Question 1

You are given two populations of true-breeding tomato plants with two simple dominant/recessive traits that sort independently. Using the multiplication rule, how many different phenotypic combinations would you expect to see in the F₂ generation? In what phenotypic ratio?

Accepted Answer

The multiplication rule states that the probability of two independent events occurring together is the product of their individual probabilities. In this case, we have two independent traits, each with two possible alleles (dominant or recessive), so there are a total of 4 possible allele combinations.
To determine the number of phenotypic combinations, we must consider the possible combinations of these alleles. Using a Punnett square, we can see that these 4 allele combinations will result in 4 possible phenotypes: 
1) homozygous dominant for trait 1 and homozygous dominant for trait 2
2) homozygous dominant for trait 1 and heterozygous for trait 2
3) heterozygous for trait 1 and homozygous dominant for trait 2
4) heterozygous for both traits
Thus, there are 4 possible phenotypic combinations, which will occur in a ratio of 9:3:3:1 (as predicted by the dihybrid cross). Therefore, the best choice is C.

Question 2

Why was it important for Mendel to remove the anthers from pea plants in his experiments when crossing two different true-breeding pea plants?

Accepted Answer

By removing the anthers, Mendel prevented the pea plants from self-fertilizing and ensured that the only way for fertilization to occur was through cross-pollination with another true-breeding plant. This allowed him to accurately track the inheritance patterns of specific traits without the interference of unpredictable variations resulting from self-fertilization.

Question 3

One of Mendel's most important discoveries was:

Accepted Answer

Mendel observed that during the formation of gametes, the two alleles for a trait segregate from each other so that each gamete carries only one allele for each trait. This is known as the principle of segregation and is one of Mendel's most important discoveries. While dominance and reciprocal crosses are also important concepts in genetics, they were not Mendel's most significant contribution. Mutation, while relevant to genetics, was not a discovery made by Mendel.

Question 4

Which of the following statements is TRUE regarding Charles Darwin?

Accepted Answer

All of the statements are true regarding Charles Darwin. He did subscribe to the idea of blending inheritance, which did pose problems for his theory of natural selection because it could not explain how variations were preserved in populations. Despite this, he established the theory of natural selection as a mechanism for evolution. The concept of blending inheritance was indeed seen as a homogenizing force, which conflicted with the preservation of advantageous traits in his theory. Darwin struggled to reconcile blending inheritance with natural selection, a synthesis that was not achieved in his lifetime.

Question 5

What is an allele?

Accepted Answer

An allele is one of several different forms of a gene. Each individual organism inherits two alleles for each gene, one from each parent. These alleles can be the same or different, leading to variations in traits among individuals.

Question 6

Which of the following statements is TRUE regarding Mendel's work?

Accepted Answer

Mendel focused on seven easily observable traits in pea plants, such as seed shape and flower color, which allowed him to clearly distinguish between different generations and analyze inheritance patterns.

Question 7

According to the principle of segregation, a heterozygous plant with alleles Aa will produce:

Accepted Answer

The principle of segregation states that during gamete formation, the alleles for a gene separate so that each gamete carries only one allele for each gene. Therefore, a heterozygous plant (Aa) will produce gametes with the A allele and gametes with the a allele in a 1:1 ratio.

Question 8

If one of the traits Mendel studied was encoded by a single gene with three alleles that produced different phenotypes, what would he have observed if he crossed all possible pairs of the three true-breeding lines in the F₁ and F₂ generations?

Accepted Answer

The answer of If one of the traits Mendel studied...

Question 9

A high school student wants to repeat Mendel's classic experiments for her science fair. To stay true to Mendel's work, what must the student do?

Accepted Answer

Mendel's experiments involved removing the male organs to prevent self-pollination and hand-pollinating to control the traits being studied, while keeping careful records of the traits in the parent plants.

Question 10

True-breeding plants are typically heterozygous for most genes.

Accepted Answer

True-breeding plants are homozygous for most genes, meaning they have two copies of the same allele for a particular trait.

Question 11

Imagine that a rancher has a herd of cattle with brown hides and short horns. All of his cattle are also relatively short in stature. If all of these traits were true-breeding, what could you say about the progeny of these cattle?

Accepted Answer

Since all of the traits are true-breeding, this means that the offspring will have the same traits as the parents. Therefore, the progeny of these cattle will also have brown hides, short horns, and be relatively short in stature.

Question 12

Which of the following genotypes would result in a true-breeding stock?

Accepted Answer

True-breeding stock refers to a group of organisms that, through multiple generations of breeding, consistently display a particular trait. This can only occur if the genotype remains constant through multiple generations. The only genotype that guarantees this is homozygous (AA or aa), as heterozygous (Aa) genotypes can produce different gametes and offspring, leading to variation in the trait. Therefore, either AA or aa (homozygous) but not Aa (heterozygous) would result in a true-breeding stock. Choice E accounts for this by including both homozygous genotypes but excluding the heterozygous genotype.

Question 13

In Mendel's experiments, his parental pea plants are referred to as the F₁ generation, and their progeny are referred to as the P₁ generation.

Accepted Answer

In Mendel's experiments, the parental generation is referred to as the P generation, their progeny as the F1 generation, and the next generation as the F2 generation.

Question 14

What made the plant hybridization studies performed by Mendel more successful than plant hybridization studies performed by others?

Accepted Answer

Mendel's use of statistical analysis allowed him to recognize patterns of inheritance and make predictions about future generations of plants. This made his experiments more rigorous and allowed him to confidently draw conclusions about the mechanisms of genetic inheritance.

Question 15

Which of the following was NOT a trait that Mendel studied in pea plants?

Accepted Answer

Mendel did not study leaf size in pea plants. He mainly focused on traits such as seed color, flower color, plant height, and seed shape or texture.

Question 16

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?

Accepted Answer

The first generation (F1) from a cross between true-breeding black (BB) and white (bb) rabbits would all be heterozygous (Bb), as each parent contributes one allele. When these F1 individuals (Bb) are crossed among themselves, the expected genotypic ratio in the F2 generation is 1 BB : 2 Bb : 1 bb. However, the question specifies an F₁ generation, which seems to be a typographical error or a misunderstanding. Assuming the question intends to ask about the F1 generation from the described cross, all offspring would be heterozygous (Bb), as they inherit one B allele from the black rabbit parent and one b allele from the white rabbit parent, resulting in 0 BB, 0 bb, and 16 Bb.

Question 17

A true-breeding black rabbit is crossed with a true-breeding white rabbit to produce an F₁ generation of 15 individuals. If the black color trait is dominant, which of the following represents the expected phenotype of an F₁ generation cross?

Accepted Answer

Since black is the dominant trait and both parents are true-breeding (homozygous) for their respective colors, all offspring in the F1 generation would express the dominant black phenotype.

Question 18

Which of the following statements is TRUE regarding the yellow-seed pea plants of Mendel's work?

Accepted Answer

The yellow seed color in Mendel's pea plants is due to the presence of an enzyme that breaks down chlorophyll, not because they produce more chlorophyll or because it's a recessive trait. The statement about specific generations is not relevant to the genetic trait of seed color.

Question 19

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.

Accepted Answer

Huntington's disease is caused by a dominant allele, which means that if an individual inherits even one copy of the allele, they will develop the disease. This is why Huntington's disease is considered a dominant trait.

Question 20

Consider Mendel's experiments involving the trait of round versus wrinkled peas. In some experiments, Mendel removed the anthers of the flowers from a plant that was true-breeding for round peas and applied pollen from the anthers of a plant that was true-breeding for wrinkled peas. What would have happened if Mendel missed some anthers that he was trying to remove from the true-breeding round pea plants, and then counted the peas produced by a plant that bore a mix of round and wrinkled pollen? Indicate which of the following must be TRUE.

Accepted Answer

If Mendel missed some anthers, the F1 generation would still show a single phenotype (round peas) because round is dominant over wrinkled.

Quiz 16: Mendelian Inheritance

You are given two populations of true-breeding tomato plants with two simple dominant/recessive traits that sort independently. Using the multiplication rule, how many different phenotypic combinations would you expect to see in the F2 generation? In what phenotypic ratio?