Cell Cycle

Question 1

What are the two types of nuclear division?

Answer 1

Mitosis
Meiosis

Question 2

What is chromatin?

Answer 2

More spread out form of DNA

Question 3

What is a chromosome?

Answer 3

A mor condensed form of DNA

Question 4

What’s a centromere?

Answer 4

Attaches two genetically identical molecules made from DNA replication

Question 5

What is a centriole?

Answer 5

Small hollow cylinders which form centrosomes

Question 6

What are centrosomes?

Answer 6

2 hollow cylinders orientated at right angles to one another and form a network of microtubules/filaments (spindle fibres)

Question 7

What are the three main stages of the cell cycle?

Answer 7

Interphase
Mitosis
Cytokinesis

Question 8

What are the three stages of interphase?

Answer 8

G1
S
G2

Question 9

What happens during the G1 stage of interphase?

Answer 9

• Growth of cell
• Duplication of organelles
• Protein Synthesis

Question 10

What happens during the S stage of interphase?

Answer 10

DNA replication

Question 11

What happens during the G2 stage of interphase?

Answer 11

• More growth
• Checking for errors in replicated DNA

Question 12

What are the 4 stages of Mitosis?

Answer 12

• Prophase
• Metaphase
• Anaphase
• Telophase

Question 13

What happens during PROPHASE of mitosis?

Answer 13

• The nuclear envelope disintergrates
• The nucleolus disappears
• Chromatin condenses (shortens/thickens) to form chromosomes
• Centrioles move to opposite poles of the cell
• Spindle fibres (microtubules) start to develop

Question 14

What happens during the METAPHASE stage of mitosis?

Answer 14

• Chromosomes line up along the equator (in the middle of the cell)
• Attached to the spindle fibres by their centromeres

Question 15

What happens during the ANAPHASE stage of mitosis?

Answer 15

• Spindle fibres contract and shorten pulling sister chromatids apart and to opposite poles of the cell
• Centromeres divide in two separating each pair of sister chromatids
• This appears V-Shaped

Question 16

What happens during the TELOPHASE stage of mitosis?

Answer 16

• Chromatids reach opposite poles on spindle fibres - called chromosomes
• Chromosomes decondenses to reform chromatin
• Spindle fibres disintegrate
• Nuclear envelope reforms around each group of chromosomes
• Nucleolus reappears
• Clevage furrows form to begin cytokinesis

Question 17

What is a clevage furrow?

Answer 17

When the cell pinches together to perform cytokinesis

Question 18

What is cytokinesis?

Answer 18

The cytoplasm splits/divides to form 2 genetically identical daughter cells

Question 19

Why is only the root tip used when calculating a mitotic index?

Answer 19

• They have meristem cells at the root tip which are actively undergoing mitosis
• Cells further up from the root tip are elongating but not dividing

Question 20

How do prokaryotic cells divide?

Answer 20

Binary Fiisoon

Question 21

Describe the process of Binary Fission?

Answer 21

• Cell replicates it’s circular DNA and plasmids
• The cell elongates and grows separating the DNA loops to opposite ends of the cell
• Cross walls form so membrane invaginate (fold in) and the cytoplasm divides
• Forms two daughter cells

Question 22

Why do we use Logs when working out bacteria cell growth ?

Answer 22

It helps us to compare data with a large range of values more accurately

Question 23

What type of process is mitosis?

Answer 23

It’s a GENE CONTROLLED process

Question 24

What are the two types of genes which control mitosis?

Answer 24

Oncogenes
Tumour Suppressor Genes

Question 25

What do Proto - Oncogenes do when switched on?

Answer 25

Cause cell to divide

Question 26

If the Proto - Oncogenes mutates to an Oncogene what happens?

Answer 26

The oncogene becomes permanently switched on leasing to uncontrolled cell division

Question 27

What is a TS gene?

Answer 27

Tumour Suppressor gene

Question 28

What is the function of TS genes?

Answer 28

Slows down cell division (helps maintain normal rates of cell division)

Question 29

What will happen is a mutation of the TS gene occurs?

Answer 29

Leads to uncontrolled cell division and tumour growth

Question 30

What are cancer treatments directed at?

Answer 30

Controlling the rate of cell division by killing rapidly dividing cells through blocking parts of the cell cycle

Question 31

How does chemotherapy control rapidly dividing cells?

Answer 31

- Prevents DNA replication - Inhibits metaphase by preventing spindle fibres forming - Inhibits nucleotide synthesis

Question 32

What is the problem with cancer treatments like chemotherapy?

Answer 32

It can interfere with with the cell cycle of normal cells which divide rapidly (causing damage) For example hair producing cells = Hair loss

Question 33

How do you calculate mitotic index?

Answer 33

Number of cells in mitosis (visible chromosomes) / total number of cells

Question 34

Explain how there came to be two copies of each allele of each gene at this stage of meiosis.

Answer 34

DNA is each chromosome has been replicated to give two chromatids - so two copies of gene/allele, one on each chromatid