Q: Which formula would you use to calculate the probability of two independent genetic events both occurring?

$$P(A \cap B) = P(A) \times P(B)$$

Question 1

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

Accepted Answer

Alleles for each gene segregate so that each gamete receives only one allele.

Question 2

A couple are both carriers for cystic fibrosis (genotype Cc). What is the probability that their child will have cystic fibrosis?

Accepted Answer

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

Question 3

Which genetic mechanism explains why alleles for different genes located on separate chromosomes are inherited independently?

Accepted Answer

Random orientation of homologous chromosomes during Metaphase I of meiosis

Question 4

In a dihybrid cross between two heterozygotes (AaBb x AaBb), what is the expected phenotypic ratio if the genes assort independently?

Accepted Answer

$$9:3:3:1$$

Question 5

Which of the following is an example of incomplete dominance?

Accepted Answer

A snapdragon plant with red flowers crossed with a white flower producing pink offspring

Question 6

If a parent with genotype AaBbCC mates with a parent with genotype aaBbCc, what is the probability that their child will have genotype aaBbCC? (Assume independent assortment.)

Accepted Answer

$$\frac{1}{8}$$

Question 7

Which statement best explains the evolutionary benefit of the cystic fibrosis allele in regions affected by cholera?

Accepted Answer

Carriers of the CF allele (heterozygotes) have partial resistance to cholera toxin-induced dehydration.

Question 8

Which formula would you use to calculate the probability of two independent genetic events both occurring?

Accepted Answer

$$P(A \cap B) = P(A) 	imes P(B)$$

Question 9

A pedigree shows a disease affecting only males and skipping generations. Which inheritance pattern is most likely?

Accepted Answer

X-linked recessive

Question 10

Which of the following best describes codominance?

Accepted Answer

Both alleles are fully expressed in the phenotype.

Question 11

In Labrador retrievers, coat color is determined by two genes: B (black/brown) and E (color/no color). What is the expected phenotypic ratio when crossing BbEe x BbEe?

Accepted Answer

$$9$$ black : $$3$$ brown : $$4$$ yellow

Question 12

Which of the following is a real-world example of a polygenic trait?

Accepted Answer

Height

Question 13

A genetic counselor is working with a couple, both of whom have a sibling with a recessive disease but are unaffected. What is the probability that both are carriers?

Accepted Answer

$$\frac{2}{3}$$

Question 14

Which process during meiosis increases genetic diversity by creating new combinations of alleles on the same chromosome?

Accepted Answer

Crossing over during Prophase I

Question 15

If a person with genotype IAIB (AB blood type) has children with a person with genotype ii (O blood type), what are the possible blood types of their children?

Accepted Answer

A and B only

Question 16

Which of the following is NOT a feature of Mendel’s experimental approach?

Accepted Answer

Studying only polygenic traits

Question 17

Which genetic principle explains why the probability of a child inheriting a particular allele from each parent is independent of previous children’s outcomes?

Accepted Answer

Independent events in probability

Question 18

Which of the following best explains why achondroplasia, a dominant disorder, is rare in the population?

Accepted Answer

Homozygosity for the dominant allele is lethal.

Question 19

Which scenario is an example of epistasis?

Accepted Answer

Yellow coat color in Labradors resulting from the ee genotype masking the B gene

Question 20

How many possible combinations of chromosomes can be produced in human gametes due to independent assortment? (Humans have $$n=23$$ pairs of chromosomes.)

Accepted Answer

$$2^{23}$$

Genetics Part 2 Study Guide: MCDB 1A

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