Question 1

Which of the following best describes the difference between a chromosome and chromatin in a eukaryotic cell?

Accepted Answer

Chromosomes are made of DNA and protein and are visible during cell division, while chromatin is the less condensed form of DNA and protein present during interphase.

Question 2

During which stage of the cell cycle does DNA replication occur, and what is the significance of this process?

Accepted Answer

DNA replication occurs during the S phase, ensuring that each daughter cell receives an identical set of chromosomes.

Question 3

A researcher observes a cell with chromosomes aligned at the center of the cell and spindle fibers attached to the centromeres. Which stage of mitosis is being observed, and what is the main event of this stage?

Accepted Answer

Metaphase; chromosomes align at the metaphase plate, preparing for separation.

Question 4

Which of the following statements correctly compares cytokinesis in plant and animal cells?

Accepted Answer

In animal cells, a cleavage furrow forms due to actin filaments, while in plant cells, a cell plate forms from vesicles to separate the two daughter cells.

Question 5

Which checkpoint in the cell cycle is primarily responsible for ensuring that all chromosomes are properly attached to the spindle before proceeding to anaphase, and why is this important?

Accepted Answer

M checkpoint; it prevents chromosome missegregation by ensuring all kinetochores are attached to spindle fibers.

Question 6

A patient is diagnosed with a malignant tumor. Which of the following characteristics distinguishes a malignant tumor from a benign tumor?

Accepted Answer

Malignant tumors can invade nearby tissues and metastasize to distant sites, while benign tumors do not.

Question 7

Which of the following events during meiosis increases genetic variation in offspring, and during which stage does it occur?

Accepted Answer

Crossing over during prophase I

Question 8

A diploid cell with $$2n = 8$$ undergoes meiosis. How many chromosomes will each gamete contain, and what is the term for this chromosome number?

Accepted Answer

Each gamete will contain 4 chromosomes; this is the haploid number.

Question 9

Which of the following best explains Mendel's 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 10

In a monohybrid cross between two heterozygous parents ($$Aa 	imes Aa$$), what is the expected phenotypic ratio among the offspring if $$A is $$dominant to $$a$$?

Accepted Answer

$$3:1 ($$dominant phenotype : recessive phenotype)

Question 11

A woman who is a carrier for sickle cell disease ($$AS) $$and a man who has sickle cell disease ($$SS) $$have two children. What is the probability that their child will be a carrier for sickle cell disease?

Accepted Answer

$$0.5$$

Question 12

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 13

Which of the following best describes polygenic inheritance?

Accepted Answer

Multiple genes independently affect a single trait, resulting in continuous variation.

Question 14

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 for this trait?

Accepted Answer

Autosomal dominant

Question 15

Which of the following scenarios illustrates the concept of epistasis?

Accepted Answer

A gene for pigment deposition masks the expression of a gene for pigment color in Labrador retrievers.

Question 16

Which of the following best explains why cancer cells can divide uncontrollably?

Accepted Answer

They have lost the ability to respond to cell cycle control signals, such as checkpoints.

Question 17

Which of the following events is unique to meiosis and does NOT occur during mitosis?

Accepted Answer

Pairing of homologous chromosomes during prophase I

Question 18

A plant with genotype $$RrYy is $$crossed with another plant with genotype $$RrYy. $$According to Mendel's law of independent assortment, what is the expected phenotypic ratio among the offspring?

Accepted Answer

$$9:3:3:1$$

Question 19

Which of the following best describes a genetic carrier for an autosomal recessive disorder such as cystic fibrosis?

Accepted Answer

An individual who has one dominant and one recessive allele and does not express the disorder but can pass it to offspring.

Question 20

Which of the following best describes the G0 phase of the cell cycle?

Accepted Answer

A non-dividing state where cells exit the cell cycle, often to perform specialized functions.

General Biology Exam 4 Study Guide: Cell Cycle, Meiosis, and Mendelian Genetics

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