Development

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Development

• Homework 2 is due 10/17
• Bonus 1 is due 10/24

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So, Smoking during pregnancy may have indirect
and/or direct affects on fetal development, and
these affects may manifest themselves in adults.
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Correlation of weight and relatedness

• Correlation of weight (BMI)
• Biological siblings 34
• Parents and children living together 26
• Identical twins reared together 80
• Identical twins reared apart 72
• Fraternal twins reared together 43
• Adopted children and parents 4
• Unrelated children living together 1

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Nature and Nurture Are traits coded for by genes
fixed while traits coded for by the environment
are under our control?
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Developmental mutants of Drosophila melanogaster
Fig 12.1
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Vertebrate Development from zygote to adult
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Besides adding cells, development can involve
cell death.
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Development of a mouse paw yellow areas show
dying cells
CB 21.19
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Early embryo development
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Totipotent ability to differentiate into any
cell-type
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Totipotency is limited to early stages of animal
development
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Mature, differentiated plant cells are totipotent
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Why do cells lose totipotency?
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Why do cells lose totipotency?
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• Gene expression can be controlled at many points
  between DNA and making the final proteins.
• Changes in the various steps of gene expression
  control when and how much of a product are
  produced.

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• Why change gene expression?
• Different cells need different components
• Responding to the environment
• Replacement of damaged/worn-out parts

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DNA packaging fluctuatesgenes being expressed
are unpackaged, genes not needed are tightly
packaged.
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Normally DNA is loosely packaged
During mitosis DNA is tightly packaged as
chromosomes and individually visible
box 2.1
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DNA packaging fluctuatesSome of the tight
packaging of DNA is irreversible.
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Irreversible packaging of DNA partially explains
the loss of totipotency.
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Stem cells still have totipotency
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Embryonic Stem Cells are totipotent Adult Stem
Cells are pluripotent (only form some cell types)
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Developmental information can be encoded by both
genetic and non-genetic information.
Fig 12.2
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What genetic mechanisms regulate/allow
development?
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All humans are female for the first nine weeks of
development
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(No Transcript)
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All humans are female for the first nine weeks of
development
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Downs Syndrome is caused by an extra chromosome
21.
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Downs Syndrome is caused by an extra chromosome
21. Too much information disrupts normal
development.
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4 whorls of a flower
Flower parts Complexity from a few simple genes
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Each whorl expresses a specific combination of
three genes
CB 21.20
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Changing expression of A, B, or C genes changes
organ identity
CB 21.20
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Development

• Homework 2 is due 10/17
• Bonus 1 is due 10/24