Transcript Meiosis and Reproduction

Meiosis and Reproduction
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Meiosis
Fertilization
Development
Natural Selection
Genetics Review
Larry M. Frolich, Ph.D.
Biology Department, Yavapai College
How are genetic traits combined and
passed on from parent to offspring
• Meiosis produces gametes or sex cells
(eggs and sperm) with just one member of
each chromosome pair
• Fertilization results in union of female
gamete (egg) with male gamete (sperm)
• Subsequent embryonic, fetal and
embryonic development by mitosis and
differentiation of cell types produces new
individual
Larry M. Frolich, Ph.D.
Biology Department, Yavapai College
Larry M. Frolich, Ph.D.
Biology Department, Yavapai College
Larry M. Frolich, Ph.D.
Biology Department, Yavapai College
18.3 Meiosis
Overview of meiosis
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Two nuclear divisions
occur to make 4 haploid
cells (cells with just one
member of each
chromosome pair)
Meiosis results in
gametes (egg and
sperm)
Has 8 phases (4 in each
meiosis I & II)
Larry M. Frolich, Ph.D.
Biology Department, Yavapai College
Larry M. Frolich, Ph.D.
Biology Department, Yavapai College
Table 18.2
Larry M. Frolich, Ph.D.
Biology Department, Yavapai College
Alleles
• A particular gene, or protein-coding region of
DNA along a chromosome might have a few
different variations, called alleles
• The combination of alleles, at a particular
gene, or chromosome region, that you get
from your mother and father determine your
hereditary traits
• Please do the Dragon Genetics lab to
understand this
Larry M. Frolich, Ph.D.
Biology Department, Yavapai College
Fertilization
• After meiosis, male and female gametes (sperm and
egg) unite to form a new cell—a zygote—that has the
full set of 23 pairs of chromosomes (in humans).
Larry M. Frolich, Ph.D.
Biology Department, Yavapai College
Embryonic development—mitosis produces tissues/structures of adult
Larry M. Frolich, Ph.D.
Biology Department, Yavapai College
Larry M. Frolich, Ph.D.
Biology Department, Yavapai College
Some adult
features are coded
for genetically in
alleles or gene
varieties of sperm
and egg
Be sure to see
sickle cell
anemia
example in this
section of the
course
Larry M. Frolich, Ph.D.
Biology Department, Yavapai College
Inheritance and Natural Selection
• Some combinations of alleles, produced during meiosis
and fertilization might be more advantageous
• This is what leads to natural selection. Individuals with
more advantageous traits will survive to reproduce and
pass on those traits.
• Darwin realized that slow changes in inherited traits, due
to natural selection produced the great evolutinoary
history of life.
• Before his synthesis of all the evidence, no one could
make sense of living systems. Now, “Nothing in Biology
Makes Sense Except in the Light of Evolution”
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--Theodosius Dobzhansky
Please do the Coyote Lab to see how meiosis, fertilization,
inheritance and natural selection all work together to produce the
gradual change in biological organisms that we call evolution.
Larry M. Frolich, Ph.D.
Biology Department, Yavapai College
GENETICS (review)
• Cells divide and pass on
instructions coded in DNA of
chromosomes
• Each chromosome is a huge DNA
molecule with coded information
– DNA replicates to pass on information
– DNA is transcribed to make proteins
that run cell metabolism
• Cancer—example of what happens
when genetic control goes awry
• Normal inheritance and meiosis
Larry M. Frolich, Ph.D.
Biology Department, Yavapai College
DNA and chromosomes
• Long DNA molecules (millions
of base pairs long) in nucleus
are called chromosomes
• Each chromosome is organized
and packaged or wrapped up
with proteins giving it a certain
shape
• In humans, 23 pairs of
chromosomes
– 1 of each pair from mother
– 1 of each pair from father
• Total view of all 23 pairs is
called karyotype
Larry M. Frolich, Ph.D.
Biology Department, Yavapai College
Mitosis—what happens (overview)
• DNA/chrosomes replicate
(make exact copies
• Copies line up at center
of cell
• Copies pulled to opposite
ends of cells by
centromeres/spindles
• Cell membrane pinches
off and splits cell into two
Larry M. Frolich, Ph.D.
Biology Department, Yavapai College
Mitosis—constant, fast,
keeps body functioning
• Remember, mitosis produces two identical
daughter cells
• Mitosis is constantly happening in your body
to allow for growth, replacement and repair
• While you read this slide, millions of new
cells were produced by mitosis in the tissues
of your body!
• Don’t forget cellular scale and intelligence—
it’s a whole planet happening at the submicroscopic level
Larry M. Frolich, Ph.D.
Biology Department, Yavapai College
DNA is structured to replicate
• DNA is “double helix”—
two complementary
strands wound in a spiral
• Strands separate and
DNA replicates by filling
in other half of each
separated strand
• Famous Watson-Crick
model (Nobel prize)
Larry M. Frolich, Ph.D.
Biology Department, Yavapai College
DNA is transcribed to make proteins
that run cell metabolism
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DNA is transcribed to mRNA
mRNA is translated to amino acid sequence
Amino acid sequence folds up into protein
Proteins catalyze reactions of cell metabolism
This process is called “gene expression”—the
information in one region of the DNA—a
“gene”—is being expressed so that the cell’s
metabolism can function
Larry M. Frolich, Ph.D.
Biology Department, Yavapai College
Overview of transcription and translation
REMEMBER: A particular region of DNA that has the code to make a particular protein is called a “gene.”
Details in web link video animations
Larry M. Frolich, Ph.D.
Biology Department, Yavapai College
Regulation of gene expression
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Gene expression is regulated—not all genes are
constantly active and having their protein produced
The regulation or feedback on gene expression is
how the cell’s metabolism is controlled.
This regulation can happen in different ways:
1. Transcriptional control (in nucleus):
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e.g. chromatin density and transcription factors
2. Posttranscriptional control (nucleus)
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e.g. mRNA processing
3. Translational control (cytoplasm)
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e.g. Differential ability of mRNA to bind ribosomes
4. Posttranslational control (cytoplasm)
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e.g. changes to the protein to make it functional
When regulation of gene expression goes wrong—
cancer!
Larry M. Frolich, Ph.D.
Biology Department, Yavapai College
How are genetic traits combined and
passed on from parent to offspring
• Meiosis produces gametes or sex cells
(eggs and sperm) with just one member of
each chromosome pair
• Fertilization results in union of female
gamete (egg) with male gamete (sperm)
• Subsequent embryonic, fetal and
embryonic development by mitosis and
differentiation of cell types produces new
individual
Larry M. Frolich, Ph.D.
Biology Department, Yavapai College
Fertilization
• After meiosis, male and female gametes (sperm and
egg) unite to form a new cell—a zygote—that has the
full set of 23 pairs of chromosomes.
Larry M. Frolich, Ph.D.
Biology Department, Yavapai College
Inheritance and Natural Selection
• Some combinations of alleles, produced during meiosis
and fertilization might be more advantageous
• This is what leads to natural selection. Individuals with
more advantageous traits will survive to reproduce and
pass on those traits.
• Darwin realized that slow changes in inherited traits, due
to natural selection produced the great evolutinoary
history of life.
• Before his synthesis of all the evidence, no one could
make sense of living systems. Now, “Nothing in Biology
Makes Sense Except in the Light of Evolution”
•
--Theodosius Dobzhansky
Please do the Coyote Lab to see how meiosis, fertilization,
inheritance and natural selection all work together to produce the
gradual change in biological organisms that we call evolution.
You can download this lab from the Online Lab links for this
section of the course.
Larry M. Frolich, Ph.D.
Biology Department, Yavapai College