Sources of Genetic Variation Mitosis vs. meiosis Sources of Genetic Variation

Mitosis vs. meiosis

mitosis ASEXUAL REPRODUCTION Makes BODY CELLS Makes 2 CELLS Daughter Cells Are GENETICALLY IDENTICAL to the parent - CLONES Makes DIPLOID Cells Advantage – FAST Disadvantage – LACK OF GENETIC VARIATION!!

meiosis SEXUAL REPRODUCTION Makes SEX CELLS Makes 4 CELLS Daughter Cells are GENETICALLY DIFFERENT from the parent Makes HAPLOID Cells Advantage – GENETIC VARIATION!! Disadvantage – LONG TIME

Attaches to the Spindle Fibers Sister Chromatids Attaches to the Spindle Fibers

SOURCES OF GENETIC VARIATION MEIOSIS – we just talked about this Crossing Over – when parts of chromosomes TOUCH and CHANGE genetic material during Prophase 1 in meiosis This is how mothers produce different eggs and how fathers produce different sperm

SOURCES OF GENETIC VARIATION Genetic Recombination – 2 different cells (sperm & egg) must join together in order to make a new individual Meiosis Mitosis

Non-Disjunction When chromosomes fail to SEPARATE PROPERLY during meiosis Produces sperm and eggs that have an ABNORMAL number of chromosomes They should always have 23 This commonly leads to DOWN SYNDROME – when a child is born with 3 copies of chromosome 21 Called a trisomy-21

Downs syndrome