cell division your body is composed of more than a billion cells
TRANSCRIPT
Cell DivisionCell Division
Your body is composed of Your body is composed of more than a billion cellsmore than a billion cells
Why must cells divide?Why must cells divide?
They are continually They are continually dying and must dying and must produce new cellsproduce new cells
An identical copy of An identical copy of your hereditary your hereditary information is in information is in the nucleus of the nucleus of each and every each and every body cell called a body cell called a somatic cellsomatic cell dbb.urmc.rochester.edu/.../photo_gallery.
ChromosomesChromosomes
The genetic information or blueprint The genetic information or blueprint that is organized into 46 that is organized into 46 chromosomes (each contains about chromosomes (each contains about one to two thousand genes)one to two thousand genes)
KaryotypeKaryotypeHuman Human
chromosome chromosome number: 46number: 46
KaryotypeKaryotype – order – order of of chromosomes chromosomes from tallest to from tallest to smallest.smallest.
Every time a cell divides it must copy Every time a cell divides it must copy the chromosomesthe chromosomes
Goal of MitosisGoal of Mitosis
is to allow for growth is to allow for growth maintain tissuesmaintain tissues
Baby
Grow to adult
Stages of Mitosis is IPMATStages of Mitosis is IPMAT
Mitosis animation: http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__mitosis_and_cytokinesis.html
InterphaseInterphase Time between divisions – cell spends Time between divisions – cell spends
90% of its life here90% of its life here DNA is copied hereDNA is copied here Typical human cell divides every 24 Typical human cell divides every 24
hourshours
Your nucleus initially contained six un-Your nucleus initially contained six un-replicated chromosomes, and now it replicated chromosomes, and now it contains six replicated chromosomes. contains six replicated chromosomes.
The two identical copies of each The two identical copies of each chromosome are calledchromosome are called sister sister chromatidschromatids
They remain attached at a point They remain attached at a point called thecalled the centromere centromere
ProphaseProphase Chromosomes Chromosomes
condense (are condense (are visible)visible)
Sister chromatids Sister chromatids pair up.pair up.
Nuclear Nuclear membrane membrane disappearsdisappears
MetaphaseMetaphase
Paired chromatids Paired chromatids line up in the line up in the middle of cellmiddle of cell
AnaphaseAnaphase
Chromatids are pulled into Chromatids are pulled into the apart. They are dragged the apart. They are dragged through the cytoplasm (V-through the cytoplasm (V-shaped)shaped)
TelophaseTelophase Daughter Daughter
chromosomes chromosomes reach the polesreach the poles
Cells start to Cells start to separateseparate
Nuclear membrane Nuclear membrane re-formsre-forms
Cytokinesis Cytokinesis (Cell Cutting)(Cell Cutting)
The two daughter The two daughter cells separatecells separate
At the end of Mitosis, At the end of Mitosis, each daughter cell each daughter cell has an identical set has an identical set of duplicate of duplicate chromosomeschromosomes
They are called They are called SomatesSomates – – body cellsbody cells
Mitosis StagesMitosis Stages
Mitosis animation Mitosis animation http://www.sumanasihttp://www.sumanasinc.com/webcontent/nc.com/webcontent/animations/content/animations/content/mitosis.htmlmitosis.html
Interphase is subdividedInterphase is subdividedG1 – Gap 1 or growth 1 G1 – Gap 1 or growth 1 cell carries out normal functionscell carries out normal functions
G1 is a period of activity in which cells do most G1 is a period of activity in which cells do most of their growing, increasing in size and of their growing, increasing in size and synthesizing new proteins and organellessynthesizing new proteins and organelles
SS
SynthesisSynthesis
– – DNA is copied to prepare to divideDNA is copied to prepare to divide it synthesizes (to make) a duplicate it synthesizes (to make) a duplicate
set of DNAset of DNA
G2G2
G2 – Gap 2 G2 – Gap 2 is where the organelles and molecules is where the organelles and molecules
required for cell division are produced.required for cell division are produced.
M phase then CytokinesisM phase then Cytokinesis
Mitosis takes about an hour (most Mitosis takes about an hour (most time spent during G1, S and G2 time spent during G1, S and G2 phase) phase)
PMATPMAT
Check pointsCheck points G1 – Checks DNA damage before begins G1 – Checks DNA damage before begins
replication (S phase), if damaged then replication (S phase), if damaged then repaired or self destructs if cannot repair.repaired or self destructs if cannot repair.
G2 – Checks DNA to see if properly G2 – Checks DNA to see if properly copied during S phasecopied during S phase
M – checks to ensure spindle fibers M – checks to ensure spindle fibers attach properly during metaphaseattach properly during metaphase
http://www.cellsalive.com/cell_cycle.htmhttp://www.cellsalive.com/cell_cycle.htm
How does Mitosis lead to How does Mitosis lead to Caner?Caner?
Cancer is basically a disease of mitosisCancer is basically a disease of mitosis
What is happening?What is happening?The normal checkpoints that The normal checkpoints that
regulate mitosis are ignored or regulate mitosis are ignored or overridden by cancer cell.overridden by cancer cell.
How does it occur?How does it occur?
a change in function or a a change in function or a DNA DNA mutationmutation occurs in one of several occurs in one of several genesgenes (proteins) that normally (proteins) that normally function to control growthfunction to control growth
ResultResult
Once these crucial Once these crucial Cell Cycle genesCell Cycle genes start behaving abnormally, cancer start behaving abnormally, cancer cells start to proliferate wildly by cells start to proliferate wildly by repeated, uncontrolled mitosisrepeated, uncontrolled mitosis
Tumor production: Tumor production: http://www.youtube.com/watch?http://www.youtube.com/watch?v=_ZEysIhDsok&feature=relatedv=_ZEysIhDsok&feature=related
Examples:Examples:
(1)(1) p53 protein p53 protein can can senses DNA senses DNA damage and damage and halts progression halts progression of cell cycle. Also of cell cycle. Also known as tumor known as tumor suppressor gene.suppressor gene.
However, p53 is However, p53 is mutated in over mutated in over 50% of all human 50% of all human cancers. cancers.
(1)(1) BRCA 1BRCA 1 genegene, , the "Breast the "Breast Cancer Gene"Cancer Gene" normally repairs normally repairs mutations in PTEN mutations in PTEN gene which gene which suppress tumor suppress tumor formationformation
but if a gene contains but if a gene contains mutations such mutations such that BRCA1 does that BRCA1 does not work properly, not work properly, tumor formation tumor formation can begincan begin
MeiosisMeiosis Cell Division to make Cell Division to make
sex cells sex cells (sperm and eggs)(sperm and eggs)
Chromosome number Chromosome number is halved creating is halved creating these cells these cells ex. 46 ex. 46 23 23
Meiosis animation: Meiosis animation: http://www.sumanasinhttp://www.sumanasinc.com/webcontent/anic.com/webcontent/animations/content/meiomations/content/meiosis.htmlsis.html
Diploid vs. HaploidDiploid vs. HaploidDiploid – two or a pair of Diploid – two or a pair of
chromosomechromosome
Haploid – 1 set of chromosomesHaploid – 1 set of chromosomes
Examples:Examples:
Diploid = 2 Diploid = 2 4488
Haploid = 1 Haploid = 1 2244
YOU TRY: If the diploid YOU TRY: If the diploid chromosome number is 28, chromosome number is 28, what is the haploid number?what is the haploid number?
Stages : Stages : IPMAT IPMAT then then PMAT IIPMAT II
Crossing Over (independent Assortment) - tetrad
Crossing OverCrossing Over
Homologous Homologous chromosomes can chromosomes can swap information, swap information, increasing increasing variability in variability in offspringoffspring
Takes place in Takes place in prophaseprophaseTetrad – set of 4
chromosomes
Homologous ChromosomesHomologous Chromosomes The two versions of each chromosomeThe two versions of each chromosome One from mom, one from dadOne from mom, one from dad
GametesGametesGametes are sex cellsGametes are sex cells
Sperm Sperm
EggEgg
Each are haploid – half the number of Each are haploid – half the number of original set of chromosomesoriginal set of chromosomes
Diploid = 46 Diploid = 46
Haploid = 23Haploid = 23
SpermatogenesisSpermatogenesis Creates four functional sperm cellsCreates four functional sperm cells
OogenesisOogenesis Creates one functional Ovum (egg) Creates one functional Ovum (egg)
and 3 polar bodies and 3 polar bodies
Gametes – sex cellsGametes – sex cells
Products of meiosis in Products of meiosis in males formed in males formed in testes?testes?
A: 4 spermA: 4 sperm
Products of meiosis in Products of meiosis in females formed in females formed in ovaries?ovaries?
A: 1 functional egg A: 1 functional egg (the other 3 cells are (the other 3 cells are not functional and are not functional and are reabsorbed by the reabsorbed by the body?body?
Humans have 46 homologous chromosomes (23 pairs)
Stages of MeiosisStages of MeiosisInterphase:Interphase: same as Mitosis same as Mitosis
Prophase 1: Prophase 1: Same except for Same except for Crossing - over can occur – leads to independent Crossing - over can occur – leads to independent
assortment (life is a box of chocolates)assortment (life is a box of chocolates)
Metaphase 1Metaphase 1: Same except that form a tetrad : Same except that form a tetrad Homologous chromosomes that align at the equatorial Homologous chromosomes that align at the equatorial
plate. plate.
Anaphase 1Anaphase 1: Same except that the Homologous pairs : Same except that the Homologous pairs separate with sister chromatids remaining together. separate with sister chromatids remaining together.
Telophase 1Telophase 1: Same except each daughter contains only : Same except each daughter contains only one chromosome of the homologous pair (not a pair of one chromosome of the homologous pair (not a pair of chromosomse).chromosomse).
Second StageSecond StageProphase 2Prophase 2: same as mitosis : same as mitosis
Metaphase 2Metaphase 2: same as mitosis: same as mitosis
Anaphase 2Anaphase 2: Centromeres divide and sister chromatids : Centromeres divide and sister chromatids migrate separately to each pole. (same as mitosis)migrate separately to each pole. (same as mitosis)
Telophase 2Telophase 2: Four haploid daughter cells instead of two. : Four haploid daughter cells instead of two.
. Daughter cells have half the number of . Daughter cells have half the number of chromosomes found in the original parent cell chromosomes found in the original parent cell and with crossing over, are genetically different.and with crossing over, are genetically different.
Timing in MeiosisTiming in MeiosisWhen do Females produce their eggs?When do Females produce their eggs? Prior to birthPrior to birth
What do Males produce sperm?What do Males produce sperm? Once hit pubertyOnce hit puberty
Helpful saying Helpful saying I don’t use “Mi-Toes-es” for making sperm I don’t use “Mi-Toes-es” for making sperm or eggs!or eggs!
Differences between Mitosis Differences between Mitosis and Meiosisand Meiosis
MitosisMitosis MeiosisMeiosis
IPMATIPMAT IPMAT I & PMAT IIIPMAT I & PMAT II
DiploidDiploid HaploidHaploid
SomateSomate GameteGamete
2 cells2 cells 4 cells4 cells
Non-Disjunction- when chromosomes do not Non-Disjunction- when chromosomes do not separate correctly during meiosis.separate correctly during meiosis.
End up with 47 or 45 in each new cell. End up with 47 or 45 in each new cell.
Example:
Downs Syndrome = Trisomy 21 (3 chromosomes 21)
Turner’s Syndrome = one X and no second sex chromosome