Download Chapter 8 Cell Reproduction

Section 1 Chromosomes


Chromosomerod-shaped
structure made
of DNA and
proteins
If DNA were
stretched out,
it would be 6
feet long!!
How does it fit into the nucleus of a
cell?
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The red structures are
histone proteins
DNA is tightly
coiled around
histone proteins
*These proteins
help maintain the
shape of
chromosomes

DNA molecules are coiled on many levels to
form chromosomes

Chromatid-each identical half of a
chromosome

-less tightly coiled DNA; DNA exists as
chromatin when it is not coiled into
chromosomes

…is a circle and consists of one chromosome
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How many do we
have?
46 chromosomes
Or 23 pairs of chromosomes
Organism
Number of
Chromosomes
Adder’s tongue 1,262
fern
Organism
Number of
Chromosomes
Garden pea
20
Carrot
18
Gorilla
48
Cat
32
Horse
64
Chimpanzee
48
Human
46
Dog
78
Earthworm
36
Lettuce
18
Orangutan
48
Fruit fly

8
Does the number of chromosomes indicate
the complexity of an organism?
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We have 1 pair or 2 chromosomes
They are X and Y
XX
XY
1. Sex Chromosomes-chromosomes that
determine the sex of an individual
2. Autosomes-They control everything about
us except for our sex
Ex. Eye color
We have 22 pairs or
44 autosomes

Two
Chromosomes
similar in size
and shape
that make up a
pair are called
Homologous
chromosomes
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Do you see the
autosomes?
Do you see the
sex
chromosomes?
Which one is
male and
which one is
female?
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is called a karyotype
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Missing parts of chromosomes
Extra chromosomes
Sex of offspring
Down Syndrome-caused
by 3 chromosomes
#21
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Diploid- a full set of chromosomes from both
parents (2n)
Haploid- one set of chromosomes (1n)
Egg and sperm
cells are haploid;
all other cells are
diploid


25 million cells
are produced by
an adult human
body every day
Growth and
development are
achieved by cell
division

Binary fission- the division of a prokaryotic
cell into two offspring cells


Results in two identical cells from a parent
cell
Occurs for development, cell repair, or
asexual reproduction

Allows chromosome number to be reduced to
half. In us, 23 chromosomes are contained
in our sex cells
Meiosis produces
gametes which are sex
cells

Includes interphase, mitosis and cytokinesis
Interphase- a cell spends most its time
in interphase
G1- offspring cells grow to mature
size
S- DNA is copied (synthesized)
G2- cell prepares to divide

Mitosis
Prophase
Metaphase
Anaphase
Telophase
1
2
prophase
3
telophase
4
metaphase
5
What type of cell
is shown; plant
or animal? How
do you know?
interphase
anaphase
Cytokinesis- the division
of the cytoplasm and
organelles; begins with a
cleavage furrow in animal
cells and a cell plate in
cell walls