Cells: Cell cycle and mitosis

Question 1

Name the three MAIN stages in the cell cycle

Answer 1

• Interphase
• Mitosis
• Cytokinesis

Question 2

Name the three stages of interphase

Answer 2

• G1 phase
• S phase
• G2 phase

Question 3

What occurs during the G1 phase

Answer 3

Cell is growing then receives a signal to divide

Question 4

What occurs during the S phase

Answer 4

DNA replicates

Question 5

What occurs during the G2 phase

Answer 5

• Synthesis of various proteins occurs (ribosomes, microtubules)
• Checkpoint where DNA is proof-read

Question 6

How many chromosomes do humans have in their body cells

Answer 6

46

Question 7

Name and describe the features of a chromosome

Answer 7

Centromere - region where the cells’ spindle fibres attach (centre of the chromosome)
Chromatid - one of the two identical halves of a chromosome
Sister chromatids - Identical copies of a single chromosome

Question 8

What is mitosis

Answer 8

• The process of nuclear division by which two genetically identical daughter nuclei are produced that are also genetically identical to the parent cell nucleus

Question 9

Name the stages of mitosis in order

Answer 9

• Prophase
• Metaphase
• Anaphase
• Telophase

Question 10

Name all the stages in the cell cycle in order

Answer 10

• Interphase (G1, S , G2)
• Prophase
• Metaphase
• Anaphase
• Telophase
• Cytokinesis

Question 11

State the main events of each stage of mitosis

Answer 11

• Prophase - Chromosomes condense
• Metaphase - Chromosomes line up in them middle of the cell
• Anaphase - Chromatids break apart at he centromere and move to opposite poles
• Telophase - Two nuclei form after nuclear envelopes reform around each group of chromosomes

Question 12

What happens during prophase

Answer 12

• Chromosomes condense and are now visible when stained
• The two centrosomes (replicated in the G2 phase just before prophase) move towards opposite poles of the cell
• Spindle fibres begin to emerge from the centrosomes
• The nuclear envelope (nuclear membrane) breaks down into small vesicles

Question 13

What happens during metaphase

Answer 13

• Centrosomes reach opposite poles
• Spindle fibres continue to extend from centrosomes
• Chromosomes line up at the equator of the spindle
• Spindle fibres reach the chromosomes and attach to the centromeres
• Each sister chromatid is attached to a spindle fibre

Question 14

What happens during anaphase

Answer 14

• The sister chromatids separate at the centromere
• Spindle fibres begin to shorten
• The separated sister chromatids are pulled to opposite poles by the spindle fibres

Question 15

What happens during Telophase

Answer 15

• Chromosomes arrive at opposite poles and begin to decondense
• Nuclear envelopes begin to reform around each set of chromosomes
• The spindle fibres break down

Question 16

What happens during cytokinesis in animal cells

Answer 16

A cleavage furrow forms and separates the daughter cells

Question 17

What happens during cytokinesis in plant cells

Answer 17

• A ‘cell plate’ forms at the site of the metaphase plate
• Once the cell plate reaches the cell walls of the parent cell, new cell walls are produced, separating the new daughter cells

Question 18

Why is mitosis needed

Answer 18

To grow and repair body cells

Question 19

What occurs during interphase

Answer 19

• Cell receives a signal to divide
• DNA replicates
• Synthesis of various proteins occurs (ribosomes, microtubules)
• Checkpoint where DNA is proof-read
• ATP content increases

Question 20

How are tumours formed

Answer 20

When cells develop mutations that make them divide uncontrollably

Question 21

How can a cancer treatment target the cell cycle

Answer 21

• G1 (cell growth and protein production): Some chemical drugs (chemotherapy) prevent the synthesis of enzymes needed for DNA replication
  
  • If these aren’t produced, the cell is unable to enter the synthesis phase (S), disrupting the cell cycle and forcing the cell to kill itself
• S phase (DNA replication): Radiation and some drugs damage DNA. At several points in the cell cycle (including just before and during S phase) the DNA in the cell is checked for damage
  – If severe damage is detected, the cell will kill itself, preventing further tumour growth

Question 22

State the main event that occurs during prophase

Answer 22

Chromosomes condense

Question 23

State the main event that occurs during metaphase

Answer 23

Chromosomes line up in them middle of the cell

Question 24

State the main event that occurs during anaphase

Answer 24

Chromatids break apart at he centromere and move to opposite poles

Question 25

State the main event that occurs during telophase

Answer 25

Two nuclei form after nuclear envelopes reform around each group of chromosomes

Question 26

What is a cleave furrow

Answer 26

An indentation that appears in a cell’s surface when the cell is preparing to divide

Question 27

What is a metaphase plate

Answer 27

An imaginary plane axis that lies between the centrosomes at different poles of the cell

Question 27

What is a cell plate

Answer 27

A structure that forms when the cytoplasm of a plant cell divides