cell bio exam 3: cell cycle & control system

what is the central goal of the cell cycle?

to pass genetic information to the next generation by duplicating contents and dividing in two

cell division is essential for

• reproduction

• growth/development

• tissue maintenance (balancing cell growth and death)

• tissue repair

4 phases of the cell cycle

• G1

• S

• G2

• M

what is the cell cycle for a typical human cell?

• 24 hours:

• interphase (G phases + S phase) = 23 hrs

• mitosis is less than 1 hr

major events at each stage of the mammalian cell cycle

• G1 → cells grow, proteins form, organelles form

• S → DNA replication, centrosome duplication

• G2 → centrosome separation, DNA is chromatids

• M → 6 stages of mitosis

6 stages of mitosis

• prophase

• prometaphase

• metaphase

• anaphase

• telophase

• cytokinesis

prophase

• chromosomes condense

• centrosomes migrate

• spindle formation

prometaphase

• nuclear envelope breaks down

• spindle attaches to kinetochores on sister chromatids

metaphase

• chromosomes align at central plate

anaphase

• chromosome separation

• kinetochore MTs shorten

• spindles pull apart

• cytokinesis initiated

telophase

• chromosomes decondense

• nuclear envelope reforms

• spindles disassemble

cytokinesis

• actomyosin contractile ring forms

• cytoplasmic division

flow cytometry

• way to monitor cell cycle

• analysis one-by-one of a large population of cells

• rapid, quantitative

• separates individual cells from culture; must be suspended and stained

• uses proportional DNA dye

• detector detects fluorescence emitted from each cell (shows DNA content)

how many checkpoints are there in the cell cycle? what are they?

3 total

1. between G1 and S: sufficient nutrients? DNA damage? specific signal molecules present?

2. between G2 and M: is DNA intact? is all DNA replicated?

3. during M phase before cytokinesis: are all chromosomes correctly attached to spindle?

the cell cycle control system depends on

cyclically activated kinases called cyclin-dependent kinases (Cdks)

cdks are (?) kinases

serine/threonine

cdks form complexes with

cyclins - have no enzymatic activity themselves but cdk is inactive without cyclin; with cyclin, cdks can phosphorylate target proteins