- Define mitosis as the nuclear division giving rise to genetically identical cells (details of stages are not required)
Learn the definition!
- State that the exact duplication of chromosomes occurs before mitosis
Before mitosis occurs, all the chromosomes in the cells are exactly duplicated. This is because, in mitosis, all the nuclei divide into 2 separate nuclei, taking half the chromosomes each.
Having duplicates means that each daughter nucleus will possess the full set of chromosomes (in humans, each daughter nucleus will possess the full 23 chromosomes).
- State the role of mitosis in growth, repair of damaged tissues, replacement of cells and asexual reproduction
Since mitosis gives rise to genetically identical daughter cells, mitosis is useful when we need more of the same type of cells for example:
In growth, body cells divide to form more of the same type of body cells e.g. hair cells divide to produce more hair cells, etc.
This is also important when repairing damaged tissue. For example, imagine you cut yourself. You have damaged your skin tissue, so now you need more skin cells to patch up the wound, and thus, mitosis is useful.
Mitosis is useful in replacement of worn-out cells for obvious reasons too.
Asexual reproduction relies on mitosis too, because this type of reproduction does not rely on the fusion of gamete nuclei, so mitosis ensures that the chromosome number is maintained.
- Define mitosis as reduction division in which the chromosome number is halved from diploid to haploid resulting in genetically different cells (details of stages are not required)
Memorise the definition!
Note: Meiosis results in genetic variation so the cells produced are not all genetically identical.
Let me explain.
We already know that each diploid cell has two sets of chromosomes, right? So each corresponding chromosome has the same genes in the same order, but the alleles of each gene might be different. This means that when meiosis occurs, and the chromosomes are split between the daughter cells, some daughter cells will get one of the alleles and the other daughter cells will get the other allele. Therefore, the daughter cells are not genetically identical and there is genetic variation.
- State that meiosis is involved in the production of gametes
Gametes are a result of meiosis – meiosis means that the diploid parent cells can give rise to haploid gametes.
Notes submitted by Sarah
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