Exam 3 Practice Problems

Which structural component of a eukaryotic chromosome is the attachment point for spindle microtubules during M-phase?

a. the centromere

b. sister chromatids

c. the origin of replication

d. the telomere

a. the centromere

Most body (nonreproductive) cells of humans and other multicellular eukaryotes have two sets of each chromosome. Such cells are ______ and the matching pair of chromosomes are called _________.

a. diploid; homologous chromosomes

b. haploid; homologous chromosomes

c. diploid; sister chromatids

d. tetraploid; sister chromatids

a. diploid; homologous

Sister chromatids separate and move toward opposite poles during which phase of mitosis?

a. prophase

b. pro-metaphase

c. metaphase

d. anaphase

e. telophase

d. anaphase

Meiosis I is called the ___________ division and meiosis II is called the __________ division.

a. reduction; equational

b. interphase; prophase

c. equational; reduction

d. mitotic; interphase

e. slow; rapid

a. reduction; equational

All of the following make meiosis different from mitosis, EXCEPT:

a. meiosis comprises two divisions.

b. chromosome number is reduced by half in meiosis.

c. resulting cells from meiosis are genetically different from the parent cell.

d. meiosis lacks preceding S and G2 phases.

e. pairing of homologous chromosomes usually only occurs in meiosis.

d. meiosis lacks preceding S and G2 phases.

Which of the following events of meiosis creates genetic variation among the gametes?

a. crossing over

b. random separation of maternal and paternal chromosomes

c. distribution of differing numbers of chromosomes to daughter cells

d. both a and b

e. all of the above

d. both a and b

A diploid somatic cell from a rat has a total of 42 chromosomes (2n = 42).

What is the total number of telomeres in a rat cell in G2?

a. 21

b. 42

c. 84

d. 126

e. 168

e. 168

What is the total number of chromosomes present in the cell during metaphase I of meiosis?

a. 21

b. 42

c. 84

d. 126

e. 168

b. 42

What is the total number of chromosomes in an egg cell of the rat?

a. 21

b. 40

c. 41

d. 42

e. 84

a. 21

Suppose that a diploid cell contains 10 chromosomes (2n = 10). How many different combinations in the gametes are possible?

a. 64

b. 5

c. 10

d. 20

e. 32

e. 32

According to Mendel's Second Law, when the different alleles for one trait separate into gametes, their separation:

a. is dependent upon how different alleles for other traits separate.

b. is independent of how different alleles for other traits separate.

c. occurs so as to prevent recessive alleles of two different genes from occupying the same gamete.

d. occurs so that recessive alleles of different genes always occupy the same gamete.

b. is independent of how different alleles for other traits separate.

A tall, purple flower plant with genotype Tt Pp is crossed with a tall, white flower plant of genotype Tt pp. What is the probability of obtaining progeny with genotype TTpp?

a. 1/8

b. 1/4

c. 1/2

d. 2/3

e. 3/4

a. 1/8

For the parent plants described in the previous question, what is the probability of obtaining offspring that are short and have purple flowers?

a. 0

b. 1/8

c. 1/4

d. 1/3

e. 1/2

b. 1/8

In a cross between AaBbCc and AaBbcc, what proportion of the offspring would be expected to be AaB_cc? (B_ means BB or Bb.)

a. 3/64

b. 3/32

c. 3/16

d. 3/8

e. 3/4

c. 3/16

A particular trait of diploid is determined by a single gene. If there are six possible alleles, then how many different possible genotypes are there?

a. 6

b. 12

c. 21

d. 36

e. 42

c. 21

A child who is blood type A has a mother who is blood type B. In a paternity suit a man is accused of being the father. He has blood type AB. Is he the father?

a. Yes

b. No

c. He cannot be excluded as the father.

c. He cannot be excluded as the father.

The difference between dominance and epistasis is that:

a. dominance masks genes at different loci.

b. epistasis masks genes at the same loci.

c. epistasis masks genes at different loci.

d. all of the above.

e. Dominance and epistasis are the same.

c. epistasis masks genes at different loci.

4. Interactions among the human ABO blood group alleles involve _______ and ________.

a. co-dominance; complete dominance

b. codominance; incomplete dominance

c. complete dominance; incomplete dominance

d. epistasis; complementation

e. continuous variation; environmental variation

a. co-dominance; complete dominance

In humans, blood types A and B are codominant to each other and each is dominant to O. What blood types are possible among the offspring of a couple of blood types AB and A?

a. A, B, AB, and O

b. A, B, and AB only

c. A and B only

d. A, B, and O only

e. A and AB only

b. A, B, and AB only

What will be the phenotype(s) of the F1 offspring of a true-breeding "fabulous" father and a true-breeding "plain" mother (aabb)?

a. all "plain"

b. all "smashing"

c. all "fabulous"

d. plain" females and "fabulous" males

e. "fabulous" females and "smashing" males

c. all "fabulous"

What will be the expected ratio of the F2 offspring of the F1 generation?

a. 9 "fabulous":7 "plain"

b. 13 "fabulous":3 "plain"

c. 9 "fabulous":3 "smashing":4 "plain"

d. 12 "plain":3 "fabulous":1 "smashing"

e. 15 "fabulous":1 "smashing"

c. 9 "fabulous":3 "smashing":4 "plain"

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. Upon close examination of the coats, each hair of a gray animal is gray. What is the mode of inheritance?

a. one gene pair with black dominant to white

b. one gene pair with codominance

c. one gene pair with incomplete dominance

d. two gene pairs with recessive epistasis

c. one gene pair with incomplete dominance

Why was the pea plant an ideal plant for Mendel to use?

a. It produces few progeny.

b. It has some traits, which are easy to be observed.

c. It requires cross-fertilization; there is no self-fertilization.

d. It requires several seasons to complete a generation.

e. There were only a few pure varieties available.

b. It has some traits, which are easy to be observed.

Mendel determined that for a given character, such as pea seed shape, an individual has two factors and that these can exist in two forms (R or r). Today we would describe R and r as being:

a. different genes of the seed shape locus.

b. different loci of the seed shape gene.

c. different alleles of the seed shape locus.

d. different genotypes of the seed shape character.

e. different traits of the seed shape character.

c. different alleles of the seed shape locus.

In Mendel's pea plants, how did he know that each F1 generation contained two alleles encoding different characteristics?

a. The F1 generation had a blended phenotype of the two parental phenotypes.

b. Both parental phenotypes reappeared in the F2 generation.

c. Each F1 plant had a different phenotype.

d. The F1 plants did not have two alleles.

e. None of the above.

b. Both parental phenotypes reappeared in the F2 generation.

An organism has the genotype Rr and the phenotype R. This is known as the concept of :

a. segregation.

b. dominance.

c. recessive.

d. Mendel.

e. hybridization.

b. dominance.

If an allele for tall (T) is dominant to an allele for short (t), what proportion of the progeny will be short in the following cross: Tt × Tt?

a. 0/4

b. 1/4

c. 2/4

d. 3/4

e. 4/4

b. 1/4

Individual #1 with phenotype "A" is test-crossed and half of the offspring produced have phenotype "A" and half have phenotype "a." What are the genotypes of the individuals that were crossed?

a. AA and aa

b. Aa and aa

c. Aa and Aa

d. AA and Aa

b. Aa and aa

Which of the following was not one of Mendel's conclusions based on his monohybrid crosses?

a. Genes are carried on chromosomes.

b. Genes exist in pairs.

c. Members of a gene pair segregate equally into gametes.

d. Genes behave as genetic factors during inheritance.

e. One member of a gene pair can mask the expression of the other member.

a. Genes are carried on chromosomes.

An animal's black coat color (B) is dominant to brown (b). If a black individual is mated with a brown one and the offspring are 3 black and 2 brown puppies. What can you conclude about the genotype of the black parent?

a. The genotype must be BB.

b. The genotype must be bb.

c. The genotype must be Bb.

d. The genotype could be either BB or Bb.

e. The genotype cannot be determined from this data.

c. The genotype must be Bb.

In Mendel's peas, purple flower color is dominant to white. From which of the following phenotype or descriptions you can NOT infer the genotype for the locus completely?

a. purple

b. white

c. pure-breeding purple

d. heterozygous

e. More than one of the above.

a. purple

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. 0%

b. 25%

c. 50%

d. 75%

e. 100%

c. 50%