Questions and Answers of Structural Analysis

Figure 1.5 shows a micrograph of chromosomes from a normal human cell. If you created this kind of image using a cell from a person with Down syndrome, what would you expect to see?Figure 1.5 : 1 2 3
Pick any trait you like in any species of wild plant or animal. The trait must somehow vary among different members of the species(see Figure 1.7).When picking a trait to answer this question, do not
How long did it take Mendel to complete the experiment in Figure 2.5?Figure 2.5 Experimental level P plants Tall Dwarf Note: The P cross produces seeds that are part of the Fi generation. Tall Self-
Using Mendel’s data from the experiment in Figure 2.8, conduct a chi square test to determine if the data agree with Mendel’s law of independent assortment.Mendel’s data: THE DATA P cross F1
On rare occasions, an organism may have three copies of a chromosome and therefore three copies of the genes on that chromosome (instead of the usual number of two copies). The alleles for each gene
Outline the steps that occur when piRITS or piRISC silences transposable elements by repressing transcription and by directly inhibiting TE RNAs, respectively. What is the role of piRNAs in this
Explain how the miR-200 family of miRNAs behave as tumorsuppressor genes. What happens when their expression is blocked or decreased?
List five types of cancer in which ncRNAs can be involved.
Explain why viruses are considered nonliving.
What is the role of reverse transcriptase in the reproductive cycle of HIV and other retroviruses?
What is the difference between a temperate phage and a virulent phage?
Describe the process of reverse transcription of HIV RNA.
What is the role of the Vpr protein during the process of HIV DNA integration?
Explain the role of RNase H (a component of reverse transcriptase) during the synthesis of HIV DNA.
Describe how HIV DNA is integrated into a chromosome of the host cell.
Describe how lytic bacteriophages are released from their host cells.
What does a suppressor mutation suppress? What is the difference between an intragenic and an intergenic suppressor?
Why is a host-cell tRNA needed for reverse transcription?
A point mutation occurs in the middle of the coding sequence for a gene. Which types of mutation—silent, missense, nonsense, and frameshift—would be most likely to disrupt protein function and
Cancer are caused by environmental agents that produce mutations in somatic cells. Is an individual with cancer considered a genetic mosaic? Explain why or why not.
Give an example of a mutagen that can change cytosine to uracil.Which DNA repair system(s) would be able to repair this defect?
If a mutagen causes bases to be removed from nucleotides within DNA, what repair system could fix this damage?
With regard to TNRE, what is meant by the term anticipation?
Which step(s) in the double-strand break model for recombination would be inhibited if each of the following proteins was missing?A. RecBCD B. RecA C. RecG D. RuvABC
What two molecular mechanisms can result in gene conversion?Do both occur in the double-strand break model?
What type of DNA structure is recognized by RecG and RuvABC? Do you think these proteins recognize DNA sequences?Be specific about what type(s) of molecular recognition these proteins can perform.
What structure does a restriction enzyme recognize? What type of chemical bond does it cleave? Be as specific as possible.
Write a double-stranded DNA sequence that is 20 bp long and is palindromic.
What is cDNA? How does cDNA differ from genomic DNA in eukaryotes?
Draw the structural feature of a dideoxyribonucleotide that causes chain termination. Explain how it does this.
What is a transgenic organism? Give three examples.
What part of the A. tumefaciens DNA gets transferred to the genome of a plant cell during infection?
Explain the difference between gene modification and gene addition. Is each of the following an example of gene modification or gene addition?A. A mouse model to study cystic fibrosis B.
Discuss some of the worthwhile traits that can be modified in transgenic plants.
Define the following terms: genomics, functional genomics, and proteomics.
Besides the examples listed in Table 23.3, list five types of short sequence elements that a geneticist might want to locate within a DNA sequence.Table 23.3: TABLE 23.3 Short Sequence Elements That
What are the two main functions of tumor-suppressor genes?
Would epigenetic changes that promote cancer be passed to offspring?
W hat would you predict to be the phenotype of a Drosophila larva whose mother was homozygous for a loss-of-function allele in the nanos gene?
How can environmental agents that do not cause gene mutations contribute to cancer?
With regard to biological evolution, which of the following statements is incorrect? Explain why.A. During its lifetime, an animal evolves to become better adapted to its environment.B. The process
With regard to genotypes, what is a true-breeding organism?
Marfan syndrome is a rare inherited human disorder characterized by unusually long limbs and digits plus defects in the heart (especially the aorta) and the eyes, among other symptoms. Following is a
An individual has the genotype Aa Bb Cc and makes an abnormal gamete with the genotype AaBc. Does this gamete violate the law of independent assortment or the law of segregation (or both)?Explain
A true-breeding tall pea plant was crossed to a true-breeding dwarf plant. What is the probability that an F1 individual will be truebreeding?What is the probability that an F1 individual will be a
With regard to sister chromatids, which phase of mitosis is the organization phase, and which is the separation phase?
A species is diploid and has three chromosomes per set. Make a drawing that shows what the chromosomes look like in the G1 and G2 phases of the cell cycle.
Identify the key events during meiosis that result in a 50%reduction in the amount of genetic material per cell.
A cell is diploid and contains three chromosomes per set. Draw the arrangement of the chromosomes during metaphase of mitosis and metaphase of meiosis I and II. In your drawing, make the sets of
The alignment of homologs along the metaphase plate during metaphase of meiosis I is random. In your own words, explain what this means.
A eukaryotic cell is diploid and contains 10 chromosomes (5 in each set). In mitosis and meiosis, how many daughter cells will be produced, and how many chromosomes will each one contain?
Corn has 10 chromosomes per set, and the sporophyte of the species is diploid. If you made karyotypes, what is the total number of chromosomes you would expect to see in each of the following types
A woman with an abnormally long chromosome 13 (and a normal homolog of chromosome 13) has children with a man with an abnormally short chromosome 11 (and a normal homolog of chromosome 11). What is
An allele in Drosophila produces a star-eye trait in the heterozygous individual. However, the star-eye allele is lethal in homozygotes.What would be the ratio of phenotypes of surviving offspring if
A seed dealer wants to sell four-o’clock seeds that will produce only a single color of flowers (red, white, or pink). Explain how this should be done.
Propose the most likely mode of inheritance (autosomal dominant, autosomal recessive, or X-linked recessive) for the disease represented in the following pedigrees. Affected individuals are shown as
A human disease known as vitamin D–resistant rickets is inherited as an X-linked dominant trait. If a male with the disease produces children with a female who does not have the disease, what is
Hemophilia is an X-linked recessive disorder in humans. If a heterozygous woman has children with an unaffected man, what is the probability of each of the following combinations of offspring?A. An
Incontinentia pigmenti, a rare, X-linked dominant disorder in humans, is characterized by swirls of pigment in the skin. If an affected female, who had an unaffected father, has children with an
Scurs in cattle is a sex-influenced trait. A cow with no scurs whose mother had scurs has offspring with a bull with scurs whose father had no scurs. What is the probability of each of the following
In rabbits, the color of body fat is controlled by a single gene with two alleles, designated Y and y. The outcome of this trait is affected by the diet of the rabbit. When raised on a standard
The trait of feathering in fowls is a sex-limited trait controlled by a single gene. Females always exhibit hen-feathering, as do HH and Hh males. Only hh males show cock-feathering. Starting with
The pedigree shown next involves a trait determined by a single gene (affected individuals are shown as filled symbols). Which of the following patterns of inheritance are possible for this trait?A.
Define the term epigenetics, and describe two examples of epigenetic effects.
A maternal effect gene exists in a dominant N (functional) allele and a recessive n (nonfunctional) allele. What are the ratios of genotypes and phenotypes for the offspring of the following
Suppose a maternal effect gene exists as a functional dominant allele and a nonfunctional recessive allele. A mother with the disorder produces all offspring without the disorder. Explain the
Suppose that a maternal effect gene affects the anterior morphology in house flies. The gene exists in a dominant (functional) allele, H, and a recessive (nonfunctional) allele, h, which causes a
Describe three distinct mechanisms for accomplishing dosage compensation in different species.
Describe the molecular process of X-chromosome inactivation.This description should include the three phases of inactivation and the role of the Xic. Explain what happens to the X chromosomes during
On rare occasions, a human male is born who is somewhat feminized compared with other males. Microscopic examination of the cells of one such individual revealed that he has a single Barr body in
Certain forms of human color blindness are inherited as X-linked recessive traits. Hemizygous males are color blind, but heterozygous females are not. However, heterozygous females sometimes have
A black female cat (XBXB) and an orange male cat (XOY) were mated to each other and produced a male cat that was calico.Which sex chromosomes did this male offspring inherit from its mother and
What is the spreading phase of X-chromosome inactivation? Why do you think it is called a spreading phase?
What is a reciprocal cross? Suppose that a gene occurs as a wildtype (functional) allele and a recessive mutant (nonfunctional) allele.What would be the expected outcomes of reciprocal crosses if a
When a chi square test is applied to solve a linkage problem, explain why an independent assortment hypothesis is proposed.
A crossover has occurred in the bivalent shown here.If a second crossover occurs in the same region between these two genes, which two chromatids would be involved to produce the following
A crossover has occurred in the bivalent shown here.What is the outcome of this single crossover? If a second crossover occurs somewhere between A and C, explain which two chromatids would be
A diploid organism has a total of 14 chromosomes and about 20,000 genes per haploid genome. Approximately how many genes are in each linkage group?
By conducting testcrosses, researchers have found that the sweet pea plant has seven linkage groups. How many chromosomes would you expect to find in leaf cells of sweet pea plants?
Though we often think of genes in terms of the phenotypes they produce (e.g., curly leaves, flaky tail, brown eyes), the molecular function of most genes is to encode proteins. Many cellular proteins
Describe the unique features of ascomycetes that facilitate genetic analysis of these fungi.
What is the difference between an F+ and an Hfr strain? Which type of strain can transfer many bacterial genes to recipient cells?
What is the role of the origin of transfer during conjugation involving F+ and Hfr strains? What is the significance of the direction of transfer in Hfr conjugation?
What is the role of sex pili during conjugation?
Think about the structure and transmission of F factors, and discuss how you think F factors may have originated.
Which mechanism of bacterial genetic transfer does not require recombination with the bacterial chromosome?
Explain why small deletions and duplications are less likely than large ones to have a detrimental effect on an individual’s phenotype. If a small deletion within a single chromosome happens to
Explain why inversions and reciprocal translocations do not usually cause a phenotypic effect. Then explain how they can do so in certain cases.
A phenotypically abnormal individual has a phenotypically normal father with an inversion on one copy of chromosome 7 and a phenotypically normal mother without any changes in chromosome structure.
Explain how polytene chromosomes of Drosophila are produced, and describe the six-armed structure they form.
A diploid fruit fly has 8 chromosomes. Which of the following terms should not be used to describe a fruit fly with four sets of chromosomes?A. Polyploid B. Aneuploid C. Euploid D. Tetraploid E. 4n
Which of the following terms should not be used to describe a human with three copies of chromosome 12?A. Polyploid B. Triploid C. Aneuploid D. Euploid E. 2n + 1 F. Trisomy 12
Meiotic nondisjunction usually occurs during meiosis I.What is not separating properly: bivalents or sister chromatids?What is not separating properly during mitotic nondisjunction?
A triploid plant has 18 chromosomes (i.e., 6 chromosomes per set). If we assume that a gamete has an equal probability of receiving one or two copies of each of the 6 types of chromosome, what are
Male honeybees, which are haploid, produce sperm by meiosis. Explain what unusual event (compared with other animals) must occur during spermatogenesis in honeybees to produce sperm. Does this
What is the meaning of the term genetic material?
Draw the structure of a phosphodiester linkage.
Describe how bases interact with each other in the double helix.This description should include the concepts of complementarity, hydrogen bonding, and base stacking.
If one DNA strand is 5′–GGCATTACACTAGGCCT–3′, what is the sequence of the complementary strand?
What is meant by the term DNA sequence?

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