Download Cell Division - Biology 2013-14

Cell Division
Cell Cycle, Mitosis, & Meiosis
A. Why must cells divide?
1.
2.
Growth of multicellular organisms
a. Cells are limited by ratio of surface
area to volume because:
i. ______and____ can’t move in
and be transported through the
cell fast enough
ii. ______ and ____ can’t be
removed quickly enough
Replacement - e.g. ________
3.
4.
Repair of damaged tissue
Reproduction
a. Single celled life forms reproduce by
process called ___________ (asexual)
b. Multi-celled organisms
i. Sea star can reproduce by
part of its body breaking off
(asexual)
ii. Meiosis – formation of ________ (egg
and sperm)
iii. DM reproduce asexually or sexually
B. Important facts: It’s in the
chromosomes!
1.
2.
3.
4.
Chromosomes are made of _____coiled
around_____(Fig. 8-1)
Each chromosome has thousands of _______
Organisms have a certain number of
chromosomes (Humans have 46; cows have
60; cats have 32)
Chromosomes come in ______ ______
a. One of each pair comes from each parent
b. Homologous chromosomes code for the
same traits (hair color, digestive enzymes,
etc.)
5.
6.
7.
Sex chromosomes vs. Autosomes
a.
Sex chromosomes determine gender, but also code
for other traits ( in humans X & Y)
b.
The rest of the chromosomes are _________
Diploid (2N) = 46 in humans
a.
Full set of chromosomes
b.
Somatic cells (exs._______________)
c.
____________ is a picture of full set of
chromosomes (fig. 8-3)
Haploid (1N) = 23 in humans
a.
Half set of chromosomes
b.
______ & ______ cells
C. Cell Cycle
1.
2.
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Interphase + _______(fig. 8-5)
Interphase
a. Not part of mitosis
b. Normal functions of cell (exs._________)
c. DNA is replicated in preparation for mitosis
so each new cell can have a complete set of
chromosomes
i. Chromatids formed, but remain attached
at ___________ (fig. 8-2)
ii. Centromere is unreplicated part of DNA
3.
Mitosis (fig. 8-6)
a.
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Prophase (pro=first)
i. Chromatin (chromosomes & proteins)
shortens and thickens; can be seen with
microscope
ii. Each chromosome is made up of 2
identical _____
iii. Nuclear membrane & nucleolus
disintegrate
iv. Centrioles (animal cells only) move to
opposite poles of cell
v. _________ appear; these guide
chromosomes when they separate later
b.
Metaphase (meta=mid)
i. Chromatids position at ________ of
cell
ii. Order appears random in contrast to
meiosis
iii. Spindle fibers are attached to
centromeres
iv. Shortest phase
c.
Anaphase (ana = opposite)
i. Centromeres _______
ii. Chromatids separate to become
individual chromosomes
iii. Chr. move to opposite poles of cell
Telophase (telo = end)
d.
i.
ii.
iii.
iv.
Chromosomes lengthen and narrow, thus
become hard to see
Nucleolus reappears
Nuclear membrane reforms
Cytokinesis – dividing of __________


Animal cells - cytoplasm pinches together at
equator (fig. 8-7)
Plant cells – _________ forms (fig. 8-8)
Cellsalive.com
4.
Significance of mitosis
a.
b.
c.
Forms 2 cells __________ to parent cell
Cells are called _______ cells (mother cell
no longer exists)
Mitosis is a way of increasing the number of
cells without changing the _______
D. Meiosis
1.
2.
Meiosis is a ________ division because
it reduces the number of chromosomes
from diploid to haploid (46 23)
Forms cells needed for sexual
reproduction called _________
a. Spermatogenesis produces sperm
b. Oogenesis produces _____or eggs
3.
Stages of meiosis I (fig 8-9, P.154)
Prophase I
a.
i.
ii.
iii.
Metaphase I
b.
i.
Tetrads line up at equator
Anaphase I
c.
i.
d.
Synapsis = pairing of homologous chromosomes
Pairs called _______
Crossing over may occur (fig. 8-10) which
results in genetic mixing of chromosomes
Homologues separate
Telophase I
2 Cells; both are ___________
4.
Stages of Meiosis II (fig. 8-11, P.155)
a.
b.
c.
d.
Prophase II
Metaphase II – looks like metaphase of
mitosis
Anaphase II
Telophase II
5.
Significance of meiosis
Produces 4 haploid cells from 1 diploid cell
Sexual reproduction allows for genetic
variation of offspring (young)
a.
b.
i.
ii.
iii.
iv.
Combines chromosomes from both parents at
fertilization/conception
Crossing over in meiosis further mixes those
genes for more variation
Independent or random assortment of homologs
in __________(I) means offspring will get some
genes from each grandparent.
Variation helps species ______to changing
environment