Chap 12 - The cell cycle

cell division

splitting of cell DNA in the nucleus

chromatin condenses into chromosomes

1 cell gives rise to genetically identical daughter cells

multicellular eukaryotes = embryonic dev

single cell prokaryotes = new organisms

Karyotype

full set of chromosomes

Chromosomes

Human somatic cells

46 chromosome (diploid, 2N) 23 pairs

each has centromere and arms

telemeres

found on ends

prevent sticking, shorten with each cell division, related to aging

Mitosis

2N → 2N

number of chromosomes remains the same

division of chromosomes into daughter cells

Meisosis

2N→ N

Number of chromosomes is halved

Interphase

time in between cell divisions

divided into G1, S, G2

Cytokenesis

Division of cytoplasm

G1 (gap 1)

RNA, proteins, organelles, synthesized

centrosome replicates

each contain 2 centrioles = bundles of microtubules

S (Synthesis)

DNA Replicated/sister chromatids form

G2 (Gap 2)

Mitochondria divide, spindle fibers form

Prophase - Mitosis

chromosomes condense

nuclear envelope disappears

centrosomes migrate

spindle fibers (microtubules) attach to centromeres of chromosome

Cytokinesis - animal cells

cleavage, 1st sign is a cleavage furrow

Cleavage furrow

shallow groove in the cell surface near the old metaphase

Cytokinesis - Plant cell

cell plate forms from cytokinesis

G1 ( Main checkpoint 1)

only opportunity to go to G0 state

DNA integrity and protein amounts checked (non-dividing)

G2 (Main checkpoint 2)

checkpoint for DNA mistakes/damage repairs

Metaphase (Main checkpoint 3)

check for attachment to spindle fibers

Kinases

regulatory protein of the cell cycle

enzymes that activate or inactivate other proteins by phosphorylation

Cyclin

regulatory protein

proteins that fluctuate in concentration in the cell

Cyclin dependent kinases (CDKs)

only active when bound to cyclins (allow mitosis)

G0 phase

mature nerve and muscle cells remain can re-enter G1 (liver cells)

Growth factors

external signal

produced by one cells and tells other cells to divide

activate kinases

Density dependent inhibition

external signal

presence of surrounding cells stops cell division

membrane proteins communicate with cytoskeleton