Cell Cycle  Stages in growth & division  G1 Phase  S Phase  G2 Phase  M Phase  Cytokinesis copyright cmassengale

G1 Phase  First growth stage  Cell increases in size  Cell prepares to copy its DNA copyright cmassengale

Synthesis Phase  Copying of all of DNA’s instructions  Chromosomes duplicated copyright cmassengale

G2 Phase  Time between DNA synthesis & mitosis  Cell continues growing  Needed proteins produced copyright cmassengale

M Phase  Cell growth & protein production stop  Cell’s energy used to make 2 daughter cells  Called mitosis or karyokinesis (nuclear division) copyright cmassengale

Life Cycle of a Cell Mitosis is a cycle with no beginning or end. copyright cmassengale

Interphase – Resting Stage  Cells carrying on normal activities  Chromosomes aren’t visible  Cell metabolism is occurring  Occurs before mitosis copyright cmassengale

Interphase

Stages of Mitosis  Prophase  Metaphase  Anaphase  Telophase copyright cmassengale

Cells Undergoing Mitosis copyright cmassengale

Steps in Prophase  DNA coils tightly & becomes visible as chromosomes  Nuclear membrane disappears  Nuceolus disappears  Centrioles migrate to poles  Spindle begins to form copyright cmassengale

Prophase

Eukaryotic Chromosome copyright cmassengale

Human Chromosomes copyright cmassengale

Steps in Metaphase  Spindle fibers from centrioles attach to each chromosome  Cell preparing to separate its chromosomes  Cell aligns its chromosomes in the middle of the cell copyright cmassengale

Metaphase

Steps in Anaphase  Cell chromosomes are separated  Spindle fibers shorten so chromosomes pulled to ends of cell copyright cmassengale

Mitotic Spindle copyright cmassengale

Anaphase

Steps in Telophase  Separation of chromosomes completed  Cell Plate forms (plants)  Cleavage furrow forms(animals)  Nucleus & nucleolus reform  Chromosomes uncoil copyright cmassengale

Telophase Plant Animal copyright cmassengale

Cytokinesis  Occurs after chromosomes separate  Forms two, identical daughter cells copyright cmassengale

Cytokinesis Cell Plate Forming in Plant Cells copyright cmassengale

Chromosomes & Karyotypes 24copyright cmassengale

Chromosomes 25copyright cmassengale

Chromosome Number All cells in the human body (SOMATIC CELLS) have 46 or 23 pairs of chromosomes Called the DIPLOID or 2n number GAMETES (eggs & sperm) have only 23 chromosomes Called the MONOPLOID or 1n number 26copyright cmassengale

Nondisjunction Chromosomes may fail to separate during meiosis Resulting gametes may have too few or too many chromosomes Disorders: – Down Syndrome – three 21 st chromosomes – Turner Syndrome – single X chromosome – Klinefelter’s Syndrome – XXY chromosomes 27copyright cmassengale

Normal Male 28 2n = 46 copyright cmassengale

Normal Female 29 2n = 46 copyright cmassengale

Male, Trisomy 21 (Down’s) 30 2n = 47 copyright cmassengale

Female Down’s Syndrome 31 2n = 47 copyright cmassengale

Klinefelter’s Syndrome 32 2n = 47 copyright cmassengale

Turner’s Syndrome 33 2n = 45 copyright cmassengale