Question 1

Polyploidy refers to the:

Accepted Answer

Polyploidy is the condition in which an organism has more than two complete sets of chromosomes, resulting from the gain of a complete set of chromosomes.

Question 2

Which of the following is true of Mendel's second law but not his first law?

Accepted Answer

Mendel's second law, the Law of Independent Assortment, states that alleles of different genes assort independently of one another during gamete formation. This is different from his first law, the Law of Segregation, which states that the two alleles of a gene separate during gamete formation.

Question 3

Suppose that a plant has two genes that are linked, with Ab on one homolog of a homologous pair of chromosomes and aB on the other homolog.What gametes could the plant produce if crossing-over occurred between these genes during meiosis?

Accepted Answer

Crossing-over between linked genes can result in recombinant gametes, so all four combinations (Ab, aB, AB, and ab) are possible.

Question 4

Consider the two traits, seed shape and seed color.R represents the allele for round seeds, r the allele for wrinkled seeds, Y the allele for yellow seeds, and y the allele for green seeds.What phenotypic ratio would you expect in the offspring of a cross between a plant with wrinkled green seeds and a plant heterozygous for both traits?

Accepted Answer

The cross involves a plant with genotype "rryy" (wrinkled green) and a plant with genotype "RrYy" (heterozygous for both traits). The expected phenotypic ratio for a dihybrid cross of this nature is 1:1:1:1 for the phenotypes round yellow, round green, wrinkled yellow, and wrinkled green.

Question 5

Cytoplasmic inheritance in plants involves genes present in the:

Accepted Answer

Cytoplasmic inheritance in plants involves genes present in both mitochondria and plastids, as these organelles contain their own DNA and are inherited maternally.

Question 6

Consider the two traits, seed shape and seed color.R represents the allele for round seeds, r the allele for wrinkled seeds, Y the allele for yellow seeds, and y the allele for green seeds.Which of the following indicates a cross between a plant heterozygous for both traits and a plant homozygous recessive for both traits?

Accepted Answer

A heterozygous plant for both traits would have the genotype RrYy, and a homozygous recessive plant for both traits would have the genotype rryy. Therefore, the cross is RrYy × rryy.

Question 7

In peas, the dominant alleles A and B must be present for purple flower pigment to be produced; otherwise the flowers are white.What offspring would you expect from a cross between plants of genotypes Aabb and aaBb?

Accepted Answer

The cross Aabb x aaBb results in offspring with genotypes AaBb, Aabb, aaBb, and aabb. Only AaBb will have both dominant alleles A and B for purple flowers, resulting in a 1:3 ratio of purple to white flowers.

Question 8

Which of the following statements about transposons is FALSE?

Accepted Answer

Transposons are found in both prokaryotic and eukaryotic organisms, not just in bacteria.

Question 9

In ______, a single gene has many different effects on the phenotype.

Accepted Answer

Pleiotropy occurs when one gene influences multiple phenotypic traits.

Question 10

In peas, tall stem length is dominant over short length.What genotypic ratio would you expect in the offspring of a cross between a heterozygous tall plant and a homozygous short plant?

Accepted Answer

A heterozygous tall plant (Tt) crossed with a homozygous short plant (tt) will produce offspring with a genotypic ratio of 1 heterozygous tall (Tt) to 1 homozygous short (tt).

Question 11

When a trait exhibits continuous variation in a population of organisms, it most likely is due to:

Accepted Answer

Continuous variation in a trait is typically due to the interaction of multiple genes, each contributing to the phenotype, known as polygenic inheritance.

Question 12

In snapdragons, a cross between a red-flowered plant and a white-flowered plant produces a plant with pink flowers.What offspring would you expect from a cross between two pink-flowered plants?

Accepted Answer

This is an example of incomplete dominance, where the heterozygous condition results in a blend of the two parental traits. Crossing two pink (heterozygous) plants results in a 1:2:1 ratio of red:pink:white.

Question 13

The exchange of segments between nonhomologous chromosomes is called a(n):

Accepted Answer

Translocation is the exchange of segments between nonhomologous chromosomes.

Question 14

Which of the following statements concerning mutations is FALSE?

Accepted Answer

The mutation rate in eukaryotes is generally much lower than one mutant gene per 2000 cell divisions.

Question 15

Which of the following is NOT a possible cause of maternal inheritance?

Accepted Answer

Maternal inheritance typically involves the transmission of organelles like plastids and mitochondria from the mother. If only plastids are transmitted into the egg, it contradicts the concept of maternal inheritance, which involves both organelles.

Question 16

When the phenotype of a heterozygote is intermediate between the phenotypes of its homozygous parents, the condition is known as:

Accepted Answer

Incomplete dominance occurs when the phenotype of a heterozygote is intermediate between the phenotypes of its homozygous parents, as neither allele is completely dominant over the other.

Question 17

A population of organisms that has four alleles for a given gene is said to have:

Accepted Answer

A population with four alleles for a given gene exhibits multiple alleles, which refers to the presence of more than two alleles for a genetic locus within a population.

Question 18

If W represents the allele for purple flower color, and w represents the allele for white flower color, what phenotypic ratio would you expect for the offspring of a testcross?

Accepted Answer

The answer of If W represents the allele for purple...

Question 19

In peas, green pod color is dominant over yellow pod color.If a plant heterozygous for pod color is crossed with a plant homozygous recessive for pod color, what phenotypes would you expect in the offspring?

Accepted Answer

A heterozygous plant (Gg) crossed with a homozygous recessive plant (gg) will produce offspring with a 1:1 ratio of green (Gg) to yellow (gg) pods.

Question 20

If two genes are linked, then by definition they:

Accepted Answer

Linked genes are located on the same chromosome and tend to be inherited together because they do not assort independently.

Quiz 8: Sexual Reproduction and Heredity