cell cycle

Question 1

cell cycle is important for:

Answer 1

• embryo development
• growth
• homeostasis
• cancer
• mostly occur in the bone marrow

Question 2

speed of cell cycle

Answer 2

• typical eukaryote cell - 24 hr
• hepatocyte - 1-2 yrs
• neurones, heart cells - never
• bacteria - 20 minutes

Question 3

post - mitotic cells

Answer 3

cells that never divide

Question 4

senescence cells

Answer 4

during ageing some cells lose the ability to divide

Question 5

1st stage - G1 phase

Answer 5

• protein synthesis
• cells duplicate their organelles
• cells are highly metabolically active and require lots of energy

Question 6

2nd stage - S phase

Answer 6

• cell has grown big enough and begins to duplicate its DNA
• extra copy of each chromosome is ,made and the two copies are joined at the centromere

Question 7

stage 3 - G2 phase

Answer 7

• where the cell readies itself for mitosis
• cell checks its DNA to make sure it has been copied correctly

Question 8

stage 4 - M phase

Answer 8

• fastest stage
• nuclear envelope breaks down, the mitotic spindle forms and the chromosomes are separated
• the cell then splits in two (cytokinesis)

Question 9

M phase - prophase

Answer 9

• the chromatin in the nucleus condenses into chromosomes and become visible
• the nucleolus in the nucleus disappears
• the nuclear envelope starts to break down
• microtubule activity increases at the centrosomes

Question 10

M phase - Prometaphase

Answer 10

• microtubules emerge from the spindle poles and start searching for a chromosome to capture
• one microtubule from the spindle attached to the kinetochore protein complex at the chromosomes centromere
• once another microtubule from the other spindle pole attaches to the centromere, forces exerted by protein motor moves the chromosomes towards the centre of the cell

Question 11

M phase - metaphase

Answer 11

• the chromosomes align at the centre of the cell along the metaphase plate

Question 12

kinetochore

Answer 12

• attaches chromosomes to microtubules, leading to segregation of the chromosomes

Question 13

Anaphase

Answer 13

• each chromosomes sister chromatids separate
• chromatids are cleaved by an enzyme called separase
• upon separation, every chromatid becomes an independent chromosome
• kinetochore microtubules shorten and draw each chromatid towards opposite ends of the spindle poles

Question 14

M phase - Telophase

Answer 14

• chromosomes have reached the opposite ends of the cell
• a nuclear envelope reforms upon vesicles containing the original nuclear membrane around the chromosomes forming two daughter nuclei
• the nucleolus can reform in the daughter nuclei