Unit 5: Cellular & Organismal Reproduction
Topic 1: The Cell Cycle
Cell reproduction
• How do cells reproduce?
They divide into two cells!
First they copy all their parts (DNA, organelles, ribosomes)
• When does a cell reproduce?
When a multicellular organism is growing or needs to
replace dead or damaged cells (mitosis)
To make gametes for sexual reproduction in eukaryotes
(meiosis)
When a single-celled organism reproduces asexually
(mitosis or binary fission)
Some Definitions
• Parent Cell
• Daughter Cell
• Sexual
Reproduction
– Variation
• Asexual
Reproduction
3
Asexual reproduction in bacteria
(binary fission)
Figure 8.3A, p127
Binary
Fission
4
Other forms of asexual reproduction
•
•
•
•
Budding
Fragmentation
Regeneration
Advantages:
– Don’t need to
search for a mate
– Can reproduce if
damaged
• Disadvantage:
– No recombination
of genetic material
Chromatin
6
7
Fun facts: number of chromosomes in a variety of organisms
Species
Humans
Kangaroo
Cat
Cow
Dog
Turkey
Algae
Shrimp
Ophioglossum reticulatum
(fern)
# chromosomes
46
12
38
60
78
82
148
254
~1200! (highest
UNreplicated
Chromosome
Replicated
Chromosome
Sister
Chromatids
UNreplicated
Chromosomes
Figure 8.4, p128
10
Chromosome Anatomy
11
Homologous chromosomes
• Each chromosome has a
homologue, or a
chromosome that carries
the same type of
information as another
chromosome
• The chromosomes may
have different versions
of the genes but the
genes code for the same
type of information
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Cell cycle
Figure 8.5, p129
13
Mitosis inquiry
Cell cycle
Figure 8.5, p129
15
The stages of mitotic cell division in an animal cell:
G2 phase; prophase; prometaphase
Figure 8.6, p130
16
The stages of mitotic cell division in an animal cell:
metaphase; anaphase; telophase and cytokinesis.
Figure 8.6, p131
17
Mitosis
18
Mitosis in an onion root
19
Cytokinesis in animal and plant cells
Figure 8.7, p132
20
Cell turnover
• The length of a cell cycle
depends on the type of
cell and its function in
the body.
• Some cells never divide
after the first few months
of life: brain, nerves
• Some cells never divide
at all: red blood cells
• Some divide every 20
hours or so: cells of
organ linings and skin
cells
Chromosomes
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