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Growth & Division of the Cell (Cell Phase of the Cell Cycle (G2 Phase,…
Growth & Division of the Cell
Cell Phase of the Cell Cycle
S Phase
genes are replicated
Linking pieces of DNA
Histone molecules complex with new DNA
G2 Phase
Cells prepare for division
Phase last 3-5 hours
Alfa and Beta tubulins are synthesized
This is for spindle microtublules
produce proteins nessesary
processing chromosomes and breaking nuclear evelop
After this stage division can occur
G1 Phase
1st stage after division
Long Part of the Cell cylce
Normal Metabolism
Division Phase of the Cell Cycle
Actual division involves two processes:
Cytokinesis- division of the cytoplasm
division of protoplast
random distribution of organelles from mother cell are passed down
in plants:
involves formation of phragmoplast
Short microtubules aligned parallel to the spindle microtubules
Meiosis 1
prophase 1
Nucleolus and nuclear membrane break down
spindles form
Microtubules attach to centromeres
Chromosomes condense and become visible
Special interactions of chromosomes occur now:
Leptotene- chromosome become distinguishable
zygotene-pairing of chromosomes occur
Pachytene- chromosome continue to condense, become shorter and thicker
Crossing over occurs
Diplotene- chromosome pairs begin to move away from each other but do not seperate
Diakinesis- chromosome pairs continue to separate and chiasmata are pushed to ends of chromosomes
metaphase 1
Spindle microtubles move tetrads to center of cell
Anaphase 1
Chromosome pairs split completely moving to opposite ends of the spindle
Telophase 1
Chromosomes are still doubled
Are in a G2 state
Meiosis 2
Prophase 2
not subdivide like pp1
metaphase 2
short and sweet version of met 1
Anaphase 2
separates new chromosome from its replicate
Telophase2
New nuclei are formed
Karyokinesis- division of nucleus
Mitosis- duplication division
Prophase
Spindle fibers attach from poles to centromere
Nucleolus becomes less distinct
Eventually disappears
Protein framework developos
Chromosomes condense
Telophase
reversal process of prophase
Nuclear envelop forms around chromosomes
Metaphase
Number of chromosomes double but size is halved
Push chromosomes to middle of cell
arrangement there is called metaphase plate
Anaphase
pull each daughter chromosome away from its twin
freeing of two kinetochore faces from each other
Less Common Types of Division in Plants
Cell division may occur without nuclear division
Most common in algae, fungi, and nutritive tissues of seeds
In lily flowers:
haploid cell involved produces an egg cell which undergos two rounds of mitosis without cytokinesis
Cell Division in Algae
gaps form in nuclear envelope
bundles of microtubules pass completely through the nucleus
cytokinesis
Algae have no wall
plasma membrane pinches in two (cleavage furrow)
Algae with wall
Similar to cytokinesis of plants
Cell Division of Prokaryotes
Does not use Mitosis or Meiosis
Use Cytokinesis
Infurrowing: plasma membrane pulls inward and finally pinches in two.
Division of Chloroplast and Mitochondria
use infurrowing or being pulled in two