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BIO - 2.1.6 Cell Division > Meiosis purpose > Flashcards

Flashcards in Meiosis purpose Deck (5)
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- Normal cells have 2 chromosomes of each type so they are DIPLOID.
- In sexual reproduction 2 gametes fuse to produce a fertilised egg (zygote).
- Zygote is the origin of all cells that an organism develops.
- Gametes are HAPLOID as they contain half the standard no. of chromosomes.
- Gametes are produced by meiosis as 4 daughter cells are made.
- Meiosis is known as reduction division.


Homologous chromosomes

- Each characteristic of an organism is coded for by 2 copies of each gene.
- Each nucleus contains a pair of genes for each characteristic.
- So they have 2 full sets of genes.
- Therefore each nucleus contains matching sets of chromosomes called homologous chromosomes.
- Each chromosome in a homologous pair has the same genes at the same position of chromosome.


What are alleles?

Different versions of the same gene.
Different alleles of a gene will all have the same locus.


Crossing over of chromatids

- During prophase 1, homologous pairs of chromosomes come together and pair up.
- Chromatids twist around each other and bits of chromatids swap over.
- Chromatids still contain same genes but different combo of alleles.


Independent assortment

- When homologous pairs line up in metaphase 1 and are separated in anaphase 1, it's completely random which chromosome from each pair ends up in which daughter cell.
- So the 4 daughter cells produced have completely different combinations of maternal and paternal chromosomes.