mitosis and meiosis. differences in human cell types somatic cells somatic cells-“regular”...
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Mitosis and MeiosisMitosis and Meiosis
Differences in Human Cell Differences in Human Cell TypesTypes
Somatic CellsSomatic Cells
-“regular”-“regular”
-diploid (46 -diploid (46 chromosomes)chromosomes)
-Identical DNA -Identical DNA throughout bodythroughout body
Gamete-Gamete-
-sex cells-sex cells
-haploid-haploid
-sperm and eggs-sperm and eggs
MitosisMitosis
Division of somatic Division of somatic cellscells
Necessary for Necessary for tissue growth or tissue growth or repairrepair
5 steps5 steps– DNA must be DNA must be
duplicatedduplicated– 4 step process to 4 step process to
divide DNAdivide DNA
InterphaseInterphase
Longest stage of Longest stage of cell’s life cyclecell’s life cycle
Part of the cell Part of the cell cycle in which DNA cycle in which DNA replication occursreplication occurs
Towards the end, Towards the end, the cell prepares the cell prepares for divisionfor division
ProphaseProphase
Cell with 2 sets of Cell with 2 sets of DNADNA
Chromatin (loose Chromatin (loose DNA) condenses DNA) condenses into chromosomesinto chromosomes
First step in which First step in which chromosomes are chromosomes are visible.visible.
MetaphaseMetaphase
Chromosomes line Chromosomes line up on “equator” of up on “equator” of cellcell
Spindle Fibers Spindle Fibers attach to attach to centromere (center centromere (center of chromosome) of chromosome) from centrioles at from centrioles at each poleeach pole
AnaphaseAnaphase
Chromosomes are Chromosomes are split into two (each split into two (each still identical) and still identical) and pulled towards pulled towards opposite poles.opposite poles.
TelophaseTelophase
Daughter cells Daughter cells separate by separate by pinching apartpinching apart
Nuclear division Nuclear division completecomplete
Finishes with Finishes with cytokinesis cytokinesis (division of (division of cytoplasm)cytoplasm)
After MitosisAfter Mitosis
Two identical Two identical daughter cellsdaughter cells
Have identical Have identical (diploid) genome(diploid) genome
CancerCancer
Uncontrolled growth of cellsUncontrolled growth of cells
Proteins called oncogens and Proteins called oncogens and protooncogens usually control cell cycleprotooncogens usually control cell cycle
If they get damaged, cell cycle is If they get damaged, cell cycle is uncontrolleduncontrolled
MeiosisMeiosis
Cell division in Cell division in gametesgametes
Same stages as Same stages as mitosismitosis
In meiosis, DNA In meiosis, DNA undergoes another undergoes another divisiondivision
Meiosis contd.Meiosis contd.
Leads to 4 haploid Leads to 4 haploid daughter cells (23 daughter cells (23 chromosomes each) chromosomes each) Why?Why?
In females, 1 of the In females, 1 of the daughter cells is daughter cells is retained as ovumretained as ovum
In males, all 4 become In males, all 4 become nucleus of spermnucleus of sperm
When Meiosis goes wrong..When Meiosis goes wrong..
Non-disjunction-Non-disjunction-both chromosomes both chromosomes pulled into one pulled into one daughter cell, daughter cell, resulting in 47 resulting in 47 chromosomes after chromosomes after fertilizationfertilization
ResultsResults
Downs syndrome – Downs syndrome – trisomy 21trisomy 21
Edwards syndrome Edwards syndrome – trisomy 18– trisomy 18
Patau’s syndrome – Patau’s syndrome – trisomy 13trisomy 13