Genetic Code & Cell Function
- Created by: beth-marie2511
- Created on: 18-06-16 22:46
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- Genetic Code & Cell Function - Meiosis 1
- Prophase 1
- Chromosomes shorten and thicken (condense) to form visible chromatids
- Centrioles move to the opposite poles and form microtubules
- Spindle fibres begin to form
- Homologous chromosomes pair up and form homologous bivalents
- Each bivalent has 4 strands made up of two chromosomes each
- Chromatids 'cross over' at certain points, where the chromatids break and exchange DNA
- Chiasmata / Crossing over
- Creates genetic variation
- Nucleolus disappears and nuclear envelope breaks down
- Metaphase 1
- Homologous bivalents align themselves along the equator of the spindle
- Maternal and paternal chromosomes are arranged randomly
- Random Assortment
- This leads to further genetic variation
- Anaphase 1
- Homologous bivalents separate
- One of each pair is pulled to the opposite poles
- Each pole receives only one of each homologous bivalent
- As the spindle fibres contract
- There is a mixture of maternal and paternal chromosomes
- Telophase 1
- Chromosomes remain in their condensed form
- Cytokinesis
- Cytoplasm splits and forms 2 haploid cells
- Nuclear envelope reforms around the haploid chromosomes
- Spindle disappears
- Prophase 1
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