Cell Division (D)

Question 1

What is the cell cycle?

Answer 1

A regulated process that occurs, resulting in division of a parent cell into 2 identical daughter cells, this includes interphase and mitosis

Question 2

What happens in the 1st stage of the cell cycle?

Answer 2

GAP 1 (G1)
The cell prepares for replication and grows in size

Question 3

What happens in the 2nd stage of the cell cycle?

Answer 3

SYNTHESIS
DNA is replicated

Question 4

What happens in the 3rd stage of the cell cycle?

Answer 4

GAP 2
Additional growth and synthesis of proteins needed for mitosis

Question 5

What happens in prophase?

Answer 5

PROPHASE (prep)
- Nuclear envelope is broken down
- Chromosomes condense
- Spindle fibres begin to form from centrioles

Question 6

What happens in metaphase?

Answer 6

METAPHASE (middle)
- Chromosomes line up at the equator of the cell,
- Attached to the spindle fibres by the centromeres
- Spindle fibres continue to expand

Question 7

What happens in anaphase?

Answer 7

ANAPHASE (apart)
- Sister chromatids pulled to opposite poles from the centromere (chromatids are now called chromosomes) by the spindle fibres

Question 8

What happens in telophase?

Answer 8

TELOPHASE (2 nuclei)
- Chromosomes decondense
- Nuclear envelope is formed again
- Spindle fibres break down
- 2 nuclei formed

Question 9

What happens in cytokinesis?

Answer 9

CYTOKINESIS (breaKINg)
- Cell membrane pinches into 2 new genetically-identical cells
- Cytoplasm separates

Question 10

What are the uses of mitosis

Answer 10

1) Growth - zygotes can become multicellular organisms through mitosis
2) Cell replacement - damaged tissue can be replaced by mitosis, dead cells are replaced with clone daughter cells
3) Asexual reproduction - some organisms produce genetically identical offspring through mitosis

Question 11

What 2 mechanisms allow meiosis to produce genetic variation in offspring?

Answer 11

Crossing over and independent assortment

Question 12

What is crossing over?

Answer 12

• A homologous pair of chromosomes line up (this is a bivalent)
• Non sister chromatids cross over at crossing points called chiasmata
• A section of chromatid from each chromosome breaks off and rejoins with the chromatid of the other chromosome

Question 13

What is the result of crossing over?

Answer 13

It produces variation because the swapping of the SAME genes with DIFFERENT alleles resulting in a new combination of alleles on both chromosomes

Question 14

What is independent assortment?

Answer 14

The random alignment of homologous pairs at the equator leads to different genetic combinations in the daughter cells
The homologous chromosomes are then pulled apart at centrioles to form 2 new cells with varied chromosomes and genes with different alleles

Question 15

Why is genetic variation important?

Answer 15

Offspring have better survival rate in changing conditions
Protection against pathogens/diseases due to varied alleles