Q: A geneticist performs a cross between PpYyRr and Ppyyrr. What is the probability that an offspring will be pp yy rr?

$$\frac{1}{4} \times \frac{1}{2} \times \frac{1}{2} = \frac{1}{16}$$

Question 1

Which of the following best describes a true-breeding organism?

Accepted Answer

An organism that, when crossed with another of the same phenotype, produces offspring with only that phenotype.

Question 2

In a monohybrid cross between two heterozygous tall pea plants (Tt x Tt), where tall (T) is dominant to short (t), what is the expected phenotypic ratio of the offspring?

Accepted Answer

$$3$$ tall : $$1$$ short

Question 3

Which statement correctly distinguishes between genotype and phenotype?

Accepted Answer

Genotype refers to the genetic makeup, while phenotype refers to the observable traits.

Question 4

A zygote formed after fertilization contains how many copies of each gene, and where do these copies originate?

Accepted Answer

Two copies; one from the sperm and one from the egg.

Question 5

Which of the following best describes complete dominance?

Accepted Answer

The dominant allele completely masks the presence of the recessive allele in a heterozygote.

Question 6

If a genetic disorder is caused by a recessive allele, what is the probability that two heterozygous parents (Rr x Rr) will have an affected child?

Accepted Answer

$$\frac{1}{4}$$

Question 7

Which of the following is an example of a homozygous genotype?

Accepted Answer

AA

Question 8

A geneticist wants to predict the frequency of a child being homozygous recessive for three independent traits (each parent is heterozygous for all traits). What is the probability the child will be homozygous recessive for all three traits?

Accepted Answer

$$\left(\frac{1}{4}\$$right)^3$$ = \frac{1}{64}$$

Question 9

Which cross would produce only heterozygous offspring?

Accepted Answer

AA x aa

Question 10

In a Punnett square for a cross between Aa (black hair) and aa (red hair), what is the expected genotypic ratio?

Accepted Answer

$$1 Aa$$ : $$1 aa$$

Question 11

Which of the following best describes hybridization in genetics?

Accepted Answer

The combination of different alleles from two parents.

Question 12

If a child inherits the genotype Bb for sickle cell (B = normal, b = sickle cell), what is the phenotype?

Accepted Answer

Normal

Question 13

Which of the following is NOT a correct pairing of terms?

Accepted Answer

Heterozygous – two copies of the same allele

Question 14

A couple, both carriers for cystic fibrosis (a recessive disorder), want to know the probability that two of their three children will have the disorder. Which rule should they use to calculate this probability?

Accepted Answer

The rule of multiplication

Question 15

If an individual has the genotype Ss for height (S = tall, s = short), what is the phenotype if S is completely dominant?

Accepted Answer

Tall

Question 16

Which of the following crosses would result in a 1:1 phenotypic ratio if the dominant allele is completely dominant?

Accepted Answer

Heterozygous x homozygous recessive

Question 17

A geneticist performs a cross between PpYyRr and Ppyyrr. What is the probability that an offspring will be pp yy rr?

Accepted Answer

$$\frac{1}{4} 	imes \frac{1}{2} 	imes \frac{1}{2} = \frac{1}{16}$$

Question 18

Which of the following best explains why a recessive trait may skip generations in a family?

Accepted Answer

The trait is only expressed when an individual has two copies of the recessive allele.

Question 19

If a parent with genotype Bb (normal) and a parent with genotype bb (sickle cell) have children, what is the probability that a child will have sickle cell?

Accepted Answer

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

Question 20

Which of the following scenarios demonstrates the rule of multiplication in genetics?

Accepted Answer

Calculating the probability of inheriting two independent recessive traits by multiplying their individual probabilities.

Mendelian Genetics: Key Concepts and Applications

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