Cell division - mitosis

Question 1

The cell cycle

Cell division - mitosis

Answer 1

G1 - Cell grows and new organelles & proteins are made
S - Cell replicates its DNA ready to divide by mitosis
G2 - Cell keeps growing and proteins needed for cell division are made

Question 2

Interphase

Cell division - mitosis

Answer 2

Cell carries out normal functions while preparing to divide
DNA is unravelled & replicated/doubled
Organelles are also replicated and ATP content is increased

Question 3

Structure of chromosomes

Answer 3

Two strands joined in the middle by a centromere
Seperate strands are called chromatids
Two strands on same chromosome are called sister chromatids

Question 4

Prophase

Cell division - mitosis

Answer 4

Chromosomes condense, getting shorter & fatter
Centrioles start moving to opposite poles of cell, forming network of spindle fibres across the cell
Nuclear envelope breaks down and chromosomes lie free in cytoplasm

Question 5

Metaphase

Cell division - mitosis

Answer 5

Chromosomes line up along middle of cell and become attached to spindle by their centromere

Question 6

Anaphase

Cell division - mitosis

Answer 6

Centromeres divide, seperating each pair of sister chromatids
Spindles contract, pulling chromatids to opposite poles of the cell, centromere first
This makes chromatids appear v-shaped

Question 7

Telophase

Cell division - mitosis

Answer 7

Chromatids reach opposite poles on spindle
Uncoil and become long & thin again
Nuclear envelope forms around each group of chromosomes - there are no 2 nuclei

Question 8

Cytokinesis

Answer 8

Part of telophase

Division of cytoplasm
There are now two genetically identical daughter cells
Mitosis is finished & each daughter cell starts interphase

Question 9

Cancer

Cell division - mitosis

Answer 9

Mitosis & cell cycle are controlled by genes
If there’s a mutation in a gene that controls cell division, cells can grow out of control
Cells keep on dividing to make more cells which form a tumour
Cancer is a tumour that invades surrounding tissue

Question 10

Cancer treatments

Cell division - mitosis

Answer 10

Some treatments for cancer are designed to control rate of cell divison in tumour cells by disrupting cell cycle - kills tumour cells
These treatments don’t distinguish between normal & tumour cells - also kill normal body cells that are dividing
However, tumour cells divide more frequently than normal cells - treatments more likely to kill tumour cells