Q: A genetic cross yields 47 recombinant offspring and 153 parental offspring. What is the map distance between the two genes?

$$\frac{47}{200} \times 100 = 23.5$$ map units

Question 1

Which of the following best explains why Mendel chose the garden pea (Pisum sativum) as his model organism for studying inheritance?

Accepted Answer

It produced many offspring, had easily distinguishable traits, and allowed controlled matings.

Question 2

A plant with genotype $$Rr ($$where $$R = $$round, $$r = $$wrinkled) is crossed with another $$Rr$$ plant. What is the probability that an offspring will be homozygous dominant ($$RR) $$for seed shape?

Accepted Answer

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

Question 3

Which of the following statements about the principle of independent assortment is correct?

Accepted Answer

It states that alleles of different genes are transmitted independently of each other during gamete formation.

Question 4

In a dihybrid cross between two individuals heterozygous for both traits ($$RrYy 	imes RrYy$$), what is the expected phenotypic ratio among the offspring, assuming independent assortment?

Accepted Answer

9:3:3:1

Question 5

A woman with type AB blood ($$I^A I^B) $$and a man with type O blood ($$ii) $$have a child. What is the probability that the child will have type A blood?

Accepted Answer

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

Question 6

Which of the following best describes pleiotropy?

Accepted Answer

A single gene influences multiple traits in an organism.

Question 7

A geneticist observes that a certain trait appears more frequently in males than females and often skips generations. Which inheritance pattern is most likely responsible?

Accepted Answer

X-linked recessive

Question 8

If two genes are located close together on the same chromosome, which of the following is most likely to be true?

Accepted Answer

They are likely to be inherited together due to genetic linkage.

Question 9

A testcross is performed between a plant with an unknown genotype for a dominant trait and a homozygous recessive plant. If all offspring display the dominant phenotype, what is the genotype of the unknown parent?

Accepted Answer

Homozygous dominant

Question 10

In Drosophila, the gene for eye color is X-linked. If a red-eyed female (homozygous) is crossed with a white-eyed male, what will be the eye color of the F1 offspring?

Accepted Answer

All offspring will have red eyes.

Question 11

A genetic cross yields 47 recombinant offspring and 153 parental offspring. What is the map distance between the two genes?

Accepted Answer

$$\frac{47}{200} 	imes 100 = 23.5$$ map units

Question 12

Which of the following is an example of incomplete dominance?

Accepted Answer

A cross between red and white flowers produces pink flowers.

Question 13

A pedigree shows a trait that appears in every generation and is present in both males and females. Which inheritance pattern is most likely?

Accepted Answer

Autosomal dominant

Question 14

Which of the following best describes the effect of environment on phenotype, as seen in phenylketonuria (PKU)?

Accepted Answer

Environmental factors such as diet can prevent the expression of the disease phenotype.

Question 15

Which of the following scenarios demonstrates gene-gene interaction (epistasis)?

Accepted Answer

The expression of one gene is masked or modified by another gene.

Question 16

A man with red-green color blindness (an X-linked recessive trait) and a woman who is a carrier have a son. What is the probability that the son will be color blind?

Accepted Answer

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

Question 17

Which of the following is true about quantitative traits?

Accepted Answer

They show continuous variation and are influenced by multiple genes.

Question 18

If a male with an X-linked dominant disorder has children with a normal female, what is the expected outcome for their daughters?

Accepted Answer

All daughters will inherit the disorder.

Question 19

Which of the following best explains why linked genes do not always show perfect linkage in offspring?

Accepted Answer

Crossing over during meiosis can separate linked genes, creating recombinant genotypes.

Question 20

A pedigree shows that a rare trait is passed from an affected father to all his daughters but none of his sons. What is the most likely mode of inheritance?

Accepted Answer

X-linked dominant

Mendel and the Gene: Patterns of Inheritance and Extensions

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