BIOS 1700 Chapter 15

If 8 alleles exist in a population, what is the maximum number of copies a normal individual is expected to have? 3 4 5 8 2

2

In the human copy-number variation (CNV) for the AMY1 gene encoding starch-degrading enzyme, if a homozygous genotype with only one copy of AMY1 in each homologous chromosome produces 1 mg/mL of salivary enzyme, what amount of enzyme would be expected in a heterozygous individual with three copies of the AMY1 gene in one chromosome and two copies of AMY1 in the homologous chromosome? 2.5 mg/mL 5.0 mg/mL 4.5 mg/mL 2.0 mg/mL 3.5 mg/mL

2.5 mg/mL

Diploid somatic cells of elephants have 56 chromosomes. If nondisjunction of one of an elephant's chromosomes occurs in meiosis II, the resulting sperm are expected to have the chromosome complement: 28, 28, 28, 28. 29, 29, 27, 27. 29, 29, 28, 28. 28, 28, 29, 27. 56, 56, 57, 55.

28, 28, 29, 27

Diploid somatic cells of elephants have 56 chromosomes. If nondisjunction of one of an elephant's chromosomes occurs in meiosis I, the resulting sperm are expected to have the chromosome complement: 28, 28, 28, 28. 29, 29, 27, 27. 56, 56, 57, 55. 29, 29, 28, 28. 28, 28, 29, 27.

29, 29, 27, 27

In a population of organisms with 3 alleles, how many homozygous genotypes are possible? How many heterozygous genotypes are possible? 3; 3 3; 4 3; 2 2; 3 2; 1

3;3

How many chromosomes are in a human cell that is triploid? None of the answer options is correct. 92 46 69 23

69

Autosomal trisomies are associated with the X or Y chromosome. True False

False

During the formation of female gametes, nondisjunction of X chromosomes may occur during meiosis I, resulting in two types of eggs with different compositions of sex chromosomes. If normal sperm fertilize these two types of egg, which of the following are possible sex chromosome complements in the resulting fertilized egg? XYY and YO XYY and XO XX and XY XXY and XO XXX and XYY

XXY and XO

Would you consider the SNP associated with sickle-cell hemoglobin to be a risk factor for sickle-cell anemia? Yes, because individuals homozygous for the SNP have the condition. No, because there are many different forms of sickle-cell anemia. No, because sickle-cell anemia is associated with malaria. Yes, although lifestyle choices are also important in the condition. No, because it is a nonsynonymous mutation, not an SNP.

Yes, because individuals homozygous for the SNP have the condition

Ultraviolet light can penetrate the skin and damage DNA, and it can also destroy the B vitamin folate needed for bone-marrow maturation and the development of red blood cells. On the other hand, exposure to ultraviolet light is beneficial in the synthesis of vitamin D3, which is important for growth, calcium absorption, and bone development. The amount of ultraviolet light that penetrates the skin depends on the skin's pigmentation: more melanin (skin pigment) means less penetration. Which of the following do you think would BEST describe the pressure of natural selection on human skin pigmentation? a pressure for darker or lighter skin, depending on the intensity of UV in a geographical region a constant pressure for skin to become more and more pigmented a constant pressure for skin to become less and less pigmented

a pressure for darker or lighter skin, depending on the intensity of UV in a geographical region

The nonmutant allele of the BRCA1 gene helps to suppress tumor formation in women who are heterozygous for the mutation. Women heterozygous for BRCA1 nevertheless have a 50% to 70% chance of developing breast cancer before age 70, and the usual reason is that the nonmutant allele is lost or inactivated in a lineage of cells. One possible mechanism for such "loss of heterozygosity" is: a somatic mutation in a breast cell inactivates the nonmutant BRCA1 allele. germ cells in the affected individual develop a mutation in the nonmutant allele of BRCA1. a silent mutation occurs in the nonmutant BRCA1 allele.

a somatic mutation in a breast cell inactivates the non mutant BRCA1 allele

Which one of the following statements about restriction fragment length polymorphisms (RFLPs) is CORRECT? RFLPs are the product of cleavage by restriction enzymes. RFLPs can take the place of VNTRs in forensic analyses. RFLPs are numerous in the human population. All of these choices are correct. RFLPs are variations in restriction sites that result in DNA being cleaved into different-sized pieces.

all of these choices are correct

When the DNA sequence of the gene that codes for the peptide hormone insulin is compared in two mammals (e.g., humans and rats), most of the sequence differences are synonymous mutations. These far outnumber sequence differences that result in amino acid substitutions. Why might this be? Synonymous mutations occur in noncoding DNA sequences. A DNA sequence is more likely to mutate if the change does not alter the amino acid sequence. Mutations are random with respect to an organism's needs. Most amino acid substitutions result in a beneficial phenotype that improves fitness and results in a greater number of offspring. Amino acid substitutions often result in proteins that have lost or compromised function and, therefore, are selected against.

amino acid substitutions often result in proteins that have lost or compromised function and therefore are selected against

Harmful mutations are often eliminated in a population because they: are fatal to the individual. are repaired. do not confer a benefit to the individual. decrease survival and/or reproduction of the individuals.

decrease survival and/or reproduction of the individuals

Copy-number variation (CNV) can be produced by: (Select all that apply.) inversion. duplication. deletion. frameshift mutation. nonsense mutation.

duplication deletion

Only those mutations that occur in somatic (body) cells can be passed on to progeny. True False

false

Which of the following is true of BOTH first- and second-division nondisjunction? (Select all that apply.) Gametes are produced with missing chromosomes. Gametes are produced with extra chromosomes. Homologous chromosomes fail to separate. Sister chromatids fail to separate. Half of the gametes produced are wild-type, whereas half are mutated.

gametes are produced with missing chromosomes gametes are produced with extra chromosomes

The phenotype of an individual results from an interaction between: genotype and mutation rate. genotype and the environment. allele frequency and mutation rate. allele frequency and the environment. allele frequency and genotype.

genotype and the environment

The lethality of most monosomies and trisomies in humans shows the: advantage of sexual reproduction. importance of gene dosage. deleterious effects of variable number tandem repeat sequences. rarity of gene copy-number variation in the genome.

importance of gene dosage

A male child is born with an XYY constitution of sex chromosomes. The parents are normal XX and XY individuals, so their child's genotype must be the result of nondisjunction in the formation of one of their gametes. When (and in whom) could the nondisjunction have taken place? in the father in meiosis II in the zygote at the first mitotic division in the father in mitosis in the mother in meiosis I in the father in meiosis I

in the father in meiosis ||

For the majority of SNPs implicated in disease, how does carrying a copy affect a person's risk for acquiring that disease? It decreases it dramatically. It decreases it minimally. It decreases it moderately. It increases it dramatically. It increases it moderately.

it increases it moderately

Ultraviolet light is a mutagen, but humans need some exposure to it in order to synthesize vitamin D3. The amount of ultraviolet light that penetrates the skin depends on the skin's pigmentation: more melanin (skin pigment) means less penetration. Certain mutations result in decreased melanin production. Such mutations: may be harmful in one environment and beneficial in another. are neutral only if inherited from one parent, not the other. are beneficial only if inherited from both parents. are harmful only if inherited from both parents.

may be harmful in one environment and beneficial in another

Cancer can be caused by mutations. Genetic analysis of a tumor found in a patient we shall call Anna shows that the cell proliferation was triggered by a somatic mutation in the <i>MYC</i> gene, causing this gene to be inappropriately activated. Anna is concerned about passing this cancer on to the children she plans to have in the future. Should she be concerned? No, she should not worry about her children because this did not occur in a germ-line cell. Yes, she should worry because tumor growth was triggered by a genetic change, and mutations are passed on through cell divisions. No, this is not something to worry about because mutations in cancer cells cannot be passed on in cell division.

no, she should not worry about her children because this did not occur in a germ-line cell

The failure of a pair of chromosomes to separate during anaphase is referred to as: disjunction. translocation. trisomy. inversion. nondisjunction.

nondisjunction

What is a single-nucleotide polymorphism? the presence of single-nucleotides in the DNA double helix a site where a restriction enzyme makes a cut None of the answer options is correct. any point mutation a site where RNA polymerase binds to DNA

none of the answer options is correct

A normal XY male has a son with the karyotype XYY. The likely explanation is: copy-number variation. translocation. first-division nondisjunction. second-division nondisjunction. disjunction.

second-division nondisjunction

What process can account for a normal XY male producing a sperm carrying two Y chromosomes? first-division nondisjunction copy-number variation disjunction translocation second-division nondisjunction

second-division nondisjunction

When DNA with variable number tandem repeats (VNTRs) is visualized on a gel, the resulting fragments separate according to their: color. shape. A-T content. size. G-C content.

size

Which statement BEST explains why embryos with a missing autosome are not always factored into statistics about spontaneously aborted fetuses? The fetus is aborted before the pregnancy is recognized. These embryos do not get aborted but continue to live birth. These embryos occur less often than those with an extra autosome. Fertilization does not occur under these circumstances. None of the other answer options is correct.

the fetus is aborted before the pregnancy is recognized

After doing PCR on the same region between two individuals, you notice that each person's DNA yielded pieces of different sizes. Which of the following is the MOST likely explanation? A mistake was made during gel electrophoresis. A mistake was made during the PCR. This is an example of RFLPs. None of the answer options is correct. This is an example of VNTRs.

this is an example of VNTRs

You are working in a medical research lab and have to determine if a patient is heterozygous or homozygous for a particular restriction site. You isolate a region of DNA from each chromosome, the middle of which could contain the restriction site, if the patient has it. If you treat the DNA with the restriction enzyme, how many fragments will be produced if the patient is heterozygous for the presence of the restriction site? four This question is impossible to answer based on the information provided. three one two

three

Using PCR to amplify the same region of the genome from different individuals can identify differing lengths due to different numbers of repeated sequences referred to as: first-division nondisjunctions. copy-number variations. restriction fragment length polymorphisms. variable number tandem repeats. single-nucleotide polymorphisms.

variable number tandem repeats