Question 1

Which of the following best explains why mitosis results in genetically identical daughter cells?

Accepted Answer

Because each chromosome is duplicated and the sister chromatids are separated into two cells, ensuring each cell receives an identical set of chromosomes.

Question 2

A human somatic cell contains 46 chromosomes. After S phase but before mitosis, how many chromatids and DNA molecules are present in the cell?

Accepted Answer

92 chromatids and 92 DNA molecules

Question 3

Which of the following scenarios would most likely result in uncontrolled cell division (cancer)?

Accepted Answer

A mutation that disables a checkpoint protein, allowing cells to proceed through the cell cycle without proper regulation.

Question 4

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

Accepted Answer

Crossing over occurs during prophase I and increases genetic diversity among gametes.

Question 5

A diploid organism has a genotype AaBb for two unlinked genes. Which of the following lists all possible gamete genotypes this organism can produce, and what process explains this result?

Accepted Answer

AB, Ab, aB, ab; explained by independent assortment during meiosis I.

Question 6

Which of the following best describes the difference between autosomal and sex chromosomes in humans?

Accepted Answer

Autosomal chromosomes are present in pairs in both sexes, while sex chromosomes differ between males (XY) and females (XX).

Question 7

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

Accepted Answer

Autosomal dominant

Question 8

If a cell is treated with a drug that prevents microtubule depolymerization during anaphase, what is the most likely outcome?

Accepted Answer

Sister chromatids will not separate, resulting in cells with abnormal chromosome numbers.

Question 9

Which of the following best explains why males are more likely than females to express X-linked recessive disorders?

Accepted Answer

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

Question 10

In a cross between two heterozygous individuals for a single gene (Aa x Aa), what is the expected genotypic ratio among the offspring?

Accepted Answer

$$1\;AA : 2\;Aa : 1\;aa$$

Question 11

Which of the following is an example of incomplete dominance?

Accepted Answer

A red-flowered plant crossed with a white-flowered plant produces pink-flowered offspring.

Question 12

Which statement best describes the law of segregation?

Accepted Answer

Each individual has two alleles for each gene, which separate during gamete formation so that each gamete receives only one allele.

Question 13

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

Accepted Answer

$$0.25$$

Question 14

Which of the following best describes the difference between a gene and an allele?

Accepted Answer

A gene is a segment of DNA that codes for a trait, while an allele is a specific version of that gene.

Question 15

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

Accepted Answer

They are likely to be inherited together unless crossing over occurs between them.

Question 16

Which of the following best explains how independent assortment contributes to genetic diversity?

Accepted Answer

It results in the random orientation of homologous chromosome pairs during metaphase I of meiosis, producing gametes with different combinations of maternal and paternal chromosomes.

Question 17

A plant with genotype AaBb is testcrossed with aabb. If the genes are unlinked, what is the expected phenotypic ratio among the offspring?

Accepted Answer

$$1\;A_B_ : 1\;A_bb : 1\;aaB_ : 1\;aabb$$

Question 18

Which of the following is an example of pleiotropy?

Accepted Answer

A single gene affects both the color of a flower and the shape of its leaves.

Question 19

Which of the following best describes the role of apoptosis in multicellular organisms?

Accepted Answer

It removes damaged or unnecessary cells, helping regulate cell number and prevent cancer.

Cell Division, Genetics, and Inheritance: Study Guide Notes

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