Question 1

If the cross BbDD x bbDd is made, which of the following would NOT be represented in the offspring?

Accepted Answer

The answer of If the cross BbDD x bbDd is...

Question 2

The British biologists who first reported linkage in sweet peas were

Accepted Answer

The British biologists who first reported linkage in sweet peas were William Bateson and Reginald Punnett.

Question 3

Since Mendel's time, types of inheritance that don't follow Mendel's rules have been discovered.Which of the following situations is NOT an exception to Mendel's rules?

Accepted Answer

This situation, where an individual with a heterozygous phenotype for a trait is crossed with an individual with a homozygous recessive phenotype, follows Mendel's law of segregation and would produce a phenotypic ratio of 1:1. The other options (A, B, C, and E) describe exceptions to Mendelian inheritance.

Question 4

If red is dominant and yellow is recessive as a flower color in a certain species of plants, and if, in the same plants, long hairs are dominant and absence of hair is recessive, and a dihybrid cross involving homozygous parents is made, which of the following phenotypes would NOT appear in the F2 generation?

Accepted Answer

Orange, hairy phenotype would not appear because orange is not a possible phenotype in this genetic cross; the colors are red (dominant) and yellow (recessive).

Question 5

Which of the following is NOT known for the pioneer experiments and theories that led to the development of the science of genetics?

Accepted Answer

Linnaeus is known for creating the binomial naming system for organisms and is considered the father of modern taxonomy, but he did not contribute to the development of genetics.

Question 6

When Mendel crossed tall pea plants with short ones, all of the offspring were intermediate in height.

Accepted Answer

This statement is false. In Mendel's experiments, the offspring of a tall plant crossed with a short plant were not all intermediate in height. Instead, they tended to be predominantly tall, with a ratio of about 3:1 tall to short plants. This pattern of inheritance follows the principles of dominant and recessive traits, which Mendel discovered.

Question 7

In a cross between a long and a globe-shaped radish, the F₁ generation consisted of 247 oval-shaped radishes.The F₂ generation consisted of 62 long radishes, 127 oval radishes, and 59 globe-shaped radishes.Which of the following pertaining to this cross is true?

Accepted Answer

The answer of In a cross between a long and...

Question 8

In a variety of cornflowers in which blue flowers and dwarf plants are controlled by dominant genes carried on separate pairs of chromosomes, and white flowers and tall plants are their recessive counterparts, assume a cross has been made between a homozygous blue, dwarf plant and a homozygous white, tall plant.Which of the following would be represented in the F₁ generation?

Accepted Answer

The parental plants are homozygous blue dwarf (BBDD) and homozygous white tall (bbdd), respectively. Their offspring in the F1 generation would all be heterozygous for both traits, with genotype BbDd. When F1 individuals are self-crossed, the possible genotypes of the F₁ generation are: BBDD, BbDD, bbDD, BBDd, BbDd, bbDd, BbDD, Bbdd, and bbdd. However, because blue dwarf (BBDD) and white tall (bbdd) are the parent's phenotypes, respectively, the only ones that match that are BbDd, Bbdd, and BbDD. Therefore, the best choice is D, BbDd.

Question 9

Mendel discovered the rules of inheritance only after the discoveries of chromosomes and meiosis.

Accepted Answer

Mendel's laws of inheritance were discovered through experiments with pea plants in the mid-1800s, while the discoveries of chromosomes and meiosis didn't occur until the late 1800s and early 1900s.

Question 10

The most significant cause for exceptions to the Hardy-Weinberg law is

Accepted Answer

Selection is the most significant cause for exceptions to the Hardy-Weinberg law as it can favor certain alleles over others, leading to a change in allele frequencies in a population over time. This violates the assumption of random breeding and can result in deviations from the expected genotype frequencies. The other listed factors (protoplast fusion, polyploidy, proportion of dominant to recessive genes, and random breeding) can also lead to deviations from the law, but their impact is generally considered to be less significant than selection.

Question 11

If a pure breeding parent producing yellow seeds, the dominant phenotype, is crossed with a pure breeding parent producing green seeds, the recessive phenotype, the F1 generation will produce

Accepted Answer

In a cross between a pure breeding dominant phenotype (yellow seeds) and a pure breeding recessive phenotype (green seeds), all F1 offspring will express the dominant phenotype, resulting in 100% yellow seeds.

Question 12

Assume the same cross as in question 24.If the F2 generation involves thousands of individual plants that are carefully counted, and four different phenotypes in a ratio other than 9:3:3:1 are noted, which of the following would be suspected?

Accepted Answer

A ratio other than 9:3:3:1 suggests that the genes for the traits being studied are not assorting independently, which could be due to linkage, where the genes are physically located close together on the same chromosome and tend to be inherited together. In this case, crossing-over would not have occurred between the genes, leading to non-Mendelian inheritance ratios.

Question 13

Chromosomal mapping primarily involves

Accepted Answer

Chromosomal mapping involves analyzing the frequency of crossovers and recombination during meiosis in order to determine the relative positions of genes on a chromosome. Calculating crossover percentages is a key component of this process. The other options (A-D) are not directly involved in chromosomal mapping.

Question 14

Which of the following increases the probability of genes being inherited together?

Accepted Answer

Two genes that are physically close to each other on a chromosome are more likely to be inherited together during meiosis. This is because the likelihood of the chromosome breaking and separating the genes during crossing over is reduced.

Question 15

In sweet peas, purple flower color and oblong pollen grains are dominant, with the recessives being red flower color and spherical pollen grains.When a homozygous purple, oblong plant is crossed with a homozygous red, spherical plant, the F₁ generation consists entirely of purple, oblong plants.When an F₁ plant is crossed with a homozygous red, spherical plant, the offspring are produced in a ratio of 7 purple, oblong to 1 purple, spherical to 1 red, oblong to 7 red, spherical.Which of the following is the only plausible explanation for such results?

Accepted Answer

The results suggest that the purple and oblong traits are linked on one chromosome, while the red and spherical traits are linked on another chromosome. This is because the F₁ plant must have received both dominant traits on the same chromosome from the homozygous parent, resulting in a homozygous dominant plant, while the offspring from the second cross show a 9:7 ratio, which is indicative of two linked traits. Fertilizer, bad sex cells, and plant resentment are not plausible explanations for the results.

Question 16

Which is a heterozygous genotype for a given trait?

Accepted Answer

Heterozygous genotype means there are two different alleles for a particular gene. In option B, Yy represents a heterozygous genotype. The allele Y and y are different from each other. Option A (YY) represents a homozygous dominant genotype, option D (yy) represents homozygous recessive genotype, and option C (WX) represents a genotype not related to the trait in question.

Question 17

What is the correct genotype of a homozygous dihybrid individual having dominant phenotypes for both traits?

Accepted Answer

Homozygous individuals have two copies of the same allele for a given gene. Since this individual has dominant phenotypes for both traits, they must have two dominant alleles for each gene. The only option with two dominant alleles for each gene is TTXX.

Question 18

A single pair of genes controls red versus blue flower color in larkspurs, and red is dominant phenotype.Which of the following phenotypes should occur in the F₃ generation if the parental generation was pure breeding strains for red and blue phenotypes?

Accepted Answer

In the F1 generation, all offspring would be red (heterozygous). In the F2 generation, a 3:1 ratio of red to blue would appear. This ratio would continue in the F3 generation, resulting in both red and blue phenotypes.

Question 19

Assume the same cross as in question 29.How many different kinds of genotypes would occur in the F2 generation?

Accepted Answer

In a dihybrid cross, the F2 generation typically results in 9 different genotypes due to the combination of alleles from two heterozygous parents.

Question 20

Assume the same cross as in question 29.Which of the following phenotypic ratios would be represented in the F₂ generation?

Accepted Answer

The F₂ generation is the result of a dihybrid cross between and _{individuals. The expected phenotypic ratio for a dihybrid cross between two heterozygous individuals (}_{) is 9:3:3:1. Therefore, the answer is D.}

Quiz 13: Genetics