[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 homologous pair of chromosomes?

Answer 5

two chromosomes that carry the same genes

Question 6

what is a diploid cell?

Answer 6

• have 2 copies of each chromosome (pairs)
• 23 pairs of chromosomes in humans

Question 7

what is a haploid cell?

Answer 7

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

Question 8

what are the 3 possibilities of cell division?

Answer 8

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

Question 9

what are the 4 stages of mitosis?

Answer 9

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

Question 10

what happens during prophase?

Answer 10

• chromosomes condense and become visible
• nuclear envelope is temporarily broken down
• spindle fibres form

Question 11

what 2 new features are there in metaphase?

Answer 11

• centriole/MTOC
  > produces spindle fibres
• spindle fibres

Question 12

what happens during metaphse? (middle)

Answer 12

• chromosomes align along equator of cell
• spindle fibres attach to chromosomes at centromere

fibres and centromere are proteins so need to be complementary

Question 13

what happens during anaphase? (apart)

Answer 13

• 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 14

what happens during telophase?

Answer 14

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

Question 15

what is the process of prokaryotic replication called?

not mitosis!

Answer 15

binary fission

Question 16

what happens during binary fission?

Answer 16

• 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 17

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

Answer 17

• 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 18

how quickly can binary fission occur?

Answer 18

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

Question 19

what happens during viral replication?

Answer 19

• 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 20

what is the outcome of viral replication?

Answer 20

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