Meiosis in detail -- Lecture 9 Flashcards
phases of meiosis:
interphase (G1, S, G2)
meiosis I (reduction division)
interkinesis (a rest period)
meiosis II
phases of meiosis:
after interphase…
1 diploid cell (2 chromatids/chromosome)
phases of meiosis:
after meiosis I…
2 haploid cells (2 chromatids/chromosome)
homologous chromosomes are segregated
phases of meiosis:
after meiosis II…
4 haploid cells (1 chromatid/chromosome)
sister chromatids are segregated
prophase 1 events:
1) chromosomes condense
2) nuclear membrane breaks down
3) spindle poles begin to form
4) homologous chromosomes pair up and are held together by synaptonemal complex proteins –> form a complex called a bivalent or tetrad
crossing over during meiosis 1:
crossing over: in a ___, genetic material can be exchanged b/n paired chromosomes
bivalent
crossing over during meiosis 1:
crossing over: in a bivalent, ___ can be exchanged b/n paired chromosomes
genetic material
crossing over during meiosis 1:
crossing over: in a bivalent, genetic material can be ___ b/n paired chromosomes
exchanged
crossing over during meiosis 1:
crossing over: in a bivalent, genetic material can be exchanged b/n ___
paired chromosomes
crossing over during meiosis 1:
crossing over rearranges chromosomes and increases ___
genetic variation
crossing over during meiosis 1:
may occur ___ times along chromosomes
multiple
crossing over during meiosis 1:
only occurs during ___ when homologs are paired
prophase 1
crossing over during meiosis 1:
only occurs during prophase 1 when ___ are paired
homologs
crossing over during meiosis 1:
only occurs during prophase 1 when homologs are ___
paired
metaphase 1:
homologous pairs line up at metaphase plate
metaphase 1:
alignment of homologs on either side of the metaphase plate is ___
random
metaphase 1:
independent assortment (what does it do)
ensures each new cell contains a mixture of homologs from the mother and father –> leads to greater genetic diversity
anaphase 1:
events
synaptonemal complex proteins dissolve
homologs separate
homologs are segregated to opposite spindle poles by kinetochore microtubules
anaphase 1:
homologs are segregated to opposite spindle poles by ___
kinetochore microtubules
telophase 1:
events
chromosomes begin to decondense
spindle network breaks down
nuclear membranes re-form
during/after telophase 1:
cytokinesis…
meiosis 1…
interkinesis…
cytokinesis divides the cell
meiosis 1 is completed
interkinesis occurs
interkinesis (definition)
period of rest after meiosis 1 in preparation for meiosis 2
meiosis 1 (features/review)
cell goes thru PMAT 1
homologs pair up during prophase 1 (bivalents)
bivalents held together by synaptonemal complex proteins
exchange of DNA occurs b/n homologs (crossing over)
homologous pairs align in metaphase I (independent assortment)
homologs separate and are segregated in Anaphase 1
telophase I and cytokinesis occur
result is 2 haploid cells (2 chromatids per chromosome)
interkinesis: period of rest before meiosis II
meiosis I results in…
2 haploid cels (2 chromatids per chromosome)
meiosis 2 – summary
how many (haploid/diploid) cells at the beginning of meiosis 2 (# chromatids per chromosome)?
does DNA replication occur in meiosis II?
2 haploid cells at the beginning of meiosis II (2 chromatids per chromosome)
no DNA replication in meiosis II
meiosis 2 overview:
cell goes thru PMAT II
sister chromatids segregate during anaphase II
telophase II and cytokinesis occur
result is 4 haploid cells (1 chromatid per chromosome)
haploid/diploid and chromatid # game:
cell prior to S-phase
diploid
1-chromatid chromosomes
haploid/diploid and chromatid # game:
after S-phase but prior to Meiosis I
diploid
2-chromatid chromosomes
haploid/diploid and chromatid # game:
after Meiosis I prior to Meiosis II
haploid
2-chromatid chromosomes
haploid/diploid and chromatid # game:
after Meiosis II
haploid
1-chromatid chromosomes
meiosis/mitosis combine to generate life
meiosis produces haploid ovum
meiosis produces haploid sperm
fertilization produces diploid zygote
mitosis produces whole organism
