Transcript CellReproduction

Cell Reproduction
Mitosis
Chromosomes
• Made of DNA
• Wrap around histone
proteins to become
chromatin
Chromosomes
• Chromatin wind up
further to become
chromosomes
• Each half of a
chromosome is a
chromatid
• Chromatids are held
together in the center
at the centromere
Chromosomes
• Sex chromosomes
determine an
organism’s sex
• Females = XX
• Males = XY
• Number of sex
chromosomes in a
human cell is 2
Chromosomes
• Autosomes – all the
chromosomes except
for the sex
chromosomes
• Number of autosomes
in humans = 44
Chromosomes
• Homologous
chromosomes – every
cell in sexual
organisms has two
copies of each
autosome
Chromosomes
• Humans have 44 autosomes so they have
22 homologous pairs.
• Dogs have 76 autosomes so they have 38
homologous pairs.
– Goat = 58
– Armidillo = 62
– Chicken = 78
– House fly = 12
– Mosquito = 6
Diploid
• Cells with 2 sets of
chromosomes
(homologous prs.) are
diploid.
• In humans, the diploid
number is 46 (2n)
Haploid
• Cells with one set of
chromosomes are
haploid.
• In humans, the
haploid number is 23
(1n).
Cell Division -Prokaryotes
• Bacteria do not have
a nucleus.
• They divided by a
process known as
binary fission.
Binary Fission
• Chromosomes
replicate
• The cell grows to
twice its original size
• The cell divides into
two identical cells
Cell Division in Eukaryotes
• Eukaryotes have a
nucleus in their cells
• Mitosis: results in new
cells with identical
genetic material
• Meiosis: results in
new cells with half the
number of
chromosomes
Cell Cycle
• Set of events that
make up the life of a
cell
Interphase
• Takes up most of the
cell’s lifespan (up to
90%)
Interphase
• G1 phase – cell
grows to mature size
• S phase – DNA
replication
• G2 phase – cell
prepares for division
Mitotic Phase
• Series of events that
allows a cell to divide
• Prophase
• Metaphase
• Anaphase
• Telophase
Prophase
• DNA winds up into
chromosomes
• Centrioles appear at
opposite ends of the
nucleus
Prophase
• Spindle fibers form
• Chromosomes attach
to spindle fibers
• Nuclear membrane
and nucleolus
disappear
Metaphase
• Chromosomes move
to the center
(equator) of the cell
Anaphase
• Chromatids separate
by the centromere
• They are now
considered to be
individual
chromosomes
Telophase
• Spindle fibers
disappear
• Chromosomes begin
to unwind into
chromatin
• Nuclear membranes
begin to form
Cytokinesis
• Immediately follows
mitotic division
• The cell membrane is
split in half
Animal Cytokinesis
• The membrane
pinches off into two
new cells
Plant Cytokinesis
• A cell plate forms in
the center.
• The plate separates
the two cells.