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Yellow Pages Endeavour held the world sailing
speed record at 46 knots, 54 mph, set in 1993
at Sandy Point, MelbourneAustralia for 12 years.
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Learning goals Lecture 7, Mitosis and Meiosis
Text Reading Chapter 12, Overview, pp. 218 - 226
(stop at Binary Fission) also, Fig. 12.8
(chromosome movement) is not required. Chapter
13 (all).
You need to be able to explain the following to
yourself and to me (on exams)
Mitosis makes identical daughter cells Where it
occurs (functions) produces identical daughter
cells, cell cycle, stages (interphase, prophase,
prometaphase, metaphase, anaphase, telophase,
cytokinesis), sister chromatid
Meiosis makes haploid gametes sexual
reproduction, haploid, diploid, gamete,
homologous chromosome, the two stages of meiosis,
reductional division, independent assortment,
chiasma  
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Figure 12.2 The functions of cell division
Mitosis functions sister chromatids cell
cycle Stages cytokinesis
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Figure 12.4 Chromosome duplication and
distribution during cell division
Mitosis functions sister chromatids cell
cycle Stages cytokinesis
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Figure 12.5 The cell cycle
Mitosis functions sister chromatids cell
cycle Stages cytokinesis
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MITOSIS

• 1882 drawing of mitosis in a salamander embryo
  (Walther Flemming)
• Flemming observed that the threads were double,
  would eventually split
• Flemming was the first to use the word mitosis
• Greek mitos thread
• We now know that the threads are strands of DNA
  ( proteins) or chromosomes, called chromatin

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Figure 19.2 Levels of chromatin packing - just
know that it happens!
Mitosis functions sister chromatids cell
cycle stages cytokinesis
Metaphase in light microscope
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Figure 12.6 Exploring The Mitotic Division of an
Animal Cell
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Figure 12.6 Exploring The Mitotic Division of an
Animal Cell
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Terms to know about mitosis

• Chromatin - the combination of DNA and histone
  and other proteins that makes up chromosomes - it
  stains well in light microscopy
• Centromere - a constriction especially easily
  seen at metaphase, containing the area to which
  the spindle fibers attach.
• Kinetochore - the specific small part of the
  centromere to which the spindle fibers attach.
• Spindle fibers - microtubules of protein that can
  move chromosomes.
• Centrosome - the region that forms at opposite
  ends of the cell during mitosis, where the
  spindle fibers converge.
• Centriole - a small structure in the middle of
  the centrosome.
• Aster - a description of the centrosome growing
  spindle fibers - this looked to early cell
  biologists like a star, hence aster.
• Microtubule - fibers, made of proteins, that move
  chromosomes (among other things)

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Figure 12.9 Cytokinesis in animal and plant cells
Mitosis functions sister chromatids cell
cycle stages cytokinesis
Vesicle small membrane-lined bag
Daughter cells
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Mitoses in onion apical meristem (root tip)
?
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Mitoses in onion apical meristem (root tip)
?
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• Karyotypes are prepared with metaphase cells.

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Figure 13.2 The asexual reproduction of a hydra
Meiosis sexual reproduction haploid, diploid,
gamete homologous chromosome two stages of
meiosis independent assortment crossing-over
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Meiosis sexual reproduction haploid, diploid,
gamete homologous chromosome two stages of
meiosis independent assortment crossing-over
A fundamental problem - a paradox - for
genetics Heredity - like reproduces like,
but Variation - offspring are never exactly like
their parents Sexual reproduction and meiosis are
important parts of the resolution of this
paradox. Sexual reproduction means that special
reproductive cells, or gametes, are produced.
These fuse at fertilization (syngamy) to make a
zygote.
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Figure 13.5 The human life cycleHaploid means
that the cell has a single complete genome, and
one of each chromosome (n). Diploid means that a
cell has two complete genomes, and two of each
chromosome (2n).exceptions later
Meiosis sexual reproduction haploid, diploid,
gamete homologous chromosome two stages of
meiosis independent assortment crossing-over
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Figure 13.6 Three types of sexual life cycles
Meiosis sexual reproduction haploid, diploid,
gamete homologous chromosome two stages of
meiosis independent assortment crossing-over
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Figure 13.4 Describing chromosomes in a diploid
cell at metaphase - in a eukaryote
Meiosis sexual reproduction haploid, diploid,
gamete homologous chromosome two stages of
meiosis independent assortment crossing-over
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Meiosis sexual reproduction haploid, diploid,
gamete homologous chromosome two stages of
meiosis independent assortment crossing-over
Why do we bother with coloring the chromosomes
from mom and dad differently? Because they could
have slightly different versions of genes - they
could vary. Ultimately, variation is due to
mutation, but we are getting ahead of ourselves.
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Figure 13.7 Overview of meiosis how meiosis
reduces chromosome number - only one round of
chromosome (DNA) replication, but two meioitic
divisions of the homologs and sister chromatids.
Meiosis sexual reproduction haploid, diploid,
gamete homologous chromosome two stages of
meiosis independent assortment crossing-over
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Figure 13.8 The Meiotic Division of an Animal Cell
Meiosis two stages of meiosis
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Figure 13.8 The Meiotic Division of an Animal Cell
Meiosis two stages of meiosis
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Figure 13.9 A comparison of mitosis and meiosis
Meiosis sexual reproduction haploid, diploid,
gamete homologous chromosome two stages of
meiosis independent assortment crossing-over
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Figure 13.10 The independent assortment of
homologous chromosomes in meiosis
Meiosis sexual reproduction haploid, diploid,
gamete homologous chromosome two stages of
meiosis independent assortment crossing-over
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How many possible combinations?

• The number of possible new combinations of
  chromosomes for a species is 2n
• n haploid number of chromosomes for the species
• Fruit fly 24
• Humans 223
• Dog 239

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Figure 13.11 The results of crossing over during
meiosis
Meiosis sexual reproduction haploid, diploid,
gamete homologous chromosome two stages of
meiosis independent assortment crossing-over
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A mammalian egg with many sperm trying to
fertilize it (only one will succeed).
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Spermatogenesis. Generally the objective is to
produce as many small haploid sperm as possible.
In human males about 150 million sperm cells are
produced every day, that is about 1700 every
second! Likely result of sperm competition, where
females mate with more than one male within hours
of each other and their sperm compete to
fertilize her egg.
Meiosis I, Cytoplasmic Division
Meiosis II, Cytoplasmic Division
Growth
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The generality of massive sperm production and
competition in males is not universal. This is a
single coiled up spermatozoon of Drosophila
bifurca. It is 6 cm long. Males produce about 100
total, and take 17 days to mature to these sperm,
compared with mm long sperm.
Human sperm are 25 µm
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Oogenesis. The objective is to produce large eggs
carrying the materials needed for survival and
early development of the coming embryo. There is
ongoing controversy about whether oocytes
continue to be produced in adulthood, with some
evidence for it in mice, but not yet for humans.
first polar body (haploid)
three polar bodies (haploid)
primary oocyte (diploid)
oogonium (diploid)
secondary oocyte (haploid)
ovum (haploid)
Meiosis I, Cytoplasmic Division
Meiosis II, Cytoplasmic Division
Growth
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Origins of mutations A consequence of this
general distinction between males and females in
both animals and plants is that most novel simple
mutations like a single base change, perhaps
causing a single amino acid change, occur in male
germlines, simply because each stem cell
undergoes many mitoses to produce the many
spermatocytes, each of which yield four sperm.
Females. In humans it is particularly striking,
because any ovum from a woman of any age has
undergone only about 30 cell divisions since she
was a single cell zygote. At birth women have
about 1 million eggs held in arrested expectancy,
yet use only 12 per year (20,000 die per
year). A numeric example if the mutation rate
caused by DNA polymerase is 1 error per 1010 base
pairs copied, and the genome is 3 X 109 base
pairs, then 30 divisions will yield just 10
single base changes per ovum, and since 95
percent of our DNA is non-coding and
non-conserved, at most one of these will change
one amino acid in one of our 30,000 proteins.
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Males. In contrast, each sperm produced by a
30-year-old male has undergone about 400 cell
divisions since the zygote stage, and that of a
60-year-old male perhaps 1000 cell divisions.
As a result the frequency of mutations in male
sperm should be about 10-50 fold higher, with
several amino-acid-changing mutations per sperm.
Although it has not yet been possible to examine
these directly, in some unusual cases it is
possible to determine in which parent a novel
mutation occurred, and in over one hundred such
cases analysed to date, every time it was in the
father. Therefore, men contribute most
mutations in evolution and genetic diseases.
Recent molecular evolution studies confirm that
the excess of mutations from fathers is between
5X and 20X.
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Learning goals Lecture 7, Mitosis and Meiosis
Text Reading Chapter 12, Overview, pp. 218 - 226
(stop at Binary Fission) also, Fig. 12.8
(chromosome movement) is not required. Chapter
13 (all).
You need to be able to explain the following to
yourself and to me (on exams)
Mitosis makes identical daughter cells Where it
occurs (functions) produces identical daughter
cells, cell cycle, stages (interphase, prophase,
prometaphase, metaphase, anaphase, telophase,
cytokinesis), sister chromatid
Meiosis makes haploid gametes sexual
reproduction, haploid, diploid, gamete,
homologous chromosome, the two stages of meiosis,
reductional division, independent assortment,
chiasma