA deficiency?
Answer: Following several rounds of treatment with gene therapy, researchers were able to document continue production of the correct enzyme by the lymphocytes over the course of four years. However, because the patients were also receiving other forms of treatment, it was not possible to determine if the gene therapy reduced the negative effects of the genetic disease.
Collaborative Questions-
1. Discuss the use of microorganisms for bioremediation.
Answer: Bioremediation is the use of microorganisms to decrease pollutants in the environment.
Enzymes are produced by microorganisms (mostly in bacteria) to break down harmful chemicals to less harmful ones in a process called biotransformation. As a result of this, toxic chemicals can be

transformed into nontoxic ones which is referred to as biodegradation. An example of this is the use of microorganims to treat sewage to break it down into less harmful forms. Another example of biodegradation is the use of microorganisms in the treatment of hazardous chemical wastes.
2. Discuss the process of molecular pharming.
Answer: In molecular pharming, agricultural animals are used to make pharmaceuticals. In most cases domestic livestock such as sheep, cattle, and goats are use to produce proteins in their milk. This is achieved by inserting the desired protein producing gene into the oocyte of the animal to be used. A promoter is also inserted next to the gene so that human gene will be expressed only in the mammary cells. This oocyte is fertilized and implanted into a surrogate mother and the offspring (the transgenic animal) matures. Milk, which contains the desired protein, is then collected and the protein is purified from the milk.