[3.7] mitosis

Question 1

what is the appearance of a chromosome during anaphase and telophase?

Answer 1

one sister chromatid with a centromere

Question 2

what is the appearance of a chromosome in prophase and metaphase?

Answer 2

2 sister chromatids joined at the centromere

Question 3

what do chromosomes contain?

Answer 3

DNA and histone proteins

Question 4

what is a sister chromatid?

Answer 4

genetically identical copies of half a chromosome resulting from DNA replication of a chromosome

Question 5

what is a diploid cell?

Answer 5

• when there are 2 copies of each chromosome (2n)
• they exist in pairs
• 23 pairs of chromosomes in humans

Question 6

what is a haploid cell?

Answer 6

• when there is only one copy of each chromosome (n)
• they exist individually
• humans have 23 individual chromosomes

Question 7

what are the 3 possibilities of cell division?

Answer 7

• 2n -> 2n (mitosis, humans, 2 daughter cells)
• n -> n (mitosis, fungi, 2 daughter cells)
• 2n -> n (meiosis, egg/sperm, 4 daughter cells)

Question 8

what are the 4 stages of mitosis?

Answer 8

1. prophase
2. metaphase
3. anaphase
4. telophase

Question 9

what happens during prophase?

Answer 9

• chromosomes have condensed and become visible
• nuclear envelope has (temporarily) broken down
• eg. 2 pairs of homologus chromosomes, same length, one coming from each parent

Question 10

what 2 new features are there in metaphase?

Answer 10

• centriole/MTOC
  > produces spindle fibres
• spindle fibres

Question 11

what happens during metaphse? (middle)

Answer 11

• chromosomes have aligned along the middle of the cell (at the equator)
• spindle fibres have attached to the chromosomes at the centromere
  > both fibres and centromere are proteins so they need to be complementary

Question 12

what happens during anaphase? (apart)

Answer 12

• sister chromatids are pulled to opposite poles of the cell by the spindle fibres

> this retraction requires lots of ATP released from respiration in mitochondria

Question 13

what happens during telophase?

Answer 13

• chromosomes have been pulled to opposite poles of the cell
• nuclear envelopes (membranes) have been reformed
• there is a full set of chromosomes (2 homologus pairs) at each part of the cell
• cell is now ready for cytokinesis

Question 14

what is the process of prokaryotic replication called?

not mitosis!

Answer 14

binary fission

Question 15

what happens during binary fission?

Answer 15

• before splitting occurs, the DNA needs to be replicated, as does any essential proteins, ribosomes, plasmids etc.
• binary fission is replication via splitting a single bacterial cell into two cells

Question 16

what is the genetics of the new cells produced in binary fission?

Answer 16

• genetically identical to each other and to the original ‘parent’ cell
  > they are not called daughter cells
• they will be genetically identical unless mutations occur

Question 17

how quickly can binary fission occur?

Answer 17

• under good conditions, binary fission can occur every 20 minutes
• 72 generations in a day
  > 4.7 × 10²¹?

Question 18

what happens during viral replication?

Answer 18

• it requires a host cell
• virus enters host cell
• viral DNA is inserted into host cell’s DNA
• viral DNA is then transcribed and translated along with the host cell’s DNA and it will also be replicated, along with the host cell’s DNA

Question 19

what is the outcome of viral replication?

Answer 19

• new viral DNA + new viral proteins produced by host cells
• viral DNA and viral proteins are new virus particles
  > DNA and capsid (made of protein) are the only key features of a virus