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Growth and Division of the Cell (Cell Division of Prokaryotes (DNA (one or…
Growth and Division of the Cell
Growth Phase of the Cell Cycle
3 distinct phases
G1 Phase
first stage after cell division
cell begins normal metabolism
synthesis of nucleotides for DNA replication
prepares cell for mitosis
cell matures and differentiate
S phase
genes in nucleus are replicated
sequence of nucleotides vary
variety gives way for genome of the organism
types of genes stored as info for
enzymes
hormones
structural proteins
genes begin to become linear
genes attached to one another by linking DNA
chromosomes
Centromere located in center and telomeres at the ends
two identical chromatids after S Phase
becomes twice as large
Eukaryotes
histones used for protection and structure of DNA
DNA replication may occur in more then 1 cycle
nucleus becomes enlarged
endoreduplication
hairs cells
cells requiring rapid, and intense metabolism
glandular cells
cells also rich in ribosomes
large amounts of protein
G2 Phase
after S Phase
lasts only 3-5 hours
tubulins synthesized for spindle microtubules
proteins produced
processing chromosomes
break down nuclear envelope
factors for nuclear division
cell active during interphase
Division Phase of the Cell Cycle
Mitosis
duplication division
genes copied 1st
set of genes separated 2nd
each packed into their own nucleus 3rd
4 phases
Prophase
chromosomes condense
histones association changed
begin to coil, making them thicker
nucleolus becomes less distinct or disappears
breaks into vesicles
daughter chromosomes made in previous interphase migrate to poles
produce spindle
microtubules
run from pole to a centromere
point of attachment is kinetochore
each centromere has two kinetochore faces
one for each pole
Metaphase
spindles pull chromosomes to center
metaphase plate
separaze produced at the end
protein degrading enzyme
eats away cohesin
two chromatids of each chromosome separated
number of chromosomes doubled but size is halved
Anaphase
spindles shorten
pull daughter chromosome from its twin towards opposite poles
chromosomes pulled into a compact space
Telophase
nuclear envelope fragments attracted to chromosomes
connect and form nuclear envelopes at ends of the cell
chromosomes begin to uncoil
new nucleoli appear
ribosomal genes become active
ribosome subunits produced
spindle dispensary completely
reversal of prophase
Cytokinesis
division of protoplast
daughter cells receive organelles
random distribution
seperation of cells
preprophase band
during prophase
no prophase = no band
microtubules and actin filaments form band around cell
interior of plasma membrane
identifies plane of division
where cell wall will attach to new cell
determines how large cells produced will be
Phragmoplast
in plants
microtubules aligned parallel to spindle
actin also present
trap dictyosome vesicles
fuse into flat, plate like vesicles
two primary walls form and middle lamella
forms in center
grows outward toward original wall
cell plate
phragmoplast, vesicle, and walls
meets mother cells plasma membrane
two fuse
vesicle membrane becomes part of plasma membrane of daughter cells
cell walls also go through this
Meiosis
daughter nuclei are replicates of original
2 gametes fuse (haploid cells)
create zygote (diploid cell)
becomes an adult
each contain one set of chromosomes
Reduction Division
two rounds of division
Meiosis I & II
prevents S Phase from occurring after first
occurs in only production of reproductive cells
gametes
spores
stamens and ovaries
Meiosis I
Prophase I
all events of prophase in mitosis
Special interactions of chromosomes
divides Prophase I into 5 stages
Leptotene
chromosomes condense
Zygotene
pairing of chromosomes
homologous chromosomes
Pachytene
shorter and thicker chromosomes
crossing over occurs
Diplotene
homologous chromosomes move away from each other, but dont separate
held together by chiasmata
1 more item...
Diakinesis
homologs seperate
chiasmata pushed to ends of chromosome
become untangled and pair at centromeres
Metaphase I
Spindles move tetrads to center of cell
Metaphase plate formed
Anaphase I
homologous chromosomes separate
cohesin not digested
consist of two chromatids
move to opposite ends
two nuclei formed
both haploid
two sets of genes
Telophase I
Chromosomes uncoil
nucleolus and nuclear envelope reappear
sometimes may be skipped
Meiosis II
if telophase I occurs the prophase II necessary
nuclei undergo
two chromatids separated
each have haploid set
double cytokinesis
four haploid cells produced
Less Common Types of Division in Plants
coenocyte
large cell
many nuclei
multinucleate
karyokinesis occurs, but no cytokinesis
without nuclear division
common in
algae
fungi
tissues of seeds
cells multinucleate
cell wall surrounds each nucleus with cytoplasm
Cell Division in Algae
Nuclei
unusual characteristics
common in
dinoflagellates
no histones in nucleus
brown algae
euglenoids
some green algae
gaps in nuclear envelope
microtubules pass through
Cytokinesis
several types occur
with or without cell wall
cell division without
plasma membrane pinches in two
forms cleavage furrow
Cell division with
similar to plants
phragmoplast formed
dictyosome vesicles establish cell plate
grows outward
fuses with parent cell wall
Green algae
occurs by different method
spindle depolymerizes quickly
daughter cells close together
microtubules form in the middle
phycoplast
furrowing
cell plate formation
nuclear envelope does not break down during mitosis
Cell Division of Prokaryotes
mitosis and meiosis do not occur
cytokinesis much simpler
occurs via infurrowing
plasma membrane pulled inward
cross wall grows inward
splits becoming two walls
two daughter cells released
pinches in two
DNA
one or several rings
attached to plasma membrane
pulled apart as cell and membrane grow
no protective histones
Division of Chloroplasts and Mitochondria
contain circles of naked DNA
separated by membrane growth
division of organelles
infurrowing
pulled in two
daughter cell must receive at least one
play a role in
function
growth
contain DNA necessary to produce organelle
