Mitosis

Question 1

Mitosis is important in the life of an organism. Give two reasons why.

Answer 1

1. Growth / increase in cell number;
2. Replace cells / repair tissue / organs /body;
3. Genetically identical cells;
4. Asexual reproduction /cloning;

Question 2

Describe the behaviour of chromosomes during mitosis and explain how this results in the production of two genetically identical cells. (7)

Answer 2

1 chromosomes shorten/thicken/supercoiling;
2 chromosomes (each) two identical chromatids/strands/copies
(due to replication);
3 chromosomes/chromatids move to equator/middle of the spindle/cell;
4 attach to individual spindle fibres;
5 spindle fibres contract / centromeres divide / repel;
6 (sister) chromatids/chromosomes (separate)
move to opposite poles/ends of the spindle;
7 each pole/end receives all genetic information/
identical copies of each chromosome;
8 nuclear envelope forms around each group of chromosomes/ chromatids/at each pole

Question 3

Describe what happens to the chromosomes during each of the following stages of mitosis. Prophase, Metaphase, Anaphase, Telophase.

Answer 3

prophase – coil up/spiralise/condense;
(allow shorter/contract/become visible)
metaphase – move to equator or centre of cell / attach to spindle;
(reject if reference to pairing)
anaphase – chromatids separate/centromeres divide;
(reject chromosomes move to poles without further explanation)
telophase – uncoil; (allow lengthen/becomes less visible)

Question 4

Describe two events which occur during interphase.

Answer 4

Increased in volume of cell / amount of cytoplasm / increase in mass /cell bigger;
Increase in number of organelles;
Protein synthesis / specific example;
DNA replication / chromosomes become chromatids / chromosomes copy;
I references to G1, G2 and S phases)
Increase in volume of cell/volume of cytoplasm / increase in mass / cell bigger; increase in number of organelles;
synthesis of protein/named protein;
DNA replication/increase / chromosomes copied;
ATP synthesis / respiration;