Unicellular organisms cell division reproduction Multicellular organisms cell div needed for development amp for reproduction meiosis Mitosis gives each cell complete set of genetic material ID: 1042490
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1. Chapter 12 -- Cell Division & MitosisUnicellular organisms cell division = reproductionMulticellular organisms cell div. needed for development & for reproduction (meiosis)Mitosis gives each cell complete set of genetic material and cytoplasmic organellesOne cell divides to form twogenetically identical daughter cellsMitosis vs. MeiosisNucleolus & Nucleuschromosomes
2. Before mitosis (interphase)each chromosome is duplicatedA duplicated chromosomehas two sister chromatidsEach sister chromatid containsexactly the same genes.In mitosis each daughter cellgets one sister chromatidfrom each chromosomeCell Cycle: ordered setof events from one cell division to the nextinterphase - mitosis - interphase - etc.centromereFig 12.4
3. Prophase: condensation of chromosomes formation of spindle breakdown of nuclear envelope & nucleus attachment of chromosomes to spindleCentrosomeand centriolesorganizethe spindle(composedof micro-tubules)Fig 12.7
4. Metaphase: chromosomes align at center of cellCytokinesis: cell divides in twoTelophase: reverses prophaseAnaphase: centromeres split - one sister chromatid from each chromosome moves to one centromereFig 12.7
5. Meiosis -Specialized cell division for sexualreproductionMeiosis reducesthe chromosomenumber by 2Diploid (2n) cellshave two copies ofeach chromosomeHaploid cells (n) haveone copy of eachchromosome.Meiosis converts 2ncells into n cells(gametes)Fig 13.5
6. Human Karyotype: 46 chromosomes, 23 pairsDiploid organisms have two copies of each chromosome22 pairs of autosomes, one pair sex chromsomes (X & Y)SimilarTo Fig 13.3
7. Most Organisms are Diploid (2N)Homologous Chromosomes - - carry the samegenes but may have different allelesAABCCBaabCCb
8. MEIOSISOne diploid cell divides twice and forms 4 haploid cellsEach daughter cell gets one chromatid from each pair of homologous chromosomes
9. First Division (Meiosis I)homologous chromosomes are separated into different daughter cellschromosome recombination (crossing over) occursSecond Division (meiosis II)no DNA replication before divisionsister chromatids are separated into different daughter cellsMeiosisFig 13.7
10. Meiosis IHomologous chromosomes pair and crossover during Propohase ICrossingover - reciprocal exchange of chromatid armsFig 13.8
11. Meiosis IICells immediately divide again (no DNA replication)Division is like mitosis (sister chromatids are separated) Fig 13.8
12. Pure-breeding peasdiffering in 7 pairs of traitsSeed Shape - round vs. smoothSeed Color - yellow vs. greenPod Shape -Flower coloretc.
13. Pure-Bred White FlowersPure-Bred White FlowersX100 % White FlowersPure-Bred RedFlowersPure-Bred Red FlowersXX100 % RedFlowers
14. Pure breeding red X Pure breeding whitePF1F2
15. Mendel’s Law of Segregation1. Each trait is controlled by a pair of factors GENES2. When 2 different factors for a trait are present in an individual on is DOMINANT and one is RECESSIVE ALLELES -- alternate forms of a gene3. During gamete formation the paired factors SEGREGATE RANDOMLY
16. Partial dominance and CodominanceNeither allele is dominant or recessiveHeterozygous individuals havea distinct phenotypePartial dominance - heterozygote has an intermediate phenotypeCodominance - heterozygote expresses both alleles
17. DIHYBRID CROSS
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19. Punnett Square for a Dihybrid Cross
20. Outcome of the Dihybrid Cross
21. Inheritance of Flower Color in SnapdragonsRed X WhitePinkPink X Pink1 Red : 2 Pink : 1 WhiteF2F1P1F1Partial DominanceAka Incomplete Dominance
22. Discovery of linkageThe White eye mutation in Drosophilais linked to inheritance of sexThomas Hunt Morgan -- 1910Females are XXMales are XYWhite eyes are found moreoften in malesWhite eye is due to a recessive gene on the XThe Y chromosome carries no corresponding allele
23. White-eyed maleXwild type femaleF1 - all wild typeF2all females wildtypemales are 50-50wild type or white eyedF1 X F1
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25. malefemale