cell cycle and cancer

Question 1

what happens in the G1

Answer 1

• Cell grows to its normal size after division
• At the end of G1 the cell will have committed to dividing or not dividing

Question 2

what happens in S

Answer 2

Cells that have received a signal to divide progress to ‘s phase’
- DNA within the cell replicates
= each chromosome has 2 identical chromatids

Question 3

what happens in G2

Answer 3

• Cell continues to grow
• New DNA is checked
• Any errors are repaired
• Cell prepares for division
  (produces more tubulin to form microtubules for the spindle, centrosomes replicate)

Question 4

What is the order of mitosis

Answer 4

-PMAT, Prophase Metophase Anophase Telophase

Question 5

What happens in the Prophase

Answer 5

• Chromosomes condense and become visible
• Spindle fibers emerge from the centrosomes
• Nuclear envelope breaks down
• Nucleolus disappears

Question 6

What happens in metophase

Answer 6

• The chromosomes are seen to be made up of two chromatids.
• Each chromatid is identical copy of the DNA from the parent cell.
• The chromatids are joined by the centromere.
• Microtubules from the poles attach to the centromeres and the chromosomes arrange themselves across the equator of the cell.

Question 7

What happens in Anaphase

Answer 7

• In anaphase, the centromeres divide into two and the spindle fibres pull the individual chromatids making the chromosomes apart.
• The chromatids move to the opposite poles of the cell and now we refer to them as chromosomes.
• The energy for the process is provided by mitochondria.

Question 8

What happens in Telophase

Answer 8

-In this stage ,the chromosomes reach their respective poles and become longer and thinner, becoming chromatins.
-The spindle fibres disintegrate and the nuclear envelope and nucleolus re- form.

Question 9

what is cytokines in animal cells

Answer 9

-The cytoplasm divides in a process called cytokinesis.
The equator of the cell is constricted by a ring of actin microfilaments which contract (making the ring smaller and smaller) to produce a cleavage furrow which divides the cell and the membranes re-fuse.

Question 10

what is clevage furrow

Answer 10

-A cleavage furrow is an indecation that appears in a cell’s surface when the cell is preparing to divide.

Question 11

what are centromeres

Answer 11

-Structure in a chromosome that holds together the two chromatids

Question 12

what are microtubules

Answer 12

-Long protein fibers that extend from the centrioles in all possible directions, forming what is called a spindle. Some of the microtubules attach the poles to the chromosomes by connecting to protein complexes called kinetochores

Question 13

what are centrioles

Answer 13

-Centrioles are responsible for organizing the spindle fibers in the mitotic spindle apparatus and participate in the completion of cytokinesis

Question 14

what is the difference between malignant and benign tumour

Answer 14

-Benign : non cancerous, dont invade other tissues
-Malignant: cancerous, invade other tissues

Question 15

what is the normal function of Tumour Suppressor Gene and Proto-oncogene

Answer 15

• Tumour Suppressor Genes : Slow cell division Produce proteins that stop cells dividing or cause them to self- destruct

-Proto-oncogene : Stimulate cell division, Produce proteins to stimulate cell division

Question 16

what is oncogene

Answer 16

-Gene mutation causing the proto- oncogene to mutate into an oncogene.
-Oncogenes cause cancer cells to divide uncontrollably.

Question 17

How does the oncogene work?

Answer 17

-Cell receptors on the cell are permanently activated= switched on even in the absence of growth factors.
-This leads to excessive amounts of cell division being stimulated

Question 18

What do mutated TSG and proto-oncogene do

Answer 18

-TSG : can be inactivated therefore the proteins that stop cell dividing is not produced, cell devide uncontrollably

-Proto-oncogene : become overactive increasing the amount of proteins that stimulate cell devision