Question 1

Which of the following best describes Mendel's Law of Segregation?

Accepted Answer

Alleles for a trait separate during gamete formation, so each gamete carries only one allele for each gene.

Question 2

A plant with genotype $$PpYyRr is $$crossed with another $$PpYyRr$$ plant. What is the probability that an offspring will have at least two recessive traits (i.e., at least two of the traits are homozygous recessive)?

Accepted Answer

$$\frac{3}{8}$$

Question 3

Which scenario is an example of incomplete dominance?

Accepted Answer

A red-flowered plant crossed with a white-flowered plant produces all pink-flowered offspring.

Question 4

In a dihybrid cross between two heterozygotes ($$YyRr 	imes YyRr$$), what is the expected phenotypic ratio in the F2 generation if the genes assort independently?

Accepted Answer

9:3:3:1

Question 5

Which of the following best explains why linked genes do not always follow Mendel's Law of Independent Assortment?

Accepted Answer

Linked genes are located close together on the same chromosome and tend to be inherited together unless crossing over occurs.

Question 6

A woman is homozygous for a mutant allele of the $$BRCA1$$ gene, which has 65% penetrance for breast or ovarian cancer. What does this mean?

Accepted Answer

She has a 65% chance of developing breast or ovarian cancer during her lifetime.

Question 7

Which of the following is an example of pleiotropy?

Accepted Answer

A single gene mutation causes both light sensitivity and lack of melanin in the skin, eyes, and hair.

Question 8

In Labrador retrievers, the $$E$$ gene allows pigment deposition in hair, while the $$B$$ gene determines black or brown pigment. If a dog is $$eeBB$$, what will its coat color be?

Accepted Answer

Yellow

Question 9

Which of the following best describes the concept of expressivity?

Accepted Answer

The degree to which a genotype is expressed in the phenotype among individuals with the same genotype.

Question 10

A cross between a homozygous dominant ($$RR) $$and a homozygous recessive ($$rr) $$pea plant produces all $$Rr$$ offspring. If two $$Rr$$ plants are crossed, what is the expected genotypic ratio in the F2 generation?

Accepted Answer

1 $$RR$$ : 2 $$Rr$$ : 1 $$rr$$

Question 11

Which of the following is an example of a multifactorial trait?

Accepted Answer

Hydrangea flower color, which depends on both genotype and soil pH.

Question 12

If two genes are located very far apart on the same chromosome, what is the expected proportion of recombinant gametes due to crossing over?

Accepted Answer

50%

Question 13

Which probability rule would you use to determine the chance of two independent genetic events both occurring?

Accepted Answer

Multiplication rule

Question 14

A person with genotype $$I^A I^B$$ for the ABO blood group will have which blood type?

Accepted Answer

AB

Question 15

Which of the following best describes the difference between penetrance and expressivity?

Accepted Answer

Penetrance is the proportion of individuals with a genotype who show the phenotype, while expressivity is the degree to which the phenotype is expressed.

Question 16

Which of the following is an example of codominance?

Accepted Answer

A person with genotype $$I^A I^B$$ expresses both A and B antigens on red blood cells.

Question 17

Which of the following crosses would you use to determine the genotype of an individual with a dominant phenotype?

Accepted Answer

A test cross with a homozygous recessive individual

Question 18

Which of the following best explains why identical twins can have different phenotypes despite having the same genotype?

Accepted Answer

Environmental factors can influence gene expression, leading to phenotypic differences.

Question 19

In a population, a gene has four alleles that determine rabbit fur color. What is this an example of?

Accepted Answer

Multiple alleles

Question 20

Which of the following is true about epistasis?

Accepted Answer

The phenotypic expression of one gene is affected by the genotype at a second gene.

Mendelian Genetics: Principles, Probability, and Exceptions

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