Question 1

Which of the following best describes the difference between paracrine signaling and endocrine signaling in multicellular organisms?

Accepted Answer

Paracrine signaling involves local mediators affecting nearby cells, while endocrine signaling involves hormones traveling through the bloodstream to distant target cells.

Question 2

A researcher discovers a mutation that prevents a cell from producing cAMP in response to a signal. Which step in the G protein-coupled receptor (GPCR) pathway is most likely disrupted?

Accepted Answer

Adenylyl cyclase is not activated to convert ATP to cAMP.

Question 3

Which of the following best explains why only certain cells in the body respond to a particular hormone?

Accepted Answer

Only those cells have the specific receptor for that hormone.

Question 4

Which of the following statements about receptor tyrosine kinases (RTKs) is correct?

Accepted Answer

RTKs are activated by the binding of a ligand, which causes them to dimerize and autophosphorylate.

Question 5

During the cell cycle, at which checkpoint does the cell verify that all DNA has been accurately replicated before proceeding to mitosis?

Accepted Answer

G2 checkpoint

Question 6

A human somatic cell has a diploid number of $$2n = 46. $$After DNA replication during the S phase, how many chromatids are present in the cell?

Accepted Answer

$$92$$

Question 7

Which cytoskeletal component is primarily responsible for the formation of the cleavage furrow during cytokinesis in animal cells?

Accepted Answer

Actin filaments (microfilaments)

Question 8

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

Accepted Answer

Pairing and crossing over of homologous chromosomes

Question 9

During which phase of meiosis does independent assortment of chromosomes occur, and how does this process contribute to genetic variation?

Accepted Answer

Metaphase I; it allows homologous chromosomes to align randomly, resulting in new combinations of maternal and paternal chromosomes in gametes.

Question 10

A plant with genotype $$YyRr ($$yellow, round seeds) is crossed with a plant with genotype $$yyrr ($$green, wrinkled seeds). What is the expected phenotypic ratio among the offspring?

Accepted Answer

1 yellow round : 1 yellow wrinkled : 1 green round : 1 green wrinkled

Question 11

A cell is observed to have 12 chromosomes at the start of mitosis. After cytokinesis, how many chromosomes will each daughter cell have?

Accepted Answer

$$12$$

Question 12

Which of the following best describes the function of a phosphatase enzyme in cell signaling?

Accepted Answer

It removes phosphate groups from proteins, often deactivating them.

Question 13

In Mendel's monohybrid cross between true-breeding purple-flowered and white-flowered pea plants, what was the phenotypic ratio observed in the F2 generation?

Accepted Answer

3 purple : 1 white

Question 14

A woman with genotype $$Aa$$ for a dominant trait marries a man with genotype $$aa. $$What is the probability that their child will display the dominant phenotype?

Accepted Answer

$$0.5$$

Question 15

Which of the following scenarios best illustrates the law of independent assortment?

Accepted Answer

A plant with genotype $$YyRr$$ produces gametes with all possible combinations of $$Y or$$ $$y$$ and $$R or$$ $$r$$ alleles.

Question 16

If a cell fails the M checkpoint during mitosis, what is the most likely consequence?

Accepted Answer

The cell will undergo apoptosis or arrest until the problem is fixed.

Question 17

In the nematode worm C. elegans, apoptosis is a crucial process during development. Which of the following best describes apoptosis?

Accepted Answer

Programmed cell death involving a cascade of specific cellular events.

Question 18

A testcross is performed between a plant with an unknown genotype for a dominant trait and a homozygous recessive plant. If all offspring display the dominant phenotype, what is the genotype of the unknown parent?

Accepted Answer

Homozygous dominant

Question 19

Which of the following best describes the difference between homologous chromosomes and sister chromatids?

Accepted Answer

Homologous chromosomes are similar chromosomes from each parent, while sister chromatids are identical copies formed after DNA replication.

Question 20

A couple, both heterozygous for two genes ($$AaBb$$), have a child. What is the probability that the child will be homozygous recessive for both genes ($$aabb$$)? Use the multiplication rule.

Accepted Answer

$$\frac{1}{16}$$

Cell Communication, Cell Cycle, Meiosis, and Mendelian Genetics: Study Guide for Chapters 11-14

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