exam 1 answer key - genetics

C - nondisjunction occurs when homologous chromosomes fail to seperate during anaphase 1

Nondisjunction refers to the failure of chromosomes to separate properly during cell division. Select the statement that best describes nondisjunction during meiosis I.

a. Nondisjunction happens when sister chromatids fail to separate during anaphase I.

b. Nondisjunction can occur during any stage of meiosis I.

c. Nondisjunction occurs when homologous chromosomes fail to separate during anaphase I.

d. Nondisjunction occurs when homologous chromosomes fail to separate during metaphase I.

e. Nondisjunction happens when sister chromatids fail to separate during metaphase I.

A - Both X chromosomes would be active.

Assume that an XX mouse is homozygous for a mutation in the Xist gene that causes the gene to not be expressed. What would be the expected consequences of such a situation?

  a.  Both X chromosomes would be active.

  b.  The mouse would have two Barr bodies instead of one.

  c.  The mouse would have a Y chromosome.

  d.  The mouse would develop as a male.

  e.  Nondisjunction would occur at each meiotic event.

e. 1/32

If an AaBbccDd individual is crossed to an AaBbCcDD individual, what is the probability that they produce an offspring with the genotype AabbccDd?

  a.  3/64

  b.  1/64

  c.  1/8

  d.  1/16

  e.  1/32

c. DNA will be replicated.

. If a healthy cell passes the G1/S checkpoint

a. it will proceed immediately to cytokinesis.

b. it will die.

c. DNA will be replicated.

d. it will not divide.

e. it will enter the G0 stage of the cell cycle.

e. gene.

The fundamental unit of heredity is the

a. chromosome.

b. allele.

c. phenotype.

d. nucleus.

e. gene.

a. one gene pair with incomplete dominance

In the endangered African watchamakallit, the offspring of a true-breeding black parent and a true-breeding white parent are all gray. When the gray offspring are crossed among themselves, their offspring occur in a ratio of 1 black : 2 gray : 1 white. What is the mode of inheritance?

a. one gene pair with incomplete dominance

b. one gene pair with black dominant to white

c. one gene pair with codominance

d. two gene pairs with recessive epistasis

e. two gene pairs with duplicate genes

a. 1:2:1

If two heterozygous Aa plants are crossed with each other, what will be the genotypic ratio found in the offspring?

  a.  1:2:1

  b.  1:1

  c.  3:1

  d.  2:1

  e.  1:1:1:1

c. recessive epistasis

Hair color is determined in Labrador retrievers by alleles at the B and E loci. A dominant allele B encodes black pigment, whereas a recessive allele b encodes brown pigment. Alleles at a second locus affect the deposition of the pigment in the shaft of the hair; dominant allele E allows dark pigment (black or brown) to be deposited, whereas recessive allele e prevents the deposition of dark pigment, causing the hair to be yellow. What type of gene interaction does this represent?

  a.  duplicate dominant epistasis

  b.  dominant epistasis

  c.  recessive epistasis

  d.  duplicate recessive epistasis

  e.  dominant and recessive epistasis

  e.  transmission genetics

The experiments of Gregor Mendel can be placed into which subdivision of genetics?

a. molecular genetics and transmission genetics

b. population genetics and transmission genetics

c. population genetics

d. molecular genetics

e. transmission genetics

a. Two cells would have three chromosomes, and two cells would have five chromosomes.

A "mistake" is happening during meiosis I in the following figure. Assume the second meiotic division is normal. How many chromosomes would be expected in the four cellular products of this meiotic event?

a. Two cells would have three chromosomes, and two cells would have five chromosomes.

b. All four cells would have four chromosomes.

c. Two cells would have six chromosome, and two cells would have 10 chromosomes.

d. One cell would have three chromosomes, one cell would have five chromosomes, and two cells would have four chromosomes.

e. All four cells would have three chromosomes.

  c.  BB ee

Hair color is determined in Labrador retrievers the Black and Extension loci. A black female Labrador retriever was mated with a yellow male. Half of the puppies were black, and half were yellow. If the genotype of the black female parent was Bb Ee, then what was the genotype of the other parent?

  a.  bb ee

  b.  bb EE

  c.  BB ee

  d.  Bb ee

  e.  BB EE

c. 1/16

 Round seeds (R) are dominant to wrinkled seeds (r), and yellow seeds (Y) are dominant to green seeds (y). A true-breeding pea plant with round and yellow seeds is crossed to a true-breeding plant with wrinkled and green seeds. The F1 progeny are allowed to self-fertilize. What is the probability of obtaining a wrinkled, green seed in the F2?

  a.  3/4

  b.  1/2

  c.  1/16

  d.  3/16

  e.  9/16

  b.  The genotype must be Bb.

In horses, black coat color is dominant to brown. Suppose that a black horse is mated with a brown one and has two offspring, one black and one brown. What can you conclude about the genotype of the black parent?

  a.  The genotype cannot be determined from these data.

  b.  The genotype must be Bb.

  c.  The genotype could be either BB or Bb.

  d.  The genotype must be bb.

  e.  The genotype must be BB.

b. during meiosis I, anaphase

In a germ-line cell from a female grasshopper (XX-XO sex determination system), when do the homologous X chromosomes segregate?

a. during meiosis II, anaphase

b. during meiosis I, anaphase

c. They do not segregate; gametes contain a copy of X and a copy of Y.

d. during mitosis

e. just before meiosis begins

d. population genetics

Which of the following is fundamentally the study of evolution?

a. ecology

b. transmission genetics

c. heredity

d. population genetics

e. molecular genetics

e. 1

How many genetic alterations are necessary to cause albinism?

a. none

b. 5 or more

c. 50 or more

d. at least 10

e. 1

b. 3 full color : 1 chinchilla

 In rabbits, an allelic series helps to determine coat color: C (full color), cch (chinchilla; gray color), ch (Himalayan; white with black extremities), and c (albino; all white). The C allele is dominant to all others, cch is dominant to ch and c, ch is dominant to c, and c is recessive to all the other alleles. This dominance hierarchy can be summarized as C > cch > ch > c. Indicate the phenotypic ratios expected of rabbits with the cross Ccch × Cch.

  a.  1 full color : 1 chinchilla

  b.  3 full color : 1 chinchilla

  c.  2 full color : 1 Himalayan : 1 albino

  d.  1 full color : 1 Himalayan

  e.  1 chinchilla : 1 Himalayan

b. 21

A diploid somatic cell from a rat has a total of 42 chromosomes (2n = 42). As in humans, sex chromosomes determine sex: XX in females and XY in males. What is the total number of chromosomes in a polar body cell from a rat?

  a.  42

  b.  21

  c.  84

  d.  41

  e.  40

b.  1/8

In Drosophila yellow body color is caused by a sex-linked recessive allele and brown eye color is an autosomal recessive trait. A phenotypically normal female fly, heterozygous for both genes, is crossed to a male with normal body color and brown eyes. What proportion of their offspring should have yellow body color and brown eyes?

  a.  3/8

  b.  1/8

  c.  1/16

  d.  3/16

  e.  1/4

  e.  A piece of chromosomal material containing an active SRY gene is found attached to one of the X chromosomes.

 In humans, occasionally a baby is found that has the XX chromosomal karyotype but is phenotypically male. Which of the following statements explains some of these cases?

  a.  A mutation has occurred in the SRY gene, making it inactive.

  b.  The ratio of number of X chromosomes to number of sets of chromosomes is incorrect.

  c.  A small piece of autosomal chromosome 15 is missing but is too small to be detected.

  d.  An extra pierce of autosomal chromosome 15 is probably present in the genome but is too small to be detected.

  e.  A piece of chromosomal material containing an active SRY gene is found attached to one of the X chromosomes.

a. 50%

In Mendel's peas, yellow seeds are dominant to green. A pure-breeding yellow plant is crossed with a pure-breeding green plant. All of the offspring are yellow. If one of these yellow offspring is crossed with a green plant, what will be the expected proportion of plants with green seeds in the next generation?

a. 50%

b. 75%

c. 25%

d. 0%

e. 100%

b. 1/4

Two gene loci, A and B, assort independently, and alleles A and B are dominant over alleles a and b. What is the probability of producing an AB gamete from an AaBb individual?

  a.  9/16

  b.  1/4

  c.  1 (100%)

  d.  1/2

  e.  1/16

d. evolution.

A change in allele frequency within a population over time leads to

a. a genotype.

b. a phenotype.

c. mutations.

d. evolution.

e. a genome.

d. recombination

What process produces genetic variation through the creation of new combinations of alleles on a chromatid?

a. chromosome condensation

b. fertilization

c. mitosis

d. recombination

e. cytokinesis

e. It is X linked and recessive.

You discover a new mutation in Drosophila that causes an abnormal wing shape. When a male fly with this mutation is crossed to a homozygous normal female, the F1 are all wild-type phenotypically. The F2 flies consist of 1/2 phenotypically normal females, 1/4 phenotypically normal males, and 1/4 males with abnormal wings. What is the MOST likely explanation for the new mutant allele?

  a.  It is X linked and dominant.

  b.  It is autosomal and recessive.

  c.  It is Y linked.

  d.  It is autosomal and dominant.

  e.  It is X linked and recessive.

c. are circular

Prokaryotic chromosomes do NOT have telomeres because they

a. do not go through DNA replication.

b. are in the cytoplasm.

c. are circular.

d. do not go through mitosis.

e. have no centromeres.

e. 1/2

James is a 42-year-old man with hemophilia, a sex-linked recessive condition. His daughter, Susan, who has normal blood clotting, is married to Fred, who also has hemophilia. Susan and Fred are expecting their first child, and an ultrasound shows that the fetus is male. What is the approximate probability that their new son will have hemophilia?

a. 1/4

b. 3/4

c. 1

d. 2/3

e. 1/2

b. Dominance describes a relationship between alleles, not traits.

Select the answer that best describes the conceptual error contained in the following misconception: "Brown eyes are dominant over blue eyes."

a. Blue eyes are actually dominant over brown eyes.

b. Dominance describes a relationship between alleles, not traits.

c. Brown eyes and blue eyes are determined by different genes.

d. Brown eyes and blue eyes are codominant.

e. Eye color is not determined by genes.

e. 2

A male has Klinefelter syndrome with the chromosome pattern of XXXY. How many Barr bodies should be found in the nuclei of cells of this individual?

a. 3

b. 4

c. 0

d. 1

e. 2

a. alleles.

30. Genes come in different versions called

a. alleles.

b. genomes.

c. loci.

d. chromosomes.

e. genotypes.

b. many turtles and alligators

In which of the following organisms is gender/sex determined by the temperature during embryonic development?

a. fruit flies

b. many turtles and alligators

c. many snakes and birds

d. humans

e. mice

d. nitrogenous base and sugar

Which of the following pairs is a part of a single nucleotide?

a. guanine and cytosine, two nitrogenous bases

b. amino acid and nitrogenous base

c. sugar and amino acid

d. nitrogenous base and sugar

d. mutations.

Permanent, heritable changes in genetic information (DNA) are called

a. evolution.

b. SNP.

c. alleles.

d. mutations.

e. defects.

b. A, B, AB, O

A mother with blood type A has a child with blood type A. Give all possible blood types for the father of this child.

a. B, AB

b. A, B, AB, O

c. A, AB

d. A, B, O

e. O

a. 1/8

A eukaryotic diploid cell from an organism with the XX–XO sex determination system has two pairs of autosomes and one X chromosome, shown here.   What is the probability of a gamete from this individual that has the following genotype: alleles A and b, chromosome X?

  a.  1/8

  b.  1/4

  c.  1/16

  d.  1/2

  e.  1/6