Q: If a genetic counselor uses the multiplication rule to determine the probability of a child inheriting two independent recessive traits, which calculation is correct?

$$\frac{1}{4} \times \frac{1}{4} = \frac{1}{16}$$

Question 1

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

Accepted Answer

Two alleles for a heritable character separate during gamete formation and end up in different gametes.

Question 2

A pea plant with genotype $$Pp is $$crossed with a pea plant with genotype $$pp. $$What is the expected ratio of purple to white flowers in the offspring?

Accepted Answer

$$1:1 ($$purple:white)

Question 3

Which statement about dominant alleles is correct?

Accepted Answer

Dominant alleles mask the effect of recessive alleles in heterozygotes.

Question 4

In a dihybrid cross between two $$YyRr$$ pea plants, what is the probability of obtaining an offspring with genotype $$YYRR$$?

Accepted Answer

$$\frac{1}{16}$$

Question 5

Which of the following is an example of pleiotropy?

Accepted Answer

A single gene causing multiple symptoms in cystic fibrosis.

Question 6

A testcross is performed between a pea plant with purple flowers of unknown genotype and a white-flowered plant ($$pp). If $$half the offspring are purple and half are white, what is the genotype of the purple-flowered parent?

Accepted Answer

$$Pp$$

Question 7

Which rule is used to calculate the probability that two independent events will both occur?

Accepted Answer

Multiplication rule

Question 8

In Labrador retrievers, coat color is determined by two genes. If two $$BbEe$$ dogs are crossed, what is the expected ratio of black:chocolate:yellow puppies?

Accepted Answer

$$9:3:4$$

Question 9

Which of the following best explains why polydactyly, a dominant trait, is rare in the population?

Accepted Answer

Dominant alleles are not necessarily more common than recessive alleles; frequency depends on other factors.

Question 10

A couple, both of whom have a sibling affected by a rare recessive genetic disorder, want to know the probability that their child will have the disorder. Assuming neither parent is affected, what is the probability?

Accepted Answer

$$\frac{1}{9}$$

Question 11

Which inheritance pattern is illustrated by the ABO blood group system in humans?

Accepted Answer

Multiple alleles and codominance

Question 12

Which of the following is true about polygenic inheritance?

Accepted Answer

It produces quantitative variation along a continuum.

Question 13

A heterozygous plant ($$Rr) is $$self-pollinated. What is the probability that an offspring will be heterozygous?

Accepted Answer

$$\frac{1}{2}$$

Question 14

Which of the following best describes the difference between phenotype and genotype?

Accepted Answer

Phenotype is the physical appearance; genotype is the genetic makeup.

Question 15

Which scenario is an example of multifactorial inheritance?

Accepted Answer

Skin color influenced by multiple genes and environmental exposure to sunlight.

Question 16

If a genetic counselor uses the multiplication rule to determine the probability of a child inheriting two independent recessive traits, which calculation is correct?

Accepted Answer

$$\frac{1}{4} 	imes \frac{1}{4} = \frac{1}{16}$$

Question 17

Which of the following is NOT a reason why Mendel chose pea plants for his experiments?

Accepted Answer

Peas have a long generation time.

Question 18

Which genetic disorder is caused by a dominant allele and has late onset symptoms?

Accepted Answer

Huntington's disease

Question 19

Which of the following best describes codominance?

Accepted Answer

Both alleles in a heterozygote are fully expressed in the phenotype.

Question 20

Which of the following is a correct application of the addition rule in genetics?

Accepted Answer

Calculating the probability of an offspring being either homozygous dominant or heterozygous.

Mendel and the Gene Idea: Principles of Inheritance

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