Eukaryotic Cell cycle and Division (brief)

Question 1

What are the three stages in cell division

Answer 1

• Interphase
  -Mitosis
• Cytokenesis

Question 2

What does the cell cycle ultimately result in ?

Answer 2

The formation of two new identical daughter cells

Question 3

What is interphase split into ?

Answer 3

G1, S , G2

Question 4

Describe what happens in G1

Answer 4

• Cell absorbs material, grows and develops. Protein synthesis also happens in this phase

Question 5

What happens in S?

Answer 5

-Protein synthesis occurs and chromosomes replicate via semi conservative replication

Question 6

What happens in G2

Answer 6

Time where organelles and other materials needed for cell division are synthesised

Question 7

What happens in mitosis ?>

Answer 7

• The stage where cells are actively dividing

Question 8

Describe cytokenesis

Answer 8

Final stage of cell division where the cell membrane divides and the new cells seperate

Question 9

What do the chromosomes appear as during interphase ?

Answer 9

• Chromatin, loose open structure so the DNA is available for DNA rep

Question 10

What joins two sister chromatids ?

Answer 10

• Centromere

Question 11

What happends during Prophase ?

Answer 11

• Chromosomes coil and condense and DNA becomes visible
• Nuclear membrane starts do break down
• Centrioles move to opposite poles of the cell and form proteins which attach to the centromere of each chromosome.

Question 12

What happens during metaphase

Answer 12

• Chromosomes align along the equator of the cell.
• Spindle apparatus fully forms

Question 13

What happens during anaphase ?

Answer 13

• Centromeres divide into two and spindle fibres start to shorten
• ## This pulls the sister chromatids to opposite poles of the cell

Question 14

Describe what happens in telophase

Answer 14

• Spindle apparatus breaks down and nuclear membranes reform
• Chromosomes uncoil back to chromatin state

Question 15

What happens during Cytokenesis

Answer 15

• Central cell membrane pulled inwards via the cytoskeleton, this this causes a groove.
• Eventually membranes fuse to form two independent cells

Question 16

What are two roles of the cell cycle

Answer 16

• Growth and repair
• Asexual reproduction

Question 17

Where does cell division by meiosis take place ?

Answer 17

• Sex organs of organisms

Question 18

What does cell division by meiosis produce

Answer 18

• Gametes

Question 19

Why is it important that meiosis produces haploid gametes ?

Answer 19

• Because during fertilisation, two haploid cells fuse to form a diploid zygote

Question 20

What are two ways that genetic variation is introduced in meiosis ?

Answer 20

• Crossing over
• Independent assortment

Question 21

Explain crossing over

Answer 21

• During prophase 1, the non sister chromatids of homologous chromosomes twist around each other causing tensions
• During the tensions the chromatids break off at the chiasma
• The broken parts of the non sister chromatids rejoin on the other chromosome of the homologous pair
• This arises genetic variation

Question 22

Describe independent assortment

Answer 22

• Chromosomes which come from both parents are randomly distributed randomly in the parents
• Each gamete receives 23 chromosomes
• In each new gamete you could receive none to all 23 chromosomes from either maternal or paternal chromosomes

Question 23

Explain the importance of meiosis in the production of gametes

Answer 23

• Halves the number of chromosomes to produce a haploid nucleus
• So then at fertilisation the full diploid number of chromosomes are restored
• It also allows genetic variation in organisms via independent assortment and crossing over