Cell Reproduction
Mitosis and that
- Created by: Uxia Lorenzo
- Created on: 16-12-12 14:26
Mitosis
Method of cell division
nucleus divides into daughter nuclei each containing the same number of chromosones
Normally cells divide to replace dead or missing cells
cells lining the gut divide about twice a day
nerve cells dont divide
In an embryo, cell division occurs every 30 mins
Meiosis
reproductive cells undergo Meiosis
four dissimilar cells are formed
each cell contains only half of the parental chromosonal number
Chromosone
Strand of DNA and proteins in the nucleus of eukaryotic cells that carries the genes
made of Chromatin DNA complexed with protein
Organised into nucleosomes
Chromatin has the ability to condense into tightly packed structure - heterochromatin
Only visible by light microscope
Heterochromatin and Euchromatin
Heterochromatin - chromatin organisation, lines the nuclear membrane at the pores
Euchromatin - threadlike, delicate, abundant in active transcribed cells, regions of DNA to be transcribed or duplicated, must be coiled before genetic code can be read.
All the human body's nucleated cells contain 46 chromosomes (23 pairs)
Contain all the information that governs all cellular activitys
DNA molecules - form of genes
DNA molecule regulate specific functions
blueprint determines synthesis of an RNA molecule or polypeptide
Not visible in non dividing cells
Cell cycle
Stages are G1, S (synthesis DNA replication) , G2, M (mitosis)
two cell division events need to be controlled
entry into S phase - replication
entry into M phase - Mitosis
when to initiate replication
when to initiate chromosonal condensation
M Phase entry
the accumulation of a specific cellular mass
Some cells need to reach a specific growth rate for mitosis to begin
Time between Mphases controlled by timer genes
M phase requires completion of S phase
insure full DNA complements - completion of chromosonal replication factor
Reproduction Stages - INTERPHASE (before mitosis) , PROPHASE, MATAPHASE, ANAPHASE, TELOPHASE ----- CYTOKINESIS
Interphase
Not part of Mitosis
Longest Phase
Where the cell grows
DNA duplicated, prepared for division
G1 phase - normal metabolic cellular
S phase - DNA duplicates
G2 phase - structures for mitosis are formed
Prophase
Chromatin condenses into chromosomes
Sister chromatids joined by centromere
Nuclear envelope starts to break up
Nucleolus disapeers
Metaphase
chromosomes line up at equator by spindle fibres from opposite ends of the cell
Kinectochore= proteinaceous region that forms at both sides of centromere, binds to microtubules to pulls sister chromatids apart
Anaphase and Telophase
Anaphase - Two sister chromatids break apart and are now seperate chromosomes that move to opposite spindle pores
Telophase
Chromosomes decondense
New patches of membrane fuse to form new nuclear envelope around them
Cytokinesis
Daughter cells are pulled apart
Contraction of microfilaments
Control of Mitosis
Cell divides too often - cancer
Not often enough - death
Controls - growth factors, growth suppressors P53
Meiosis
unique type of cell division
only produces gametes
number of chromosomes halved
requires two divisions with no S phase
gene recombination so its genetically unique
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