10.3: Meiosis reduces the number of chromosomes sets from diploid to haploid Flashcards
What needs to happen before meiosis?
interphase (duplication of cells)
What comes after the duplication?
this duplication is followed by 2 divisions (meiosis 1 and 2)
What does meiosis result in?
results in 4 genetically different daughter cells
How do the chromosomes in the cell compare?
the 2 chromosomes seem to be the same in size (homologous, but they both have different alleles
Prophase 1
spindle fibers form, nuclear envelope breakdown occurs, chromosomes condense, Crossing over and Synapsis occurs
crossing over
when homologous pairs bind alongside each other, DNA of non-sister chromatids are joined to each other, exchange segments
chiasmata
where the crossovers occur
Metaphase 1
4 chromosomes(tetrads) align at the metaphase plate, microtubules attach
Anaphase 1
split apart, 2 chromatids on each side
Telophase 1 and Cytokinesis
each half of the dividing cell has a haploid set, in cytokinesis the cytoplasm is split and 2 cells form, remember a cleavage furrow
Compare Meiosis 1 and 2
same as Meiosis 1 but crossing over doesn’t happen, duplication doesn’t happen
nuclei appear here
Each of the 4 cells is genetically distinct (are haploid)
What phase do most things happen
Prophase 1 is where most things are happening
synaptonemal complex
zipper-like structure between the 2 chromosomes (nonsister)
synapsis
DNA breaks are close up so both chromatids are attached
Key difference between meiosis and mitosis?(4)
- key differences include reduction of chromosomes in meiosis and not being the same as the parent cell
- Synapsis and crossing over. Pairing and crossing over does not occur in mitosis
- Alignment of homologous chromosomes at the metaphase plate: pairs of chromosomes are at the plate unlike individual chromosomes
- Separation of homologs: sister chromatids remain attached in anaphase
