Terminology
- Synapsis
- Pairing of homologous chromosomes.
- Chiasmata
- Protein structures where recombination occurs.
- Tetrad Bivalent
- One pair of homologous chromosomes.
- Recombination
- Crossisng over of chismata.
- Recombinant
- The recombined chromatid.
- Non-Recombinant Parental-Type Chromosomes
- The non-recombined chromatid.
- Cohesion Protein Meiosis and Mitosis
- Keeps sister chromatids together.
-
- Separase protein Meiosis and Mitosis
- Separates them and degrades cohesion.
- Shugososhin Meiosis
- At centromere protects cohesion in anaphase I.
- Sister chromatids stay together until anaphase II.
- Psuedo-Autosomal Region PAR
- How XY chromosomes pair up???
- SRY Gene
- Male-determining gene.
- Can be caught up in recombination.
- Embryogenesis
- The development of the human embryo from the zygote.
Meiosis I
- Prophase I
- ?
- 5 phases:
-
- Leptotene
- ?
- Zygotene
- Synapsis occurs between Zygotene and Pachytene.
- Pachytene
- Tetrad (bivalent) forms w/ chiasmata between Pachytene amd Diplotene.
- Diplotene
- Female mammal eggs paused for up to 5 decades between Diplotene and Diakinesis = "dictyotene" or "dicyate" state.
- Diakinesis
- ?
- Metaphase I
- 50% chance of homologous chromosomes swapping sides = independent assortment.
-
- Total chance for a chromosomal configuration is humans is (1/2)^23.
- Anaphase I
- ?
- Telophase I
- ?
Meiosis I
- Cells are haploid, no homologous chromosomes.
- Prophase II
- ?
- Metaphase II
- Sister chromatids line up end to end along the metaphase plate.
- Anaphase II
- Sister chromatids pull apart.
- Telophase II
- ?
Possible Gametes
- Number of unique offspring possible.
2^n, where n is the number of heterozygous genes.
- 3 genes each:
AABBCc= 2^1 = 2 possible gametes.
AaBbCc = 2^3 = 8 possible gametes.