Ch. 9 Cell Division and Mitosis
9.1 Dividing Cells
Where in the cell are
chromosomes located?
I. Two types of nuclear
division:
A. Mitosis- creates more somatic cells
(body cells) for growth, development
and repair in multicellular organisms
and asexual reproduction in some
organisms.
B. Meiosis- creates gametes (sperm or
egg cells) for sexual reproduction
Germ cells-cells which produce gametes
A chromosome is made of
DNA and protein.
•  Chromatinunorganized
DNA, in nucleus
when cell is not
dividing
•  DNA duplicates
before division.
DNA wraps around proteins to
make chromosomes.
Gene- a segment of DNA on a
chromosome
II. Chromosome Number
A. Karyotype-picture of all the
chromosomes in one cell
•  There are 46
chromosomes
(23 pairs) in a
human body
cell = Diploid=
2n
Chromosome number of some
species:
•  # Hare 46
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# Hedgehog Genus Atelerix (African hedgehogs) 90
# Hedgehog Genus Erinaceus (Woodland hedgehogs) 88
# Horse 64
# Human 46, with 44 autosomal and 2 sexual
# Hyena 40
# Ichthyomys pittieri (semiaquatic rodent) 94 [highest for a mammal]
# Kangaroo 12
# Kit Fox 50
# Long-nosed Cusimanse (a type of mongoose) 36
# Maize 20
# Maned Wolf 76
# Meerkat 36
# Mosquito 6
# Mouse 40
There are 23
chromosomes
in human sex
cells (egg or
sperm)=
Haploid= 1n
Human life cycle
9.2 The Cell Cycle
Why does DNA replicate
before mitosis?