11.3 Process of meiosis Flashcards
1
Q
Prophase I of meiosis
A
- homologous chromosomes become closely associated in synapsis
- exchange segments by crossing over
- then separate
2
Q
Prophase I
A
- chromosomes condense, spindle of microtubules form
- DNA has been replicated
- two sister chromatids attach at centromere
- crossing over occurs
3
Q
Metaphase I
A
- pairs of homologous chromosomes align on metaphase plate
- microtubules from opposite poles attach to kinetochores of each homologue
4
Q
Anaphase I
A
- kinetochore microtubules shorten
- homologous pairs pulled apart
- sister chromatids do not separate as they do in mitosis
5
Q
Telophase I
A
- separated homologues form cluster at each pole of cell
- nuclear envelope reforms
6
Q
cytokinesis in meiosis
A
- resulting two cells have half number of chromosomes as original
- ex: each nucleus contains two chromosomes ( four in original cell)
7
Q
Why are the two sister chromatids not identical?
A
-because crossing over has occurred
8
Q
Prophase II
A
- follows brief interphase with no S phase
- new spindle apparatus forms in each cell
- nuclear envelop breaks down
9
Q
Metaphase II
A
- chromosomes consisting of sister chromatids joined at centromere (along metaphase plate)
- kinetochore microtubules attach to kinetochores of sister chromatid( as it does in mitosis)
10
Q
Anaphase II
A
- microtubules shorten
- sister chromatids pull to opposite poles (as in mitosis)
11
Q
Telophase II
A
- nuclear membranes re-form around four chromosomes
- after cytokinesis, four haploid cells result
12
Q
Why are no cells alike in meiosis?
A
- random alignment of homologous pairs at metaphase I
- crossing over during prophase I
