Questions and Answers of Principles of Genetics

What do trp attenuation and the lysine riboswitch have in common?
Would attenuation of the type that regulates the level of trp transcripts in E. coli be likely to occur in eukaryotic organisms?
Operons are common in bacteria but not in eukaryotes. Suggest a reason why.
In bacteria, translation of an mRNA begins before the synthesis of that mRNA is completed. Why is this “coupling” of transcription and translation not possible in eukaryotes?
Muscular dystrophy in humans is caused by mutations in an X-linked gene that encodes a protein called dystrophin. What techniques could you use to determine if this gene is active in different types
Why do steroid hormones interact with receptors inside the cell, whereas peptide hormones interact with receptors on the cell surface?
In the polytene chromosomes of Drosophila larvae (Chapter 6), some bands form large “puffs” when the larvae are subjected to high temperatures. How could you show that these puffs contain genes
How would you distinguish between an enhancer and a promoter?
A polypeptide consists of three separate segments of amino acids, A—B—C. Another polypeptide contains segments A and C but not segment B. How might you determine if these two polypeptides are
What techniques could be used to show that a plant gene is transcribed when the plant is illuminated with light?
When introns were first discovered, they were thought to be genetic “junk”—that is, sequences without any useful function. In fact, they appeared to be worse than junk because they actually
The GAL4 transcription factor in yeast regulates two adjacent genes, GAL1 and GAL10, by binding to DNA sequences between them. These two genes are transcribed in opposite directions on the
Using the techniques of genetic engineering, a researcher has constructed a fusion gene containing the heat-shock response elements from a Drosophila hsp70 gene and the coding region of a jellyfish
Suppose that the segment of the hsp70 gene that was used to make the hsp70/gfp fusion in the preceding problem had mutations in each of its heat-shock response elements. Would the green fluorescent
The polypeptide products of two different genes, A and B, each function as transcription factors. These polypeptides interact to form dimers: AA homodimers, BB homodimers, and AB heterodimers. If the
A particular transcription factor binds to enhancers in 40 different genes. Predict the phenotype of individuals homozygous for a frameshift mutation in the coding sequence of the gene that specifies
The alternately spliced forms of the RNA from the Drosophila doublesex gene encode proteins that are needed to block the development of one or the other set of sexual characteristics. The protein
The RNA from the Drosophila Sex-lethal (Sxl) gene is alternately spliced. In males, the sequence of the mRNA derived from the primary transcript contains all eight exons of the Sxl gene. In females,
In Drosophila, expression of the yellow gene is needed for the formation of dark pigment in many different tissues; without this expression, a tissue appears yellow in color. In the wings, the
What is the nature of each of the following classes of enzymes? What does each type of enzyme do to chromatin?(a) HATs, (b) HDACs, (c) HMTs.
Would double-stranded RNA derived from an intron be able to induce RNA interference?
An RNA interference-like phenomenon has been implicated in the regulation of transposable elements. In Drosophila, two of the key proteins involved in this regulation are encoded by the genes
Suppose that female mice homozygous for the a allele of the Igf2 gene are crossed to male mice homozygous for the b allele of this gene. Which of these two alleles will be expressed in the F1 progeny?
Epigenetic states are transmitted clonally through cell division. What kinds of observations indicate that these states can be reversed or reset?
A researcher hypothesizes that in mice gene A is actively transcribed in liver cells, whereas gene B is actively transcribed in brain cells. Describe procedures that would allow the researcher to
Suppose that the hypothesis mentioned in the previous question is correct and that gene A is actively transcribed in liver cells, whereas gene B is actively transcribed in brain cells. The researcher
Why do null mutations in the msl gene in Drosophila have no effect in females?
Suppose that a woman carries an X chromosome in which the XIST locus has been deleted. The woman’s other X chromosome has an intact XIST locus. What pattern of X-inactivation would be observed
In Drosophila, the variegated phenotype of the white mottled allele is suppressed by a dominant autosomal mutation that knocks out the function of the gene for heterochromatin protein 1 (HP1), an
The sheep Dolly was the first cloned mammal. Dolly was created by implanting a nucleus from a cell taken from the udder of a female sheep into an enucleated egg. This nucleus had two X chromosomes,
How could the CRISPR/Cas9 system be used to create a translocation between two autosomes in cultured human cells?
We discussed the unfortunate effects of insertional mutagenesis in the four boys who developed leukemia after treatment of X-linked severe combined immunodeficiency disease by gene therapy. How might
Insertional mutagenesis is a powerful tool in both plants and animals. However, when performing large-scale insertional mutagenesis, what major advantage do plants have over animals?
How do insertional mutagenesis approaches differ from other reverse genetic approaches?
How can RNAi gene silencing be used to determine the function of genes?
How do the reverse genetic approaches used to dissect biological processes differ from classical genetic approaches?
The first transgenic mice resulted from microinjecting fertilized eggs with vector DNA similar to that diagrammed in Figure 16.15 except that it contained a promoter for the mammalian metallothionein
Richard Meagher and coworkers have cloned a family of 10 genes that encode actins (a major component of the cytoskeleton) in Arabidopsis thaliana. The 10 actin gene products are similar, often
Two men claim to be the father of baby Joyce Doe. Joyce’s mother had her CODIS STR DNA profile analyzed and was homozygous for allele 8 at the TPOX locus (allele 8 contains 8 repeats of the GAAT
Transgenic mice are now routinely produced and studied in research laboratories throughout the world. How are transgenic mice produced? What kinds of information can be obtained from studies
Disarmed retroviral vectors can be used to introduce genes into higher animals including humans. What advantages do retroviral vectors have over other kinds of gene-transfer vectors? What
The generation of transgenic plants using A. tumefaciensmediated transformation often results in multiple sites of insertion. These sites frequently vary in the level of transgene expression. What
The Ti plasmid contains a region referred to as T-DNA. Why is this region called T-DNA, and what is its significance?
Most forensic experts agree that profiles of DNA from blood samples obtained at crime scenes and on personal items can provide convincing evidence for murder convictions.However, the defense
The DNA profiles shown in this problem were prepared using genomic DNA from blood cells obtained from a woman, her daughter, and three men who all claim to be the girl€™s father.Based on
DNA profiles have played central roles in many rape and murder trials. What is a DNA profile? What roles do DNA profiles play in these forensic cases? In some cases, geneticists have been concerned
A group of bodies are found buried in a forest. The police suspect that they may include the missing Jones family (two parents and two children). They extract DNA from bones and examine (using PCR)
A human STR locus contains a tandem repeat (TAGA)n, where n may be any number between 5 and 15. How many alleles of this locus would you expect to find in the human population?
You have constructed a synthetic gene that encodes an enzyme that degrades the herbicide glyphosate. You wish to introduce your synthetic gene into Arabidopsis plants and test the transgenic plants
Human proteins can now be produced in bacteria such as E. coli. However, one cannot simply introduce a human gene into E. coli and expect it to be expressed. What steps must be taken to construct an
In humans, the absence of an enzyme called purine nucleoside phosphorylase (PNP) results in a severe T-cell immunodeficiency similar to that of severe combined immunodeficiency disease (SCID). PNP
Myotonic dystrophy (MD), occurring in about 1 of 8000 individuals, is the most common form of muscular dystrophy in adults. The disease, which is characterized by progressive muscle degeneration, is
How might the characterization of the CF gene and its product lead to the treatment of cystic fibrosis by somatic-cell gene therapy? What obstacles must be overcome before cystic fibrosis can be
How was the nucleotide sequence of the CF gene used to obtain information about the structure and function of its gene product?
Why is the mutant gene that causes Huntington’s disease called huntingtin? Why might this gene be renamed in the future?
What are CpG islands? Of what value are CpG islands in positional cloning of human genes?
A geneticist crosses tall pea plants with short pea plants. All the F1 plants are tall. The F1 plants are then allowed to self-fertilize, and the F2 plants are classified by height: 62 tall and 26
In the following pedigrees, determine whether the trait is more likely to be due to a dominant or a recessive allele.Assume the trait is rare in the population.a.b. IV 5 8. IV
The following pedigree shows the inheritance of a recessive trait. Unless there is evidence to the contrary, assume that the individuals who have married into the family do not carry the recessive
The following pedigree shows the inheritance of a dominant trait. What is the chance that the offspring of the following matings will show the trait: (a) III-1 Ã— III-3;(b) III-2
In a family of six children, what is the chance that at least three are girls?
If four babies are born on a given day: (a) What is the chance that two will be boys and two will be girls?(b) What is the chance that all four will be girls? (c) What combination of boys
If a man and a woman are heterozygous for a gene, and if they have three children, what is the chance that all three will also be heterozygous?
In generation V in the pedigree in Figure 3.15, what is the probability of observing seven children without the cancer-causing mutation and two children with this mutation among a total of nine
In humans, cataracts in the eyes and fragility of the bones are caused by dominant alleles that assort independently. A man with cataracts and normal bones marries a woman without cataracts but with
If both husband and wife are known to be carriers of the allele for albinism, what is the chance of the following combinations in a family of four children: (a) All four unaffected; (b)
Arrange the following events in the correct temporal sequence during eukaryotic cell division, starting with the earliest: (a) condensation of the chromosomes,(b) Movement of chromosomes to the
The following pedigree shows the inheritance of a recessive trait. What is the chance that the couple III-3 and III-4 will have an affected child? II
Peas heterozygous for three independently assorting genes were intercrossed.(a) What proportion of the offspring will be homozygous for all three recessive alleles?(b) What proportion of the
A researcher who has been studying albinism has identified a large group of families with four children in which at least one child shows albinism. None of the parents in this group of families shows
Albinism in humans is caused by a recessive allele a. From marriages between people known to be carriers (Aa) and people with albinism (aa), what proportion of the children would be expected to have
Seed capsules of the Shepherd’s purse are either triangular or ovoid. A cross between a plant with triangular seed capsules and a plant with ovoid seed capsules yielded F1 hybrids that all had
Mendel testcrossed pea plants grown from yellow, round F1 seeds to plants grown from green, wrinkled seeds and obtained the following results: 31 yellow, round; 26 green, round; 27 yellow, wrinkled;
For each of the following situations, determine the degrees of freedom associated with the c2 statistic and decide whether or not the observed c2 value warrants acceptance or rejection of the
A researcher studied six independently assorting genes in a plant. Each gene has a dominant and a recessive allele: R black stem, r red stem; D tall plant, d dwarf plant; C full pods, c constricted
How many different kinds of F1 gametes, F2 genotypes, and F2 phenotypes would be expected from the following crosses:(a) AA × aa;(b) AA BB × aa bb;(c) AA BB CC × aa bb cc?(d) What general formulas
In shorthorn cattle, the genotype RR causes a red coat, the genotype rr causes a white coat, and the genotype Rr causes a roan coat. A breeder has red, white, and roan cows and bulls. What phenotypes
In rabbits, the dominant allele B causes black fur and the recessive allele b causes brown fur; for an independently assorting gene, the dominant allele R causes long fur and the recessive allele r
In mice, the allele C for colored fur is dominant over the allele c for white fur, and the allele V for normal behavior is dominant over the allele v for waltzing behavior, a form of
In pigeons, a dominant allele C causes a checkered pattern in the feathers; its recessive allele c produces a plain pattern. Feather coloration is controlled by an independently assorting gene; the
A woman has a rare abnormality of the eyelids called ptosis, which prevents her from opening her eyes completely. This condition is caused by a dominant allele, P. The woman’s father had ptosis,
A geneticist crossed wild, gray-colored mice with white (albino) mice. All the progeny were gray. These progeny were inter crossed to produce an F2, which consisted of 198 gray and 72 white mice.
Mendel crossed pea plants that produced round seeds with those that produced wrinkled seeds and self-fertilized the progeny. In the F2, he observed 5474 round seeds and 1850 wrinkled seeds. Using the
On the basis of Mendel’s observations, predict the results from the following crosses with peas: (a) A tall (dominant and homozygous) variety crossed with a dwarf variety; (b) The progeny
Arabidopsis plants have 10 chromosomes (five pairs) in their somatic cells. How many chromosomes are present in each of the following: (a) Egg cell nucleus in the female gametophyte, (b)
The mouse haploid genome contains about 2.9 × 109 nucleotide pairs of DNA. How many nucleotide pairs of DNA are present in each of the following mouse cells:(a) Somatic cell, (b) Sperm
In flowering plants, two nuclei from the pollen grain participate in the events of fertilization. With which nuclei from the female gametophyte do these nuclei combine? What tissues are formed from
Given the way that chromosomes behave during meiosis, is there any advantage for an organism to have an even number of chromosome pairs (such as Drosophila does), as opposed to an odd number of
A cell of the bacterium Escherichia coli, a prokaryote, contains one chromosome with about 4.6 million base pairs of DNA comprising 4288 protein-encoding genes. A cell of the yeast Saccharomyces
Are the synergid cells in an Arabidopsis female gametophyte genetically identical to the egg cell nestled between them?
From the information given in Table 2.1 in this chapter, is there a relationship between genome size (measured in base pairs of DNA) and gene number? Explain.
In Arabidopsis, is leaf tissue haploid or diploid? How many nuclei are present in the female gametophyte? How many are present in the male gametophyte? Are these nuclei haploid or diploid?
During meiosis, when does chromosome disjunction occur? When does chromatid disjunction occur?
What visible characteristics of chromosomes indicate that they have undergone crossing over during meiosis?
Does crossing over occur before or after chromosome duplication in cells going through meiosis?
A sperm cell from the fruit fly Drosophila melanogaster contains four chromosomes. How many chromosomes would be present in a spermatogonial cell about to enter meiosis? How many chromatids would be
Match the stages of mitosis with the events they encompass: Stages: (1) Anaphase, (2) Metaphase, (3) Prophase, (4) Telophase. Events: (a) Reformation of the
In what way do the microtubule organizing centers of plant and animal cells differ?
Which typically lasts longer, interphase or M phase? Can you explain why one of these phases lasts longer than the other?
With a focus on the chromosomes, what are the key events during interphase and M phase in the eukaryotic cell cycle?

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