cell cycle lecture 1 Flashcards
cell replication occur via elaborate series of events - stages
S and M
stage S of cell replication
DNA synthesis - replication
stage M
divide and distribute into 2 daughter cells
difference between Xenopus and Drosophilia embryo
Drosphoilis embryo does not have cytokinesis so membrane does not separate nuclei
chromatin - contain
complex of histones, non-histone proteins and nuclear DNA
chromatin function
DNA compaction and involved in regulation of DNA activities
nucleosome contain
DNA and protein (4 histones)
nucleosome
basic structural units of chromatin
histone contain
tails - no specific structure
has 2 functional domain
2 functional domains in histones
amino-terminal
histone fold
histone folds
interacting with each other to form dimers
has a hand-shake like interaction
histone octamer
formed from dimers H3-H4 and H2A-H2B - 2 copies of each
linker histones function
bind to DNA and nucleosome core
changes path of DNA that exits nucleosome
DNA exiting nucleosome
affects linker DNA accessibility
organisation of higher order chromatin fibre and chromatin compaction
30nm fibre
found in in vitro but not in in vivo
interphase nucleus
11nm fibre
beads on a string
unpacked/decondensed
unknown form of 30nm fibre
zig-zag model
determined by x-ray crystallography
non-histone protein function
binds to areas of chromatin
play regulatory role
non-histone protein structural function
50% protein mass of nuclei
higher order organisation of chromatin
chromatin arranged in loops and from higher loops
protein used in the higher order organised chromatin
CTCF and Cohesin
CTCF
protein that binds to DNA
Cohesin
4 proteins that circles the DNA keeps loop strands
regulate size of loop
TADs
topologically associating domain
groups of loops
compartments
grouped TADS
can be transcriptionally active or inactive
compartments belong to
individual chromosomal territories - occupied by single chromosomes decondensed after mitosis
staining individual chromosomes
using fluorescent staining
multi-colour FISH
visualising chromosomes shown
occupied certain areas of nucleus during interphase
not random
placement of chromosome territories
some towards periphery - nuclear membrane and other towards centre of nucleus
patterns of chromosome arrangement
specific to both cell and tissue type
structure of mitotic chromosomes during mitosis
differs from organisation of interphase chromosome
structure of mitotic chromosomes during metaphase
individual chromatid containing 1DNA molecule
joined by centromere
region where DNA ends
telomeres
organisation of folding of DNA
DNA sequence - 2nm beads of string - 11nm chromatin fibre - 30nm folded into loops - 700nm entire mitotic chromosome - 1400nm
condensin
multiprotein complex
condensin function
compresses fibres
condensing list using condensin complex
linear fibres
linear looping
axial compression
lateral compression
formation of chromatin looping in mitotic chromosomes
randomly formed
looping structure
scaffolding through the centre of chromatid
loops in interphase and mitosis
loops have different formations in interphase
cohesin
organises interphase genome
codensin
organises genomes during mitosis
G1 phase
cell cycle gap phase between M and S phase
G2
cell cycle gap phase between S to M phase
interphase
period between end of M phase and beginning of the next
mitosis
nuclear division in early M phase - duplicated chromosomes are segregated by mitotic spindle and package into nuclei
cytokinesis
cell division
in late M phase - duplicated nuclei cytoplasmic components are distributed into daughter cells
M phase
duplicate chromosomes segregated and packages into daughter nuclei and distributed into daughter cells
S phase
DNA replication and chromosomes duplication occurs
