Question 1

Which of the following best explains why siblings from the same parents are not genetically identical?

Accepted Answer

Crossing over and independent assortment during meiosis create unique combinations of alleles.

Question 2

During which phase of meiosis does crossing over occur, and what is its significance?

Accepted Answer

Prophase I; it increases genetic variation by exchanging DNA between homologous chromosomes.

Question 3

If a human cell has 46 chromosomes, how many chromosomes will each gamete have after meiosis?

Accepted Answer

$$23$$

Question 4

Which process restores the diploid number of chromosomes in humans after meiosis?

Accepted Answer

Fertilization

Question 5

A mutation occurs in a gene located at a specific locus on a chromosome. What is the most likely result?

Accepted Answer

A new allele may be created, contributing to genetic variation.

Question 6

Which of the following is unique to meiosis I and does NOT occur in mitosis?

Accepted Answer

Synapsis of homologous chromosomes

Question 7

How many possible combinations of chromosomes can be produced in human gametes due to independent assortment alone?

Accepted Answer

$$2^{23}$$

Question 8

Which of the following best describes the outcome of meiosis II?

Accepted Answer

Four genetically unique haploid cells are produced.

Question 9

In a plant species with a haploid number $$n = 8$$, how many different combinations of chromosomes are possible in its gametes due to independent assortment?

Accepted Answer

$$2^8 = 256$

Question 10

Which event during meiosis contributes most directly to the formation of recombinant chromosomes?

Accepted Answer

Crossing over during prophase I

Question 11

A karyotype is prepared from a human somatic cell. How many pairs of homologous chromosomes should be visible?

Accepted Answer

$$23$$

Question 12

Which of the following statements about sexual and asexual reproduction is correct?

Accepted Answer

Sexual reproduction increases genetic variation among offspring.

Question 13

Which life cycle is characterized by a multicellular haploid stage and a multicellular diploid stage?

Accepted Answer

Plant and some algae life cycle

Question 14

If a diploid cell undergoes meiosis, how many total chromosomes will be present in each resulting gamete compared to the original cell?

Accepted Answer

Half as many

Question 15

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

Accepted Answer

Replication of DNA during S phase

Question 16

A geneticist observes that a child has a trait not present in either parent. Which process most likely explains this observation?

Accepted Answer

Crossing over during meiosis

Question 17

Which of the following equations correctly represents the chromosome number change during fertilization in humans?

Accepted Answer

$$n + n \rightarrow 2n$$

Question 18

Which stage of meiosis is responsible for reducing the chromosome number from diploid to haploid?

Accepted Answer

Meiosis I

Question 19

Why is random fertilization a significant source of genetic variation?

Accepted Answer

It combines gametes with different genetic backgrounds, increasing possible combinations.

Question 20

Which of the following best describes the relationship between a gene, its locus, and a trait?

Accepted Answer

A locus is the physical location of a gene on a chromosome, and the gene codes for a trait.

Meiosis and Sexual Life Cycles: Mechanisms of Genetic Variation

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