Question 1

During meiosis, genetic variation is introduced through two key processes. Which of the following correctly identifies both processes and the stages at which they occur?

Accepted Answer

Crossing over during prophase I and independent assortment during metaphase I

Question 2

A human cell with 46 chromosomes undergoes meiosis. What is the chromosome number in each resulting gamete, and what term describes this number?

Accepted Answer

23 chromosomes; haploid

Question 3

A woman who is heterozygous for a recessive X-linked disorder (X$$^NX$^n) $$has children with a man who is unaffected (X$$^NY). $$What is the probability that their son will have the disorder?

Accepted Answer

$$0.5$$

Question 4

Which of the following best explains why more males than females express X-linked recessive traits?

Accepted Answer

Males have only one X chromosome, so a single recessive allele will result in the trait being expressed.

Question 5

A plant with red flowers (RR) is crossed with a plant with white flowers (WW). All offspring have pink flowers. Which pattern of inheritance does this demonstrate?

Accepted Answer

Incomplete dominance

Question 6

In a dihybrid cross between two heterozygous pea plants (RrYy × RrYy), what is the expected phenotypic ratio of the offspring, assuming independent assortment?

Accepted Answer

$$9:3:3:1$$

Question 7

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

Accepted Answer

Autosomal dominant

Question 8

Which event during meiosis is most likely to result in a child with Down syndrome (trisomy 21)?

Accepted Answer

Nondisjunction during anaphase I or II

Question 9

A man with blood type AB and a woman with blood type O have children. Which blood types are possible for their children?

Accepted Answer

A and B only

Question 10

Which of the following best describes the Law of Independent Assortment?

Accepted Answer

Alleles of different genes assort independently of one another during gamete formation.

Question 11

A karyotype is prepared from a patient's cells. The karyotype shows 47 chromosomes, including three copies of chromosome 18. What is the best description of this condition?

Accepted Answer

Trisomy 18 (Edwards syndrome)

Question 12

Which of the following is an example of polygenic inheritance?

Accepted Answer

Human skin color

Question 13

If a trait is controlled by multiple alleles, which of the following is true?

Accepted Answer

There are more than two possible alleles for the gene in the population.

Question 14

A genetic counselor is analyzing a pedigree for a rare genetic disorder. The disorder skips generations and affects males and females equally. What is the most likely inheritance pattern?

Accepted Answer

Autosomal recessive

Question 15

Which of the following statements about homologous chromosomes is correct?

Accepted Answer

They carry the same genes in the same order but may have different alleles.

Question 16

A couple has a child with cystic fibrosis, an autosomal recessive disorder. Neither parent has the disorder. What are the genotypes of the parents?

Accepted Answer

Both are heterozygous carriers

Question 17

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

Accepted Answer

Genotype is the genetic makeup; phenotype is the observable trait.

Question 18

Which of the following scenarios demonstrates codominance?

Accepted Answer

A person with type AB blood expresses both A and B antigens equally.

Question 19

If a cell starts meiosis with a diploid number of $$2n = 8$$, how many chromosomes will each gamete have after meiosis is complete?

Accepted Answer

$$4$$

Question 20

A woman with genotype AaBb (for two unlinked genes) produces eggs. According to the law of independent assortment, what is the probability that an egg will contain the alleles a and b?

Accepted Answer

$$0.25$$

Meiosis and Genetics: Study Guide for College Biology

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