Exam 4

Question 1

4 events in cell division

Answer 1

• Reproductive signal: initiates cell division, can be intracellular or extracellular
• Replication of DNA
• Segregation: distribution of DNA into each of the two new cells
• Cytokinesis: separation of cellular material into the two new cells

Question 2

Prokaryotic cell division

Answer 2

Also called binary fission, prokaryotes only have one chromosome, folded and circular.
- ori (origin): where replication starts
- ter (terminus): where replication ends
DNA moves through replication of proteins, in rapidly dividing prokaryotes, DNA replication occupies entire time between cell divisions

Question 3

Reproductive signals in prokaryotes

Answer 3

External factors (e.g., nutrient concentration and environmental conditions)

Question 4

Ori regions

Answer 4

When replication is complete, the ori regions move toward opposite ends of the cell, segregating the daughter DNA molecules

Question 5

Reproductive signals in eukaryotes

Answer 5

related to the needs/function of the entire organism

Question 6

Sister chromatids

Answer 6

newly replicated chromosomes closely associated with one another

Question 7

Homologous pairs

Answer 7

two chromosomes that are the same size and shape, and contain the same genes in the same order

Question 8

Mitosis

Answer 8

process that segregates newly replicated chromosomes into two new nuclei

Question 9

Somatic cells

Answer 9

any cell in the body of a multicellular organism that is not a reproductive cell

Question 10

Meiosis

Answer 10

a type of cell division that occurs in sexually reproducing organisms to produce gametes, or sex cells (sperm and eggs)

Question 11

3 broad stages of cell cycle

Answer 11

interphase, mitosis and cytokinesis, 23
hours in interphase, 1 hour in mitosis/cytokinesis

Question 12

3 subphases of interphase

Answer 12

G1, S, and G2

Question 13

G1

Answer 13

Chromosomes are single and associated with proteins
- Duration can be minutes or years
- G0: inactive resting phase, Cells enter if not preparing for cell division, cells must be stimulated by growth factors to divide

Question 14

S

Answer 14

DNA replicates: sister chromatids remain together

Question 15

G2

Answer 15

cell prepares for mitosis

Question 16

Restriction (R) point (aka G1‐to‐S
transition)

Answer 16

commitment to DNA replication and subsequent cell division

Question 17

Kinase

Answer 17

enzyme that catalyzes transfer of a phosphate group from ATP to a
target protein

Question 18

Cdks

Answer 18

Cyclin‐dependent kinases, control progress through the cell cycle

Question 19

Cyclins

Answer 19

allosterically regulates cdks

Question 20

Phosphorylation

Answer 20

addition of a phosphate group

Question 21

Cyclin cdks

Answer 21

act as cell cycle checkpoints – they regulate progression, e.g., at checkpoint R, if DNA is damaged, p21 protein is made
* p21 binds to G1 cdks, preventing their activation
* Cell cycle pauses while DNA is repaired

Question 22

RB

Answer 22

retinoblastoma protein, progress past restriction point depends on this, RB normally inhibits cell cycle, when RB is phosphorylated by cyclin‐cdk, it becomes inactive and no longer blocks cell cycle

Question 23

Nucleosomes

Answer 23

beadlike units formed by the interaction of the histones and DNA, has 8 histone proteins: 2x H2A, H2B, H3, and H4

Question 24

Chromatin

Answer 24

DNA molecules bound to proteins

Question 25

Cohesins

Answer 25

proteins that hold together sister chromatids during G2, except at centromere - DNA sequence that joins sister chromatids together, creating a short arm and a long arm on the chromatids

Question 26

Apoptosis

Answer 26

Programmed cell death, cells may no longer be needed or are prone to genetic damage that can lead to cancer

Question 27

What initiates apoptosis

Answer 27

hormones, growth factors, viral infections, toxins, extensive DNA damage

Question 28

Tumors

Answer 28

large mass of cells

Question 29

Benign vs. malignant tumor

Answer 29

Benign tumors: grow slowly, resemble the tissue they grow from, are encapsulated and remain localized Malignant tumors: do not resemble the parent tissue

Question 30

Oncogene

Answer 30

positive regulators in cancer cells - Normal regulators mutated to be overactive or present in excess

Question 31

Tumor suppressor

Answer 31

negative regulators such as RB are inactive in cancer cells