final cell cycle Flashcards
how do somatic cells divide
by mitosis
how do sperm and egg cells (germ cells) generate
meiosis, which halves the DNA content per cell
what are the phases of the cell cycle
DNA synthesis phase (S phase) and a mitosis phase (M phase) with gap phases (G1 and G2)
what is progression through the phases of the cell cycle controlled by
cyclin-Cdks and checkpoint control proteins
when are DNA and histones replicated
during S phase - DNA is held together as sister chromatids
what happens during the M phase
sister chromatids condense, attach to spindle
microtubules, and are segregated. After DNA segregation, the cytoplasm is
divided between the two daughter cells by cytokinesis
what is the default state of most cells in a fully-developed organism
G1 phase - activation of G1-Cdk and G1/S-Cdk enables cells to enter the cell cycle
what are the three main classes of signals that can activate the cell cycle
mitogens, growth factors, and survival factors
what are the four phases of the cell cycle
S phase: DNA Synthesis
G2: Gap 2 phase
M phase: Mitosis and cytokinesis
G1: Gap 1 phase
what is interphase
G1 phase + S phase + G2 phase
when in the cell cycle does cell growth not occur
mitosis
how is the cell cycle studied
through yeast
what are keys to understanding cell cycle
temp-sensitive cell division cycle (cdc) mutants
what are the three checkpoints of the cell cycle
- 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
what does control of cell cycle depend on
cyclically activated cyclin-dependent kinases (4 - one for each phase)
how are cdks held inactive
with a bound ATP in the absence of cyclins
what are two examples of regulation of cell cycle via degradation
- degradation of M-cyclin by the APC/C
- degradation of CKI by the SCF complex
what does S-cdk do
initiates DNA replication once per cycle
what holds together replicated sister chromatids
cohesin complex - ensures appropriate position in cells
what is the M phase activated though
positive feedback - inhibition of inhibitor and activator of activator
what is the condensin complex
in the M phase - gets duplicated chromosomes ready for separation
what does the mitotic spindle do
separates the sister chromatids
what are the three kinds of microtubules in the mitotic spindle
- astral microtubules – bind to cell cortex
- kinetochore
microtubules – bind to chromosomes - interpolar microtubules – slide
past each other through the action of motors
what are the three classes of extracellular signal molecules that can control the cell cycle
- mitogens, which stimulate cell division
- growth factors, which stimulate cell growth
- survival factors, which promote cell survival
