UNIT 5: Cell Communication and Reproduction -Biology 1112–13/5/2020

Question 1

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What property prevents the ligands of cell-surface receptors from entering the cell?

Select one:

a. The molecules bind to the extracellular domain.

b. The molecules are hydrophilic and cannot penetrate the hydrophobic interior of the plasma membrane.

c. The molecules are attached to transport proteins that deliver them through the bloodstream to target cells.

d. The ligands are able to penetrate the membrane and directly influence gene expression upon receptor binding.

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Question 2

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The secretion of hormones by the pituitary gland is an example of __________.

Select one:

a. autocrine signaling

b. paracrine signaling

c. endocrine signaling

d. direct signaling across gap junctions

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Question 3

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Why are ion channels necessary to transport ions into or out of a cell?

Select one:

a. Ions are too large to diffuse through the membrane.

b. Ions are charged particles and cannot diffuse through the hydrophobic interior of the membrane.

c. Ions do not need ion channels to move through the membrane.

d. Ions bind to carrier proteins in the bloodstream, which must be removed before transport into the cell.

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Question 4

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Where do DAG and IP3 originate?

Select one:

a. They are formed by phosphorylation of cAMP.

b. They are ligands expressed by signaling cells.

c. They are hormones that diffuse through the plasma membrane to stimulate protein production.

d. They are the cleavage products of the inositol phospholipid, PIP2.

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Question 5

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What property enables the residues of the amino acids serine, threonine, and tyrosine to be phosphorylated?

Select one:

a. They are polar.

b. They are non-polar.

c. They contain a hydroxyl group.

d. They occur more frequently in the amino acid sequence of signaling proteins.

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Question 6

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A diploid cell has __________ the number of chromosomes as a haploid cell.

Select one:

a. one-fourth

b. half

c. twice

d. four times

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Question 7

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An organism’s traits are determined by the specific combination of inherited __________.

Select one:

a. cells.

b. genes.

c. proteins.

d. chromatids.

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Question 8

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The first level of DNA organization in a eukaryotic cell is maintained by which molecule?

Select one:

a. cohesin

b. condensin

c. chromatin

d. histone

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Question 9

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Chromosomes are duplicated during what stage of the cell cycle?

Select one:

a. G1 phase

b. S phase

c. prophase

d. prometaphase

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Question 10

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Which of the following events does not occur during some stages of interphase?

Select one:

a. DNA duplication

b. organelle duplication

c. increase in cell size

d. separation of sister chromatids

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Question 11

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The mitotic spindles arise from which cell structure?

Select one:

a. centromere

b. centrosome

c. kinetochore

d. cleavage furrow

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Question 12

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At which of the cell cycle checkpoints do external forces have the greatest influence?

Select one:

a. G1 checkpoint

b. G2 checkpoint

c. M checkpoint

d. G0 checkpoint

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Question 13

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What is the main prerequisite for clearance at the G2 checkpoint?

Select one:

a. cell has reached a sufficient size

b. an adequate stockpile of nucleotides

c. accurate and complete DNA replication

d. proper attachment of mitotic spindle fibers to kinetochores

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Question 14

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If the M checkpoint is not cleared, what stage of mitosis will be blocked?

Select one:

a. prophase

b. prometaphase

c. metaphase

d. anaphase

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Question 15

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__________ are changes to the order of nucleotides in a segment of DNA that codes for a protein.

Select one:

a. Proto-oncogenes

b. Tumor suppressor genes

c. Gene mutations

d. Negative regulators

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Question 16

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A gene that codes for a positive cell cycle regulator is called a(n) __________.

Select one:

a. kinase inhibitor.

b. tumor suppressor gene.

c. proto-oncogene.

d. oncogene.

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Question 17

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Which eukaryotic cell cycle event is missing in binary fission?

Select one:

a. cell growth

b. DNA duplication

c. karyokinesis

d. cytokinesis