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BIOL 320
chp2set.ppt
CHROMATIN:
EUCHROMATIN & HETEROCHROMATIN
RESTING (NONDIVIDING) CELL
QUIESCENCE
INTERPHASE
CHROMOSOME
APPEARANCE
NUCLEUS PREPARING TO DIVIDE
CHROMOSOME DUPLICATION
DNA REPLICATION
S PHASE OF CELL CYCLE
NUCLEUS DURING DIVISION
unduplicated
chromosome
duplicated
chromosome
TELOMERE
p ARM
CENTROMERE
q ARM
TELOMERE
Homologues
unduplicated
chromosome
duplicated
chromosome
Sister
sister chromatids
Homologous
pair of
duplicated
chromosomes
Sister
non-sister
chromatids
chromatids
Meiosis
2n
2n
2n
n
2n
2n
2n
2n
n
2n
2n
2n
Mitosis
2n
unduplicated
chromosome
duplicated chromosome
DNA
Replication
in
anticipation
of cell
division
unduplicated chromosome
S Phase
duplicated chromosome
Mitosis
daughter cells
(somatic)
parental cell
(somatic)
S Phase
parental cell
(gonadal):
“gonium”
Meiosis I
Meiosis II
daughter cells
(gonadal): “gametes”
Chromatin condensation
Initial pairing of
homologues
Chromosomes shorten &
thicken
Chromosomes shorten &
thicken
initial alignment, 300 nm
Chromomeres appear
Lateral elements appear
Synaptonemal complex
developed b/w bivalents
Homology search begins
Synaptonemal complex
begins
“bivalents,” duplicated
but not apparent
#bivalents = n
“synapsis,” 100 nm
Bivalents resolve to
“tetrads”
Crossing over begins
Crossing over apparent
Sister chromatids
separate
Nonsister chromatids
exchange
“chiasmata”
“Terminalization” begins
Nonsister chromatids
loosely attached
Terminalization
complete
Nucleolus & nuclear
envelope break down
Centromeres are
equatorial
Emerging Molecular Biology of Chromosome
Junctioning and Nondisjunction
unduplicated chromosome
S Phase
duplicated chromosome
Mitosis
daughter cells
(somatic)
parental cell
(somatic)
S Phase
parental cell
(gonadal):
“gonium”
Meiosis I
Meiosis II
daughter cells
(gonadal): “gametes”
CELL CYCLE and MEIOSIS
CELL CYCLE and MEIOSIS
LEPTONEMA LEPTOTENE
ZYGONEMA ZYGOTENE
PACHYNEMA PACHYTENE
DIPLONEMA DIPLOTENE
DIAKINESIS
DIAKINESIS