Chapter 6: Cell Reproduction Two Types of ReproductionTwo Types of Reproduction a. Sexual – create genetic diversity (offspring not identical to parents) b. Asexual – offspring is identical to parent.

Binary Fission Asexual reproductionAsexual reproduction Takes place in prokaryotic cellsTakes place in prokaryotic cells 2 stages:2 stages: –DNA is copied –Cell pinches apart into two identical cells

6-1 chromosomes Eukaryotic cells form 1. DNA copied 2. Chromatids form (exact copies of DNA) Centromere – hooks chromatids together

Chromosome number Homologous chromosomes – similar is size, shape, genetic content.Homologous chromosomes – similar is size, shape, genetic content. –Diploid cell – two sets of chromosomes ( one from each parent) –Haploid cell – one set of chromosomes (sex cells)

Human Chromosome # Humans – 46 chromosomesHumans – 46 chromosomes –23 from Mom –23 from Dad Sex Chromosomes – determine sexSex Chromosomes – determine sex XX – female, XY - male

Somatic cells vs Gamates Somatic cellsSomatic cells body cells (liver, skin) Diploid (46)Diploid (46) Gamate cells – sperm or egg cells Haploid (23) Zygote – two gamates fuse

Edwards syndrome Edwards syndrome

Down’s Syndrome

Chromosome Abnormalities

1. Inversion Inversion – a piece of chromosome breaks off and rejoins in the reverseInversion – a piece of chromosome breaks off and rejoins in the reverse ABCDEF (normal chromosome)ABCDEF (normal chromosome) ACBDEF (inversion)ACBDEF (inversion)

2. Translocation Translocation – a piece of chromosome breaks off and attaches to another chromosomeTranslocation – a piece of chromosome breaks off and attaches to another chromosome

Translocation

3. Deletion – Part of a chromosome breaks off and is lost. NormalNormal – DeletionDeletion –12567 Cri du chat is a rare syndrome (1 in 50,000 live births) caused by a deletion on the short arm of chromosome 5

Cri du Chat Karyotype

4. Nondisjuction - One or more chromosomes fail to separateOne or more chromosomes fail to separate –Trisomy – gamate has one extra chromosome –Monosomy – gamate is missing a chromosome

Nondisjuction Trisomy ics.utah.edu/con tent/begin/traits/ predictdisorder/i ndex.htmlhttp://learn.genet ics.utah.edu/con tent/begin/traits/ predictdisorder/i ndex.html

Nondisjuction Monosomy Turners Syndrome – female with a missing X chromosome

Cell Cycle – cells lifespan ts/ /index.html115075

Cell Cycle Steps G 1 Phase – rapid growthG 1 Phase – rapid growth S phase – DNA copied (chromatids)S phase – DNA copied (chromatids) G 2 phase – prepare to divideG 2 phase – prepare to divide Mitosis- nucleus dividesMitosis- nucleus divides Cytokinesis- cytoplasm dividesCytokinesis- cytoplasm divides IPMAT cIPMAT c

Importance??? Growth Replacement Cancer Regeneration of…

Cancer? Unregulated mitosis How does it begin?

Mitosis – division of nucleusdivision of nucleus 4 Stages of :4 Stages of : 1.Prophase 2.Metaphase 3.Anaphase 4.Telophase

Prophase Chromosomes thickenChromosomes thicken Nuclear membreane breaks downNuclear membreane breaks down Nuclelous issapearsNuclelous issapears Spindle fibers formedSpindle fibers formed Centrioles appearCentrioles appear

metaphase Each chromosome lines up midway between polesEach chromosome lines up midway between poles

Anaphase Centromeres divideCentromeres divide 2 chromatids separate2 chromatids separate chromosomes pulled to the opposite ends of the cellchromosomes pulled to the opposite ends of the cell

Telephase Chromosomes arrive at opposite polesChromosomes arrive at opposite poles Spindle fibers disappearSpindle fibers disappear Nuclear membrane reappearsNuclear membrane reappears Chromosomes uncoil (lighten)Chromosomes uncoil (lighten)

Cytokinesis Division of the cytoplasm Result – 2 Identical cells

Name stage of mitosis