Cycle 4 - Meiosis Flashcards
Explain the basic mechanism of DNA recombination in prophase I of meiosis
Synaptonemal complex: As the homologous chromosomes pair, they are held together tightly by a protein framework called the synaptonemal complex
Cohesin: holds sister chromatids together
**undergo synapsis then cross over at the chaismata**
Recombination arranges alleles into novel combinations by chance.
How do homologous chromosomes pair up?
Homologues pair front to back (not side by side) in order for all non-sister chromatids to be close enough to each other to participate in recombination.
The closer that two alleles are, the more likely they are to be inherited together and thus have a stronger genetic linkage
Explain the animal life cycle
Explain the plant life cycle
Explain the fungi/algae life cycle
Describe the characteristics of homologous chromosomes
Chromosome pairs of approximately the same:
- Length
- Centromere position
- Staining pattern for genes with the same corresponding loci.
Why is meiosis I called reductional and meisosi II called equational?
Meiosis I / Reductional (as the ploidy is halved)
Meiosis II / Equational (as the haploids divide)
Explain the changes in n and C during human meiosis
Pre-S phase: 2n 2C (standard diploid tissue)
Meiosis I: 2n 4C
Meiosis II: 1n 2C
Final: 1n 1C
Describe a way in which meiosis can be thought of as a kind of DNA “repair”
When the homologues pair during synapsis in prophase of meiosis, recombination events between the two mutations can yield non-mutated chromatids
Explain the result of failure to separate in meiosis
Results in changes in the number of entire chromosomes, leading to aneuploidy (having an extra or missing chromosome, ex 45 or 46 total) or polyploidy = one or more extra)
Failure to separate
- Meiosis I: nondisjunction
- Meiosis II: misdivision
