final cell cycle

Question 1

how do somatic cells divide

Answer 1

by mitosis

Question 2

how do sperm and egg cells (germ cells) generate

Answer 2

meiosis, which halves the DNA content per cell

Question 3

what are the phases of the cell cycle

Answer 3

DNA synthesis phase (S phase) and a mitosis phase (M phase) with gap phases (G1 and G2)

Question 4

what is progression through the phases of the cell cycle controlled by

Answer 4

cyclin-Cdks and checkpoint control proteins

Question 5

when are DNA and histones replicated

Answer 5

during S phase - DNA is held together as sister chromatids

Question 6

what happens during the M phase

Answer 6

sister chromatids condense, attach to spindle
microtubules, and are segregated. After DNA segregation, the cytoplasm is
divided between the two daughter cells by cytokinesis

Question 7

what is the default state of most cells in a fully-developed organism

Answer 7

G1 phase - activation of G1-Cdk and G1/S-Cdk enables cells to enter the cell cycle

Question 8

what are the three main classes of signals that can activate the cell cycle

Answer 8

mitogens, growth factors, and survival factors

Question 9

what are the four phases of the cell cycle

Answer 9

S phase: DNA Synthesis
G2: Gap 2 phase
M phase: Mitosis and cytokinesis
G1: Gap 1 phase

Question 10

what is interphase

Answer 10

G1 phase + S phase + G2 phase

Question 11

when in the cell cycle does cell growth not occur

Answer 11

mitosis

Question 12

how is the cell cycle studied

Answer 12

through yeast

Question 13

what are keys to understanding cell cycle

Answer 13

temp-sensitive cell division cycle (cdc) mutants

Question 14

what are the three checkpoints of the cell cycle

Answer 14

• start checkpoint: check if environment is favorable to enter cell cycle and proceed to S phase
• G2/M checkpoint: checks if all DNA is replicated and if environment is favorable to enter mitosis
• Metaphase-to-anaphase transition: checks if all chromosomes are attached to the spindle to trigger anaphase and proceed to cytokinesis

Question 15

what does control of cell cycle depend on

Answer 15

cyclically activated cyclin-dependent kinases (4 - one for each phase)

Question 16

how are cdks held inactive

Answer 16

with a bound ATP in the absence of cyclins

Question 17

what are two examples of regulation of cell cycle via degradation

Answer 17

• degradation of M-cyclin by the APC/C

- degradation of CKI by the SCF complex

Question 18

what does S-cdk do

Answer 18

initiates DNA replication once per cycle

Question 19

what holds together replicated sister chromatids

Answer 19

cohesin complex - ensures appropriate position in cells

Question 20

what is the M phase activated though

Answer 20

positive feedback - inhibition of inhibitor and activator of activator

Question 21

what is the condensin complex

Answer 21

in the M phase - gets duplicated chromosomes ready for separation

Question 22

what does the mitotic spindle do

Answer 22

separates the sister chromatids

Question 23

what are the three kinds of microtubules in the mitotic spindle

Answer 23

• astral microtubules – bind to cell cortex
• kinetochore
  microtubules – bind to chromosomes
• interpolar microtubules – slide
  past each other through the action of motors

Question 24

what are the three classes of extracellular signal molecules that can control the cell cycle

Answer 24

• mitogens, which stimulate cell division
• growth factors, which stimulate cell growth
• survival factors, which promote cell survival