Cell division to cut the number of chromosomes in 1/2 Meiosis Cell division to cut the number of chromosomes in 1/2

I. Somatic cells A) normal cells in body B) have 2 copies of each gene ( 1 from mom, 1 from dad) C) called diploid cells D) abbreviated 2n

II. Homologous Chromosomes A. look the same size shape banding pattern B. code for the same traits (height) C. can have different version of trait ( tall or short) D you get 1 from mom and the other from dad

Iii. karyotypes A) Type of chromosomes in the nucleus B) Should be 2 of each kind 1 from Mom 1 from Dad C) If NOT 2 of each = chromosome mutation

IV. Chromosome Mutation A) Too Many or too few chromosomes B) Can cause 1) embryo to die 2) genetic disorders

V. Two Types of chromosome A) Sex Chromosomes 1) XX for female 2) Xy for male B) Autosome 1) all the other chromosomes 2) we all automatically get these

VI. Trisomy = 3 copies of an autosome A) almost always fatal (miscarriage = embryo dies) B) 2 cases infants born with microcephaly or other major defects 1) trisomy 18 & trisomy 13 2) neonatal ICU only live a few days 3) few live 1 year, very few to teens

C) only trisomy 21 has long life expectancy 1) Down syndrome 2) cognitive impairment 3) Characteristic physical deformities

vIi. Gametes A. Sex cells……not somatic (body) cells B. Gametes 1. have only 1 copy of each chromosome 2. so called 1n 3. or haploid (½ the chromosomes of normal somatic cell) C. Gametes = eggs or sperm

Somatic cell (body cell) Gamete (egg/sperm)

viiI. Meiosis A. Nuclear division to make gametes B. Meiosis I : get 1 of each chromosome in each daughter cell C. Meiosis II : split x shape into single chromatids D. Makes 4 new cells (gametes)

iX.Compare & Contrast Meiosis & Mitosis Mitosis (makes cells that are) Meiosis (makes cells that are) identical daughters Same # chromosomes 2n ….diploid cells Called somatic cells Makes different cells ½ number of chromosomes 1n……haploid cells Called gametes

Different Processes Mitosis Meiosis Divides 1 time Makes 2 identical cells No genetic variation Asexual reproduction Divides twice Makes 4 cells (all different) Causes genetic variation Sexual reproduction

x. Who does meiosis? A) only Eukaryotes (prokaryotes don’t have a nucleus) B) plants & animals do meiosis to make gametes C) some Fungi and Protists also do meiosis