Meiosis Flashcards
What does meiosis do
Produces cells which are haploid for sexual reproduction (gametes)
Prophase I
- chromosomes form bivalents (pairs of homologous chromosomes)
- arms of chromatids may cross over to form chiasmata. Genetic material can be exchanged between chromosomes and increase genetic variation
Describe crossing over
Arms of chromatids cross over each other, forming chiasmata. Genetic material can be exchanged between homologous chromosomes. This increases genetic variation
Metaphase I
• homologous chromosomes arrange themselves in pairs along equator.
• random assortment occurs. Homologous chromosomes from both parents arrange themselves randomly along spindle, facing each pole
Describe random assortment
Homologous chromosomes from both parents arrange themselves randomly along the spindle facing each pole
Anaphase I
Chromosome bivalents separate as each chromosome is pulled by its centromere (doesn’t split) towards opposite poles
Telophase I
• nuclear envelope reforms around the chromosomes at the poles.
• as the chromosome pairs have separated, chromosomes are no linger in lairs and the cells are haploid
Prophase, metaphase, anaphase and telphase II
Events occur in each new nucleus exactly like in mitosis. Then cytokinesis occurs to create 4 genetically varied cells
Compare mitosis and meiosis
• 1 nuclear division in Mitosis, 2 in meiosis.
• 2 daughter cells in Mitosis, 4 in meiosis.
• genetically identical cells in mitosis, genetically different in meiosis.
• no pairing of homologous chromosomes in mitosis, is in meiosis to form bivalents.
Can haploid cells divide by meiosis?
No, only mitosis