Question 1

Which of the following processes directly increases genetic variation during sexual reproduction?

Accepted Answer

Crossing over during prophase I of meiosis

Question 2

If a diploid organism has a genotype AaBb, how many unique gametes can it produce, assuming independent assortment and no crossing over?

Accepted Answer

$$4$$

Question 3

Which event during meiosis is most responsible for the formation of gametes with an abnormal number of chromosomes, such as in Triple X syndrome?

Accepted Answer

Nondisjunction during anaphase I or II

Question 4

A couple, both carriers for a recessive genetic disorder, have a child. What is the probability that their child will be affected by the disorder?

Accepted Answer

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

Question 5

Which of the following best explains why siblings from the same parents can look very different from each other?

Accepted Answer

Random assortment of chromosomes and crossing over during meiosis

Question 6

If a human cell undergoes meiosis and nondisjunction occurs during anaphase II, what is the possible outcome for the resulting gametes?

Accepted Answer

Some gametes will have an extra chromosome, some will be missing one

Question 7

Which of the following is NOT a source of genetic variation in sexually reproducing organisms?

Accepted Answer

Replication of chromosomes during mitosis

Question 8

A geneticist observes that a child has three X chromosomes. Which process most likely failed during gamete formation?

Accepted Answer

Nondisjunction

Question 9

Which of the following best describes the outcome of independent assortment during meiosis?

Accepted Answer

Each gamete receives a random mix of maternal and paternal chromosomes

Question 10

If two heterozygous parents (Aa) have children, what is the expected genotypic ratio among their offspring?

Accepted Answer

$$1:2:1 (AA$$:Aa:aa)

Question 11

Which of the following scenarios would most likely result in a child with a genetic disorder caused by nondisjunction?

Accepted Answer

A gamete with two copies of chromosome 21 fuses with a normal gamete

Question 12

Which of the following equations correctly represents the number of possible gamete combinations due to independent assortment for an organism with $$n$$ pairs of chromosomes?

Accepted Answer

$$2^n$$

Question 13

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

Accepted Answer

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

Question 14

Which of the following best explains why fertilization increases genetic variation?

Accepted Answer

It combines chromosomes from two genetically unique gametes

Question 15

Which of the following is an example of a phenotype resulting from a dominant allele?

Accepted Answer

A child with brown eyes born to two heterozygous parents (Bb)

Question 16

If a cell with 8 chromosomes undergoes meiosis, how many chromosomes will each resulting gamete have?

Accepted Answer

$$4$$

Question 17

Which of the following statements about crossing over is correct?

Accepted Answer

It occurs during prophase I of meiosis and increases genetic diversity

Question 18

A couple has a child with a genetic disorder caused by a single recessive allele. Neither parent shows symptoms. What is the most likely genotype of the parents?

Accepted Answer

Both are heterozygous carriers

Question 19

Which of the following best describes the effect of nondisjunction during meiosis?

Accepted Answer

It results in gametes with abnormal numbers of chromosomes

Question 20

Which of the following is a direct result of independent assortment and crossing over?

Accepted Answer

Genetic variation among offspring

5.2 Meiosis and Genetic Diversity

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