Question 1

In a dihybrid cross between two pea plants with genotypes $$RrGg 	imes RrGg$$, what is the expected phenotypic ratio among the F2 offspring if the genes assort independently?

Accepted Answer

9:3:3:1

Question 2

Which of the following best explains Mendel's law of independent assortment?

Accepted Answer

Alleles of different genes segregate independently during gamete formation.

Question 3

A plant with genotype $$RrGg is $$testcrossed with $$rrgg. $$What proportion of the offspring is expected to have the genotype $$RrGg$$?

Accepted Answer

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

Question 4

In a chi-square test, the formula is $$\$$chi^2$$ = \sum \frac{(O-E)^2$}{E}. If $$you have 4 phenotypic classes, what is the degrees of freedom (df) for this test?

Accepted Answer

3

Question 5

A dihybrid $$RrGg$$ plant produces gametes. What is the probability of producing a gamete with genotype $$rg$$?

Accepted Answer

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

Question 6

Which of the following is a real-world consequence of independent assortment at the chromosomal level?

Accepted Answer

It increases genetic diversity in sexually reproducing populations.

Question 7

If a plant with genotype $$RrGg$$ self-fertilizes, what fraction of the offspring will be homozygous for both traits ($$RRGG or$$ $$rrgg$$)?

Accepted Answer

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

Question 8

A chi-square value of $$0.511 is $$calculated for a dihybrid cross with 3 degrees of freedom. According to the chi-square table, what can you conclude?

Accepted Answer

The data are consistent with independent segregation.

Question 9

Which of the following gamete genotypes can be produced by an individual with genotype $$FfQq$$?

Accepted Answer

FQ, Fq, fQ, fq

Question 10

In Mendel's pea experiments, the gene for seed shape ($$R) $$encodes an enzyme that converts amylose to amylopectin. What is the molecular basis for wrinkled seeds in $$rr$$ plants?

Accepted Answer

They lack the enzyme, so seeds accumulate amylose, which attracts water and causes wrinkling as seeds mature.

Question 11

A plant with genotype $$RrGg is $$crossed with $$rrgg. $$What is the expected phenotypic ratio among the offspring?

Accepted Answer

1:1:1:1

Question 12

Which of the following statements about autosomal dominant inheritance is FALSE?

Accepted Answer

Individuals who have the disease are often born to parents who do not have the disease.

Question 13

In a pedigree, a trait appears in every generation and affects both males and females equally. What is the most likely mode of inheritance?

Accepted Answer

Autosomal dominant

Question 14

A woman who is heterozygous for an X-linked recessive disorder has children with a man who does not have the disorder. What is the probability that their son will have the disorder?

Accepted Answer

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

Question 15

Which of the following is a hallmark of X-linked recessive inheritance?

Accepted Answer

The trait is expressed much more often in males than in females.

Question 16

In a family, two unaffected parents have a child with an autosomal recessive disorder. What is the probability that their next child will also have the disorder?

Accepted Answer

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

Question 17

A test cross is performed between an individual of unknown genotype and a homozygous recessive tester. What is the main purpose of this cross?

Accepted Answer

To determine the genotype of the unknown individual by analyzing the phenotypes of the offspring.

Question 18

Which of the following best describes the expected outcome of a reciprocal cross involving an X-linked gene in Drosophila?

Accepted Answer

The phenotypic ratios in male and female progeny will differ depending on which parent carries the X-linked allele.

Question 19

If a rare autosomal recessive disease appears in a child whose parents are unaffected, what is the most likely explanation?

Accepted Answer

Both parents are heterozygous carriers of the mutant allele.

Dihybrid Crosses and the Law of Independent Assortment: Mendelian Genetics Study Guide

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