Biology Exam 3 Story Problems

A woman and a man are both heterozygous for a recessive allele for a rare genetic disease. If they have one child, what is the probability that he or she will be affected? If they have two children, what is the probability the second child will be affected? 1/2, 1/4 1/4, 1/2 1/4, 1/4 1/4, 3/4

1/4 and 1/4

In genetics, the dash symbol (-) is a "wild card" that stands for either the dominant allele or the recessive allele; for example, W- means the individual has either the genotype WW or Ww. In summer squash, genotypesW- G- and W- gg are white, ww G- are yellow, and ww gg are green. W and G show independent assortment. What is the ratio of white : yellow : green among progeny of the cross Ww Gg × Ww Gg? 9:6:1 9:3:1 12:3:1 10:3:3

12:3:1

In genetics, the dash symbol (-) is a "wild card" that stands for either the dominant allele or the recessive allele; for example, A- means the individual has either the genotype AA or Aa. Two genes that undergo independent assortment affect the shape of the seed capsule in the broadleaf weed known as shepherd's purse. Each gene has two alleles, one of which is dominant for the shape of the seed capsule. Genotypes of the form A- B-, A- bb, and aa B- have triangular seed capsules, whereas the seed capsules of aa bb genotypes are ovoid. What ratio of triangular : ovoid is expected from the cross Aa Bb × Aa Bb? 13:3 9:7 12:4 15:1 10:6

15:1

A roan cow shows co-dominance in fur color (orange and white). What is the phenotype ratio expected if a roan cow and a roan steer mate together? 1: Orange: 2 Orange and White: 1 White 2 Orange: 2 Orange and White: 0 White 4: Orange and White 1: Orange : 1 White

1: Orange: 2 Orange and White: 1 White

If 8 alleles exist in a population, what is the maximum number of alleles a normal individual is expected to have? 4 2 8 1

2

A plant shows incomplete dominance in size. Tall plants are TT, medium plants Tt and short plants tt. Two medium plants (Tt) are crossed. What fraction of offspring plants will be tall? 25% 50% 100%

25%

You are given two true-breeding groups of gerbils. The gerbils in the first group have black coat color and curly tails; the gerbils in the second group have yellow coat color and straight tails. When you produce an F1generation, you see only gerbils with black coat color and curly tails. When you produce an F2 generation, you see some gerbils with black coat color (75%) and some gerbils with yellow coat color (25%). You also see that some of the gerbils have straight tails (25%) and others (75%) have curly tails. If the single alleles responsible for coat color and tail appearance sort independently, how many of the black gerbils in this generation are expected to have straight tails? 75% 100% 0% 50% 25%

25%

The random alignment of maternal and paternal homologous chromosomes during metaphase I is one of the ways genetic variability among gametes comes about. For example, it is possible for an organism with 4 pairs of homologous chromosomes to produce gametes with up to 16 different combinations of maternal and paternal chromosomes (24 = 16). In the case of humans with 23 pairs of chromosomes, there are over 8 million possible combinations. How many possible combinations of maternal and paternal chromosomes are possible in the gametes of an organism with (2n = 16) chromosomes? 1024 512 16 256 64

256

You have an F2 generation derived from two true-breeding parents with different characteristics for the same trait (determined by a single allele). What percentage of the F2 generation with a dominant phenotype would you expect to be homozygous for your single allele of interest? 0% 100% 33% 75% 25%

33%

Which of the following represents the expected genotypes of an F2 generation consisting of 8 individuals from an initial cross of a true-breeding black (BB) rabbit and a true-breeding white (bb) rabbit? 8 progeny: 0 BB, 0 bb, 8 Bb 8 progeny: 8 BB, 0 bb, 0 Bb 8 progeny: 2 BB, 2 bb, 4 Bb 8 progeny: 4 BB, 4 bb, 0 Bb

8 progeny: 2 BB, 2 bb, 4 Bb

In genetics, the dash symbol (-) is a "wild card" that stands for either the dominant allele or the recessive allele; for example, R- means the individual has either the genotype RR or Rr. In Duroc-Jersey pigs, genotypes R-S- have a red coat color, R- ss and rr S- have sandy-colored coats, and rr ss pigs are white. R and S show independent assortment. What cross is expected to result in all sandy-colored progeny? (Select all that apply.) RR ss × rr ss rr ss × rr ss RR ss × RR ss RR Ss × Rr SS Rr Ss × Rr Ss

A and C

Considering a rare X-linked recessive trait, which of the following statements is/are TRUE? (Select all that apply.) An affected mother is expected to have affected sons. An unaffected woman whose father was affected is expected to have unaffected sons. Both parents have to be affected in order to have affected daughters. An unaffected father is expected to have unaffected daughters. An affected father is expected to have affected daughters.

A and D

Failure of cell division in anaphase in meiosis can result in a: diploid gamete. haploid gamete. diploid fertilized egg. triploid fertilized egg.

A and D

What type of nondisjunction occured if the gametes produced are as follows: two gametes that are normal, and one with n − 1 chromosomes, and one with n + 1 chromosomes. No error occurred; these are normal gametes. A nondisjunction error occurred in meiosis II, in which both sister chromatids of a chromosome migrated to the same pole of the cell. A nondisjunction error occurred in meiosis I, in which both members of a homologous pair migrated to the same pole of the cell. A nondisjunction error occurred in meiosis I, in which both members of all homologous pairs migrated to the same pole of the cell.

A nondisjunction error occurred in meiosis II, in which both sister chromatids of a chromosome migrated to the same pole of the cell

The most frequent kind of mutation, a point mutation, occurs when: None of the other answer options is correct. open reading frames are altered. a single base pair is replaced by another. a block of nucleotides is rearranged.

A single base pair is replaced by another

Point mutations can impair a protein if they result in a: (Select all that apply.) nonsense codon. shift in reading frame. synonymous (silent) codon. nonsynonymous (missense) codon.

A,B,D

The phenylthiocarbamide "taster" allele is denoted PAV and the "nontaster" allele AVI. Heterozygous genotypes are almost all tasters. The frequency of nontasters is low in West Africa but high in India. Based on this information, which allele is expected to be more common in India? A allele AVI allele S allele PAV allele

AVI allele

Processes that regulate cell division in mammals include: rapid degradation of cyclins after CDK activation. activated cyclin-CDK complexes triggering cell cycle events. All of these choices are correct. different cyclins and CDKs acting at different stages of the cell cycle to promote cell division. production of cyclin proteins that activate CDK enzymes.

All

Sexual reproduction results in an increase in genetic diversity because: during prophase I, chromosomes that are paternally and maternally derived recombine so that the gametes have chromosomes that are different from the parents' chromosomes. during fertilization, the gametes that fuse are random so that a large number of chromosomal combinations are possible in the new organism. All of these choices are correct. during metaphase I, the bivalents line up in a random orientation so that gametes inherit a random set of maternally and paternally derived chromosomes.

All

The second meiotic division resembles mitosis because: All of these choices are correct. chromosomes decondense during telophase II. spindle microtubules attach from opposite directions to the centromere of each sister chromatid pair. sister chromatids are separated during anaphase II to become the chromosomes of the daughter cells.

All

Which of these events does NOT include a checkpoint in the cell cycle? the transition from G2 to M phase spindle assembly checkpoint in M phase the transition from G1 to S phase All of these events include a checkpoint in the cell cycle.

All

Cell division is regulated by: signals about the nutritional status of the cell. growth factor signals. All of these choices are correct. signals that indicate that DNA has been replicated. signals that indicate that the cell has reached a sufficient size.

All are correct

In fruit flies, what kind of eye color would be expressed in male progeny from a white-eyed female and a red-eyed male? Half of the male progeny would have red eyes and half of the male progeny would have white eyes (1:1 ratio of eye color in males). All males would have red eyes. All males would have white eyes.

All males would have white eyes

What results did Thomas Hunt Morgan get when he crossed a white-eyed female fly with a red-eyed male fly? All red-eyed flies All white-eyed females and red-eyed males All red-eyed females and white-eyed males All white-eyed flies

All red-eyed females and white-eyed males

Which one of the following would MOST likely contribute to uncontrolled cell proliferation (i.e., cancer)? a mutant DNA replication mechanism causing extra chromosome copies a mutant CDK that was active in the absence of its cyclin binding partner a mutant cyclin that cannot bind to its normal CDK binding partner a mutant enzyme needed for microtubule synthesis/polymerization a mutant kinetochore protein that causes reduced microtubule attachment

B

You investigated the cytoskeleton and found that all three elements, including the one you suspected, are completely normal. You then decide to look at the motor proteins to see if the cause of the abnormality might lie with one of them. Which one of the following would be your hypothesis? The melanophores in these tadpoles have partially functional or nonfunctional kinesin that would normally transport organelles along microfilaments to the center of the cell. The melanophores in these tadpoles have partially functional or nonfunctional dynein that would normally transport organelles along microtubules to the center of the cell. The melanophores in these tadpoles have partially functional or nonfunctional dynein that would normally transport organelles along microfilaments to the center of the cell. The melanophores in these tadpoles have partially functional or nonfunctional myosin that would normally transport organelles along microfilaments to the center of the cell. The melanophores in these tadpoles have partially functional or nonfunctional kinesin that would normally transport organelles along microtubules to the center of the cell.

B

Which of the following describes the result(s) of crossing over that takes place in meiosis I? (Select all that apply.) Homologous chromosomes trade one of their two sister chromatids. The formation of a chiasma. The loss of genetic information from one chromosome and the gain of information by another. The formation of a DNA molecule that is part maternal and part paternal.

B and D

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

B and E

Insertions and deletions of single nucleotides: shorten chromosomes. cause frameshift mutations. cause missense mutations. add or delete amino acids to or from the normal polypeptide.

Cause frameshift mutations

Biologists spend a great deal of time studying the cytoskeleton of cells. Some of the tools they use in their research include chemicals that interfere with the structure of the cytoskeletal elements or with the activities of the motor proteins that associate with the cytoskeleton to facilitate movement. For example, a family of compounds called cytochalasins disrupts the normal assembly and disassembly of microfilaments. Another compound called colchicine binds to tubulin and prevents the assembly of microtubules. A compound known as EHNA (erythro-9-[3-2-(hydroxynonyl)] adenine) interferes with the function of dynein, and blebbistatin inhibits the activity of myosin. Where would you predict colchicine to have the greatest effect? fibroblast migration the shortening of a muscle cell Colchicine would likely have no effect on any of these cells or processes. sperm cell motility chromosome segregation

Chromosome Segregation

In a diploid individual, one chromosome carries A and B genes, and the homologous chromosome carries different forms (alleles) of these same genes, a and b. If there is a single crossover between these two genes involving non-sister chromatids during prophase I of meiosis, the resulting four gametes are: AaBb, AaBb, AaBb, AaBb. AB, ab, AB, ab. AB, AB, ab, ab. AB, Ab, aB, ab. Ab, Ab, aB, aB.

D

Which of the following represents the expected genotypes of an F1 generation consisting of 16 individuals from a cross of a true-breeding black (BB) rabbit and a true-breeding white (bb) rabbit? 16 BB, 0 bb, 0 Bb 8 BB, 8 bb, 0 Bb 4 BB, 4 bb, 8 Bb 0 BB, 0 bb, 16 Bb

D

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: 55, 55, 57, 57. 28, 28, 29, 27. 56, 56, 57, 55. 28, 28, 28, 28. 29, 29, 27, 27.

E

Biologists spend a great deal of time studying the cytoskeleton of cells. Some of the tools they use in their research include chemicals that interfere with the structure of the cytoskeletal elements or with the activities of the motor proteins that associate with the cytoskeleton to facilitate movement. For example, a family of compounds called cytochalasins disrupts the normal assembly and disassembly of microfilaments. Another compound called colchicine binds to tubulin and prevents the assembly of microtubules. A compound known as EHNA (erythro-9-[3-2-(hydroxynonyl)] adenine) interferes with the function of dynein, and blebbistatin inhibits the activity of myosin. Where would you predict cytochalasins to have the greatest effect? sperm cell motility Cytochalasins would likely have no effect on any of these cells or processes. fibroblast migration chromosome segregation the shortening of a muscle cell

Fibroblast Migration

The FoxP2 gene is thought to be involved in language in humans. At prophase I, how many copies of theFoxP2 gene are present in a cell? Keep in mind that humans are diploid. four copies, one on each sister chromatid in a pair of homologous chromosomes eight copies, one on each sister chromatid in a pair of homologous chromosomes two copies, one on each homologous chromosome eight copies, one on each strand of each chromatid per homologous pair

Four copies

A researcher is creating pedigrees for a trait he suspects to be dominant in humans. What are some of the likely features of his pedigrees for families with this trait? Only females will have this dominant trait. The occurrence of mating between individuals with this trait will be high, because all dominant traits are common within any given population. All the offspring of a mating where one parent has the trait will themselves be affected. Generally, no generations will be skipped on this pedigree.

Generally, no generation will be skipped on this pedigree

A human cell with a total of 23 chromosomes is: polyploid diploid haploid aneuploid

Haploid

When X-linked traits are recessive, females will express the traits only if they are _____ for the recessive allele. homozygous heterozygous

Homozygous

A male child is born with an XYY constitution of sex chromosomes. The parents are normal XX and XYindividuals, 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 father in meiosis I in the mother in meiosis I in the father in mitosis

In the father in meiosis II

In a study of tadpole coloration, you noticed that a certain percentage of tadpoles in a population displayed a decreased ability to shift from dark coloration at night to light coloration during the day. These individuals were studied and found to have the normal number of melanophores and these melanophores produced normal amounts of melanin pigment granules. You remember reading that pigment granule transport in melanophores involves the cytoskeleton. Which part of the cytoskeleton would you suggest investigating as a potential source of the faulty color adjustment in these tadpoles? intermediate filaments microtubules microfilaments

Microtubules

Which of the following statements is TRUE regarding nondisjunction? Nondisjunction occurring during meiosis II results in two gametes that completely lack certain chromosomes. Nondisjunction can occur between autosomes or the sex chromosomes. Nondisjunction only occurs during meiosis I or meiosis II, never during mitosis. Nondisjunction only contributes to the development of trisomy 21, not trisomy 13 or 18.

Nondisjunction can occur between autosomes or the sex chromosomes

The most common form of hemophilia is a defect in blood clotting factor VIII, which is caused by a mutant form of a gene on the X chromosome. Boys who inherit that mutation from their mother suffer from uncontrolled bleeding. Girls carrying one copy of this mutation have near normal blood clotting. Uncommonly, a girl is born with hemophilia even though both parents have normal phenotypes. Which of the statements might explain hemophilia in a girl born to parents with normal blood clotting phenotypes? Nondisjunction during egg formation resulted in her receiving two X chromosomes from her mother and an X chromosome from her father; she is XXX. Nondisjunction during egg formation resulted in her receiving no X chromosome from her mother but an X from her father; she is XO. A nondisjunction event in sperm production resulted in her receiving X and Y chromosomes from her father and an X from her mother; she is XXY. Nondisjunction during sperm formation resulted in her receiving no sex chromosome from her father and an X chromosome from her mother; she is XO.

Nondisjunction during sperm formation resulted in her receiving no sex chromosome from her father and an X chromosome from her mother; she is XO.

When in Mitosis does the nuclear envelope breakdown and microtubules contact the chromosomes? telophase prophase anaphase metaphase prometaphase

Prometaphase

Crossing over occurs during which step in meiosis? anaphase II prophase II anaphase I prophase I

Prophase I

Replication of DNA in a eukaryote occurs during which phase of the cell cycle? S phase M phase G1 phase G2 phase

S phase

Which of the following is NOT a way that a mutation can impair a protein? missense (nonsynonymous) codon. nonsense codon. shift in reading frame. silent (synonymous) codon.

Silent Codon

A point mutation that causes no change in the amino acid sequence of a protein is called a: synonymous (silent) mutation. nonsense mutation. nonsynonymous (missense) mutation. stop mutation.

Silent Mutation

Biologists spend a great deal of time studying the cytoskeleton of cells. Some of the tools they use in their research include chemicals that interfere with the structure of the cytoskeletal elements or with the activities of the motor proteins that associate with the cytoskeleton to facilitate movement. For example, a family of compounds called cytochalasins disrupts the normal assembly and disassembly of microfilaments. Another compound called colchicine binds to tubulin and prevents the assembly of microtubules. A compound known as EHNA (erythro-9-[3-2-(hydroxynonyl)] adenine) interferes with the function of dynein, and blebbistatin inhibits the activity of myosin. Where would you predict EHNA to have the greatest effect? fibroblast migration chromosome segregation EHNA would likely have no effect on any of these cells or processes. sperm cell motility the shortening of a muscle cell

Sperm Cell Motility

Biologists spend a great deal of time studying the cytoskeleton of cells. Some of the tools they use in their research include chemicals that interfere with the structure of the cytoskeletal elements or with the activities of the motor proteins that associate with the cytoskeleton to facilitate movement. For example, a family of compounds called cytochalasins disrupts the normal assembly and disassembly of microfilaments. Another compound called colchicine binds to tubulin and prevents the assembly of microtubules. A compound known as EHNA (erythro-9-[3-2-(hydroxynonyl)] adenine) interferes with the function of dynein, and blebbistatin inhibits the activity of myosin. Where would you predict blebbistatin to have the greatest effect? sperm cell motility fibroblast migration chromosome segregation the shortening of a muscle cell Blebbistatin would likely have no effect on any of these cells or processes.

The Shortening of a muscle cell

Recessive alleles in the X chromosome are expressed in males because the Y chromosome does not contain the wild-type allele. No answer text provided. the X chromosome is dominant in males. males are more sensitive to mutations than females.

The Y chromosome does not contain the wild-type alleles

How are Incomplete Dominance and Co Dominance different than a normal Mendelian cross? There is no heterozygous genotype The heterozygous genotype has a unique phenotype There is only one phenotype regardless of genotype There is no difference

The heterozygous genotype has a unique phenotype

Which of the following is NOT true regarding CDKs? The levels of CDK change with the cell cycle. They function as a kinase. They bind to cyclin. They function to control the cell cycle.

The levels of CDK change with the cell cycle

Which of the following statements explains why all of the F1 females from a cross between a red-eyed homozygous female fly and a white-eyed male fly are heterozygous? None of the answer options is correct. The male parent provides them with a white-eye allele in the X, and the female parent provides them with a red-eye allele in the Y. The male parent provides them with a white-eye allele in the X, and the female parent provides them with a red-eye allele in the X. The female parent provides two X chromosomes to each daughter who both carry the red-eye allele. The male parent provides them with a white-eye allele in the X and a red-eye allele in the Y.

The male parent provides them with a white-eye allele in the X, and the female parent provides them with a red-eye allele in the X.

A genotype is: the expression of a trait in an individual. the particular combination of alleles present in a given organism. one of several forms of a gene. the location of a gene on a chromosome.

The particular combination of alleles present in a given organism

A couple has a baby that is monosomic for the X chromosome. This MOST likely occurred during meiosis because: there was an inversion in the X chromosome and crossover occurred. there was nondisjunction of the sister chromatids. there was a duplication in the X chromosome and crossover occurred. there was translocation of part of another chromosome onto the X chromosome.

There was nondisjunction of the sister chromatids

A researcher is evaluating the expression of p53 in cells she is culturing in the laboratory. She notices that in a small group of cells, high levels of phosphorylated p53 occur in the nuclei. What can she deduce about these cells? These cells likely contain damaged DNA. Within these cells, the cell cycle has been halted at the G2/M transition. These cells are normal. All of these cells have entered mitosis.

These cells likely contain damaged DNA

An example of second-division nondisjunction is when sister chromatids fail to separate during anaphase of meiotic cell division. True False

True

The alignment of chromosomes at metaphase of meiosis II is most similar to the alignment of chromosomes during metaphase of mitosis. True False

True

p53 is an example of a: proto-oncogene. oncogene. tumor activator tumor suppressor.

Tumor and Suppressor

A skin cell in G2 of interphase has _____ as much DNA as it had in G1. twice half one fourth four times

Twice

In Mendel's garden peas, each cell in a pea plant has a total of: one allele for each gene, if it has green seeds and two if it has yellow seeds. two alleles for each gene. between one and four alleles for each gene. one allele for each gene.

Two alleles for each gene

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 X or Y-bearing sperm fertilize these two types of eggs, which of the options are possible sex chromosome complements in the resulting fertilized egg? XX and XY or XYY and YO XXX and XO or XXY and YO

XXX, XO, XXY, YO

Huntington's disease is a devastating neurological disorder. If a child of an affected parent receives one copy of the Huntington allele, he or she will develop Huntington's disease. Thus, Huntington's disease is considered _____ trait. a recessive a dominant a neutral a reciprocal

a dominant

An individual that is heterozygous for two linked genes has the genotype A b/a B, which means that the Aand b alleles are in one chromosome and the a and B alleles in the homologous chromosome. Among the products of meiosis listed below, which are the recombinant types? (Select all that apply.) ab Ab aB AB

ab and AB

Most common human traits, such as height, weight, eye color, and hair color, are: incompletely dominant traits complex traits simple traits single gene traits

complex traits

What process allows a gamete to carry a chromosome containing some genes with an allele from the paternal chromosome and other genes with an allele from the maternal chromosome? chromosome duplication crossing over nondisjunction chromosome deletion

crossing over

Lack of exercise is an example of a(n) _____ for/of obesity and diabetes. qualitative trait environmental risk factor genetic risk factor genetic risk factor

environmental risk factor

Genes that are linked do not show: nondisjunction dominance independent assortment segregation

independent assortment

The assembly of what cytoskeletal protein is initiated by the M cyclin-CDK complex? All of these choices are correct actin microfilaments microtubules intermediate filaments

microtubules

Red-green color blindness is due to a mutant gene in the X chromosome. An XX female with normal color vision and an XY male with normal color vision have a child with karyotype XY who is color blind. The likely explanation is that the: mother was homozygous for the color-blind mutation. father was homozygous for the color-blind mutation. father was heterozygous for the color-blindness mutation. mother was heterozygous for the color-blind mutation.

mother was heterozygous for the color-bling mutation

X-linked ichthyosis is a recessive form of a family of skin diseases caused by a hereditary deficiency of the steroid sulfatase (STS) enzyme. A woman heterozygous for this mutation mates with the phenotypically normal man and produces an XXY son who suffers from the disorder. What kind of nondisjunction can explain this result? nondisjunction in meiosis I in the father nondisjunction in meiosis II in the father nondisjunction in meiosis II in the mother nondisjunction in meiosis I in the mother

nondisjunction in meiosis II in the mother

Traits such as human height, blood pressure, and blood sugar levels can be measured along a continuum and are often called _____ traits. qualitative discrete quantitative contradictory

quantitative

You are examining a human pedigree for a trait. You notice that an offspring can be affected even if neither parent is affected. This immediately tells you that the trait is: dominant produced by multiple alleles recessive epistatic

recessive

The two molecules of double-stranded DNA in a replicated chromosome are called: bivalent chromosomes sister chromatids homologous chromosomes non-sister chromatids

sister chromatids

A small difference between concordance rates for a trait in dizygotic twins and monozygotic twins suggests that: variation due to genotype is about equally as important as that due to environment. variation due to genotype is far more important than variation due to environment variation due to genotype is far less important than variation due to environment

variation due to genotype is far less important than variation due to environment