Chromosomes
Chromosomes contain all of our genetic
information.
CHROMOSOMES contain GENES which
are made from DNA.
Humans have 23 PAIRS OF
CHROMOSOMES.
These chromosomes are the
INSTRUCTIONS FOR EVERYTHING in
our body.
Chromosome Maps and Gene Maps
Autosomal Genetic Disorders – Down
Syndrome
Sex-Linked Genetic Disorders
Mitosis
MITOSIS
2N
2N
2N
ALL CELLS AND DNA IDENTICAL
Mitosis

Occurs in Somatic
(body) cells

Used in growth &
repair of body cells,
Asexual reproduction
Cells will turn into this
 Daughter
cells will turn
into fully functional
body cells (liver cells,
muscle cells, etc.)
Meiosis
2N
Division I
Division II
1N
1N
1N
1N
4 NEW GENETICALLY DIFFERENT CELLS
Meiosis
Meiosis

Occurs in Gametes
(sex cells)

Used in Sexual
reproduction
Sperm and Egg Meiosis
Cells will turn into this
 Males
– 4 sperm
 Females – 1 egg and 3 polar bodies
Chromosome Number

Divides in half (46 to 23
chromosomes)

Sperm (23) and egg (23) combine to
form a zygote (46) during
fertilization

This ensures chromosome # is right
Genetic material
 Genetic
Variation
caused by crossing
over – chromatids
overlap, break
apart, and
reattach to form
new combinations
of DNA
Mitosis
Meiosis
Purpose
Growth,Repair
Sexual
Reproduction
Chromosome #
2N to 2N
2N to 1N
# of cells
produced
# of divisions
2
4
1
2
Genetic
Stays the same
Material
Where it occurs Somatic cells
Variation in
gametes
Gametes