BIOL10004 Lecture Notes - Lecture 5: Plant Cell, Prometaphase, Metaphase

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28 Jun 2018
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LECTURE 5 - CELL DIVISION AND MITOSIS
CELL DIVISION IN PROKARYOTES
Binary Fission – rapid cell division
oFtsZ protein (filament temperature sensitive) – mutant protein
Homologue (ancestor/relative) of the eukaryotic cytoskeletal protein tubulin
Essential for cytokinesis b/c the FtsZ ring pinches the cell apart
Also involved in division of chloroplast + mitochondria
Starts with singular tube of double-stranded DNA
oReplicates
oAttaches itself to plasma membrane
oCells pinch apart to create 2 daughter cells
FtsZ form cytokinetic ring where cells are about to divide
oConstrict middle of cell
oRecruits other proteins, allow membrane to pinch off
Mutations in FtsZ – Alter bacterial cell shape & division frequency
oi.e. can cause cell to be abnormally long or twisted divisions
CELL CYCLE IN EUKARYOTES – 3 CHECKPOINTS
Interphase: occurs prior to mitosis. All organelles increase in number and DNA is replicated
during this process
oGap 1 phase: cell grows; organelles, enzymes and other molecules increase in number
First point of check before synthesis
G0 = cells that will never divide ever again
oSynthesis phase: DNA replicates by DNA polymerase. Chromosomes are not visible
oGap 2 phase: growth phase when chromosomes have been replicated
If there is an issue, cell must be terminated
Second checkpoint
Mitosis – the process of chromosome condensation, nuclear envelope breakdown, sister
chromatid separation dn formation of two daughter nuclei in eukaryotes
oAlready has replicated DNA
oProphase
Chromosomes fully condensed
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Document Summary

Binary fission rapid cell division: ftsz protein (filament temperature sensitive) mutant protein. Homologue (ancestor/relative) of the eukaryotic cytoskeletal protein tubulin. Essential for cytokinesis b/c the ftsz ring pinches the cell apart. Also involved in division of chloroplast + mitochondria. Starts with singular tube of double-stranded dna: replicates, attaches itself to plasma membrane, cells pinch apart to create 2 daughter cells. Ftsz form cytokinetic ring where cells are about to divide: constrict middle of cell, recruits other proteins, allow membrane to pinch off. Mutations in ftsz alter bacterial cell shape & division frequency: i. e. can cause cell to be abnormally long or twisted divisions. All organelles increase in number and dna is replicated during this process: gap 1 phase: cell grows; organelles, enzymes and other molecules increase in number. G0 = cells that will never divide ever again: synthesis phase: dna replicates by dna polymerase. Chromosomes are not visible: gap 2 phase: growth phase when chromosomes have been replicated.

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