Meiosis Flashcards
External fertilisation
Animals release their gametes into the external environment. Fertilisation occurs outside the organism’s body.
Internal fertilisation
Animals who deliever gametes directly into the reproductive tract. The fertilisation occurs in the body.
Prophase 1
The chromosomes begin to condense, but they also pair up, called homologous chromosomes.
Homologous chromosomes trade parts, this is called crossing over, where they exchange genetic information.
Metaphase 1
Homologue pairs - not individual chromosomes - line up at the metaphase plate for separation.
Anaphase I
The homologue chromosome pair is pulled apart from the other pair and move apart to opposite ends of the cell.
The sister chromatids of each chromosome, however, remain attached to one another and don’t come apart.
Telophase 1
The chromosomes arrive at opposite poles of the cell.
Cytokinesis usually occurs at the same time as telophase 1, forming two haploid daughter cells.
Prophase 2
Chromosomes condense and the nuclear envelope breaks down.
Spindle fibres form and begin to attach to chromosomes.
NO CROSSING OVER OCCURS
Metaphase II
The chromosomes line up individually along the metaphase plate.
Anaphase II
The sister chromatids seperate and are pulled towards opposite poles of the cell.
Telophase II
Nuclear membranes form around each set of chromosomes, and the chromatids uncoil
Cytokinesis
Splits the chromosome sets into new cells, forming the final products meiosis.
Final product of meiosis
Four haploid cells, that are NON IDENTICAL to each other where each chromosome has just one chromatid.
