2: CELLS - CELL DIVISION

Question 1

What are the 4 stages of the cell cycle?

Answer 1

• G1 (gap phase 1)
• S (synthesis)
• G2 (gap phase 2)
• mitosis

Question 2

Which stages of the cell cycle are part of interphase?

Answer 2

• G1
• S
• G2

Question 3

What happens during interphase?

Answer 3

• cell carries out normal functions but also prepares to divide
• DNA unravelled and replicated
• organelles replicated
• ATP content increased (provides energy needed for cell division)

Question 4

What is the structure of chromosomes after replication?

Answer 4

made of 2 strands (sister chromatids) joined in the middle by a centromere (when mitosis is complete, the chromatids end up as 1 strand chromosomes in the new daughter cells)

Question 5

What are the 4 stages of mitosis?

Answer 5

• prophase
• metaphase
• anaphase
• telophase

Question 6

What happens during prophase?

Answer 6

• chromosomes condense becoming shorter and fatter
• centrioles start moving to opposite poles of the cell forming spindle fibres across the cell
• nuclear envelope breaks down and chromosomes lie free in the cytoplasm

Question 7

What happens during metaphase?

Answer 7

chromosomes line up along the centre of the cell and become attached to the spindle by their centromere

Question 8

What happens during anaphase?

Answer 8

• centromeres divide, separating each pair of sister chromatids
• spindles contract, pulling chromatids to opposite poles of the cell, centromere first

Question 9

What happens during telophase?

Answer 9

• chromatids reach opposite poles of the cell and uncoil to become long and thin again
• nuclear envelope forms around each group of chromosomes

Question 10

What happens during cytokinesis?

Answer 10

• cytoplasm splits
• 2 genetically identical cells produced

Question 11

What are proto-oncogenes?

Answer 11

the genes that regulate cell division

Question 12

What would happen if a mutation were to occur in the proto-oncogenes?

Answer 12

cells would divide uncontrollably

Question 13

What is cancer?

Answer 13

• a condition where cells in a specific part of the body reproduce uncontrollably
• mutation in a gene that controls cell division can cause cells to divide rapidly and become out of control
• cells keep dividing to make more and more cells which form a tumor
• cancerous tumours invade surrounding tissue

Question 14

What is a malignant tumor?

Answer 14

a mass of cells that invades other tissues and is capable of producing metastases

Question 15

What is metastasis?

Answer 15

• mutated tumor cells break off and are transported via the bloodstream to other organs and tissues
• these cells then invade tissues and develop into secondary tumors

Question 16

What is apoptosis?

Answer 16

• process of programmed cell death (once your organs have grown to full size and you stop growing most cells lose their ability to divide)

Question 17

What are cancer treatments designed to do?

Answer 17

control rate of cell division in tumour cells by disrupting cell cycle which kills tumour cells

Question 18

How do cancer treatments that target the G1 stage work?

Answer 18

• chemical drugs prevent synthesis of enzymes needed for DNA replication
• if these enzymes aren’t produced cell is unable to enter S stage which disrupts the cell cycle forcing the cell to kill itself preventing further tumour growth

Question 19

How do cancer treatments that target the S stage work?

Answer 19

• radiation and some drugs damage DNA
• at several points in cell cycle DNA is checked for damage. if severe damage is detected the cell will kill itself preventing further tumour growth