The Cell Cycle

Question 1

Why do cells need to divide?

Answer 1

Repair, Growth, Reproduction

Question 2

G1 - Interphase

stage 1

Answer 2

first growth of cell at mature size
cell doesn’t divide
preparation for DNA replication

Question 3

S (synthesis)- Interphase

stage 2

Answer 3

DNA replication - each of the 46 chromosomes are duplicated (sister chromatids)
critical to successful cell division (tightly regulated)

Question 4

G2 - Interphase

stage 3

Answer 4

rapid cell growth
organelles split into two cells
produce new protiens

Question 5

Mitosis/Meiosis

stage 4

Answer 5

Nuclear Division

4 phases - prophase, metaphase, anaphase, telophase

Question 6

Cytokinesis

stage 5

Answer 6

cytoplasm is divided (happens at the same time as telophase)
membrane cleavages into its self until both ends meet - creates two cells
two smaller but identical cells

Question 7

G0

stage 6

Answer 7

resting phase

cell is neither dividing or preparing to divide

Question 8

Mitosis

Answer 8

divides once, DNA replicates, two daughter cells, diploid, 2n = 46 chromosomes, function: growth repair
eg. skin or stomach

Question 9

Prophase

Answer 9

DNA super condenses
- nuclear membrane starts to disappear
two centrioles move to oppiste poles

Question 10

Prophase

Answer 10

DNA super condenses
- nuclear membrane starts to disappear
two centrioles move to opposite poles

Question 11

Metaphase

Answer 11

nuclear membrane is gone
chromosomes at an imaginary midline
spindle fibres attach to centrioles

Question 12

Anaphase

Answer 12

spindle fibres pull chromotains apart
move to either side of the cell
- ensures that each cell has an identical chromosome

Question 13

How does Mitosis work?

Answer 13

Starts out with one parental cell and replicates to two daughter cells. They have the exact same contents but smaller

Question 14

Meiosis

Answer 14

divides twine, four daughter cells, haploid, n=23 chromosomes, DNA replicates, makes gametes
eg. sperm, egg (ovum)

Question 15

Meiosis I

Answer 15

Segregation - homologous pairs are separated reducing chromosome number by half
4 phases of mitosis are undergone
- results in two cells

Question 16

Meiosis II

Answer 16

Haploid gametes - sister chromatids are sepreated producing four haploid cells
4 phases of mitois again on both cells
- resulting in four cells

Question 17

How does Meiosis work?

Answer 17

cells undergo meiosis require 2 sets of divisions because only the chromosomes from each parent are needed
- half of the offprings genes come from each parent