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

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

3. 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

4. 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

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

6. 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

7. 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

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

10. 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

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

12. 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)

13. 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

14. 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

16. 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