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molecular bio: cell, meiosis


copy deck
Gi, S, G2

precedes mitosis
G1 (gap) phase
12 hrs. avg

cell growth: synthesis of carbs, proteins, lipids
LONG G1 state (almost stops cycling!)

ex: muscle, nerve cells
mitochondria + centrioles divide during ____ phase
S phase

(both contain DNA)
cells perform their differentiated functions during ____ phase
during G1, cells are _n
2n (diploid)
during G2, cells are _n
4n (tetraploid)
6-8 hrs avg.

ALLDNA synthesis + chr replication happens here

also RNA synthesis rate increases, cell prepares for mitosis
3-4 hrs avg.

resembles G1 except cell now TETRAPLOID (4n)
in mitosis, cell goes from _n to _n
4n to 2n
6 phases of mitosis
early anaphase
late anaphase
chr condense (recognizable)

centrioles (barrel-like) visible in cytoplasm
2 copies of each chromosome separated into single chromosome called CHROMATIDS

mitotic spindle forms

centrioles begin to separatre, microtubules assemble b/w them

near end, nuclear envelope starts to rupture
nuclear envelope + nucleolus disappear

spindle moves to where nucleus was

chr move to mid-spindle + attach to MT
early anaphase
CHROMATIDS split longitudinally + migrate to cell poles

*note: after chromatids split, they are called chromosomes again
late anaphase
chr aggregate at poles

CLEAVAGE FURROW begins to form (beginning of cytokinesis)
until ANAPHASE, each chromosome contains 2 sister chromatids

after ANAPHASE each chromatid = separate chromosome
during G2, each chromosome consists of _________
2 sister chromatids, connected at centromere
telophase (cytokinesis)
nucleolus forms

nuclear envelopes form around each set of daughter chromosomes

condensed chromatin expands again + begins to reappear

cytoplasm divides by deepening cleavage furrow until --> 2 daughter cells
cells entering meiosis are called ________
primary gametes (spermatocytes or oocytes)

have same DNA content as cell entering mitosis
cells entering meiosis II are called ________
secondary gametocytes

contain 23 chromosomes (each consisting of 2 sister chromatids)
meiosis occurs in______
germ cells (sperm, ova)

2 parts, cell division in each resembles mitosis, but no DNA replication during either
meiosis reduced chromosome # by ______
genetic recombination occurs in

exchange of chr segments

occurs b/w chr within tetrad

changes allelic linkages, does NOT change gene sequence
stages of Meiosis I
prophase I
metaphase I
anaphase I
telophase I
stages of meiosis II
prophase II
metaphase II
anaphase II
telophase II
during meiosis II, _______ separate
sister chromatids (of the 23 chromosomes)
recombinbation occurs b/w
chromatids within a tetrad
meiotic prophase occurs in _ steps
3 (A,B,C)
meiotic prophase A
chromosomes condense (visible), homologous chromosomes pair (except X,Y chr; centromeres of homologues don't pair)
meiosis prophase step B
homologous chromosome pairing complete

4 chromatids appear (= tetrad)
meiosis prophase step C
chromatid segments exchanged b/w 2 paired homologous chromosomes
pt of exchange during recombination, shaped like an X
cells resulting from meiosis II


ova (plus polar body)
meiotic metaphase I
paired chromosomes line up on mitotic spindle

2 chromosomes of each homologous pair attach to MT going to opposite poles of cell
meiotic anaphase I
both chromatids migrate to same end of cell
meiotic telophase I
each daughter gets 1 part of each chromosome pair

each gets total 23 chromosomes
2nd meiotic division
similar to meiotic division except NO PRIOR DNA SYNTHESIS

23 chromosomes divide at centromere

each new daughter cell gets 23 chromatids (HAPLOID)

Deck Info