Mitosis

Question 1

Why is mitosis so important

Answer 1

• mitosis is the nuclear division of cell cycle
• it ensures both daughter cells are genetically identical to the parent cell
• it is essential for when all the daughter cells have to be the same eg for growth, repairing tissues
• it’s also necessary for asexual reproduction which is the production of genetically identical offspring from one parent in multicellular organisms

Question 2

Give a brief description of what happens to the chromosomes before mitosis can begin

Answer 2

• each DNA molecule (chromosome) is converted into two identical DNA molecules called chromatids
• 2 chromatids are joined at the centromere

Question 3

Describe prophase in mitosis

Answer 3

• chromatin fibres begin to coil and condense to form chromosomes, the nucleolus disappears and the nuclear envelope begins to break down
• protein microtubules form spindle shaped structures linking the poles of the cell, the fibres are responsible for moving chromosomes into correct position
• centrioles move to the poles of the cell to aid in the formation of the spindle
• spindle fibres attach to the centromere and move the chromosomes to the centre of the cell

Question 4

Describe Metaphase

Answer 4

• during metaphase the chromosomes are moved by the spindle fibres to line up on he equator of the cell to form a plane
• called the metaphase plate

Question 5

Describe anaphase

Answer 5

-the centromeres holding the chromatids together divide during anaphase
- the chromatids are separated, pulled to the opposite poles of the cell by shortening spindle fibres
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Question 6

Describe Telophase

Answer 6

• the chromatids reach the poles of the cell and form chromosomes
• the nuclear envelope begins to form around them
• the chromosomes start to uncoil and the nucleolus is formed
• cytokinesis begins

Question 7

Describe Cytokinesis in animal and plant cells

Answer 7

• in animal cells a cleavage furrow forms in the middle of the cell
• the cell surface membrane is pulled inwards by the cytoskeleton until it is close enough to fuse around the middle forming 2 cells
• in plants this can’t happen due to cell wall, vesicles from the Golgi assemble along the equator and fuse to each other and the cell surface membrane, dividing the cell into 2