Cell Division

Question 1

G1 phase

Answer 1

Growth
Cells produce RNA, enzymes, and other proteins required for cell growth
Cells receive a signal to divide - controlled by cyclins

Question 2

S phase

Answer 2

Synthesis of new DNA
DNA in the nucleus replicates → each chromosome contains two identical sister chromatids

Question 3

G2 phase

Answer 3

Further cell growth
Newly synthesised DNA is checked for any errors → (normally) repaired
Tubulin is also made - protein needed for mitosis

Question 4

Mitosis

Answer 4

is a type of nuclear division where two genetically identical daughter nuclei are produced. Consists of four stages: Prophase, Metaphase, Anaphase, Telophase (PMAT)

Question 5

Centrosomes

Answer 5

are organelles that become visible during mitosis, helping to pair up & move chromosomes

Question 6

Prophase

Answer 6

Chromosomes condense
Copied chromosomes are joined together at the centromere
Centrosomes move to opposite poles → spindle fibres emerge from them
Nuclear envelope breaks down into vesicles

Question 7

Metaphase

Answer 7

Chromosomes line up at the equator of the spindle (also known as the metaphase plate)

Spindle fibres attach to the centromeres

Question 8

Anaphase

Answer 8

Sister chromatids separate at the centromere (which divides in two)

Spindle fibres shorten & pull the separated sister chromatids (now called chromosomes) pulled to opposite poles

Question 9

Telophase

Answer 9

Chromosomes arrived at opposite poles & decondense

Nuclear envelope reforms around each set of chromosomes

Spindle fibres break down

Question 10

Cytokinesis

Answer 10

is the physical separation of the parent cell into two genetically identical daughter cells

Question 11

Cytokinesis in animal cells

Answer 11

In animal cells, a ‘cleavage furrow’ (folded membrane) forms and separates the daughter cells

Question 12

Cytokinesis in plant cells

Answer 12

A ‘cell plate’ (the precursor to a new cell wall) forms at the site of the metaphase plate → new cell walls are produced → separates the new daughter cells

Question 13

Cancers arise due to

Answer 13

uncontrolled mitosis → divide repeatedly and uncontrolled → forms a tumour (irregular mass of cells)

Question 14

Mutated genes that cause cancer

Answer 14

oncogene - these mutations can persist, and can be passed on to subsequent cells

Question 15

Benign tumours

Answer 15

e.g., warts, do not spread from their original site & do not cause cancer

Question 16

Malignant tumours

Answer 16

spread through the body, invading & destroying other tissues & causes cancer

Question 17

metastasize

Answer 17

These tumours can break off the tumour, travel through the bloodstream, and may block the intestines, lungs or blood vessels