Development: differentiating cells to become an organism

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Development differentiating cells to become an
organism
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Cells function differently because they express
differentgenes.
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The proper control of gene expression is critical
for proper development.
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Inverse relationship between smoking and weight
more smoking less weight
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Effect of smoking on fetal development and how
that can affect adults
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Adults exposed to smoke as fetuses have higher
risk of obesity and heart disease
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What is the connection?
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Obesity, Diabetes, Heart Disease, High Blood
Pressure, Some Cancers all may have some origins
during fetal development.
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Adults metabolism may react to poor nutrition as
fetuses Adaptation of Thriftiness or Catch Up
Growth.
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Adults metabolism may react to poor nutrition as
fetusesAdaptation of Thriftiness or Catch Up
Growth. Study of babies born during Dutch famine
of 1944-45
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Adults metabolism may react to poor nutrition as
fetusesAdaptation of Thriftiness or Catch Up
Growth. Study of babies born during Dutch famine
of 1944-45 20 years later found that these
babies had higher rates of obesity.
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Adults metabolism may react to poor nutrition as
fetusesAdaptation of Thriftiness or Catch Up
Growth. Study of babies born during Dutch famine
of 1944-45 20 years later found that these
babies had higher rates of obesity. Precise
mechanism is not known
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What about smoking? 17,000 births studied and
checked at age 16 and 33. Fetuses exposed to
smoking had increased rate of obesity.
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What about smoking? 17,000 births studied and
checked at age 16 and 33. Fetuses exposed to
smoking had increased rate of obesity and more
smoking meant more obesity.
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What about smoking? 17,000 births studied and
checked at age 16 and 33. Fetuses exposed to
smoking had increased rate of obesity and more
smoking meant more obesity. For Moms who
abstained during pregnancy, no effect on fetus or
as adult.
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What about smoking? 17,000 births studied and
checked at age 16 and 33. Fetuses exposed to
smoking had increased rate of obesity and more
smoking meant more obesity. Smoking during first
trimester had same effect as during whole
pregnancy.
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What about smoking? For diabetes more than 10
cigarettes per day gave a 4 times greater risk of
diabetes.
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What about smoking? Risk of high blood pressure
also increases with increased exposure to fetus
of smoking during pregnancy
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Why?
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Why? Nicotine can inhibit hunger and increase
energy expenditure. This can lead to poor fetal
nutrition.
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Why? Nicotine causes constriction of blood
vessels, and may limit blood flow to the fetus.
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Mammalian circulation
AAL 38.8
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Nicotine causes blood vessels to constrict
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Why? CO in blood decreases delivery of O2 to
fetus.
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Why? These are all indirect affects leading to
adaptation to thriftiness Nicotine can inhibit
hunger and increase energy expenditure. Nicotine
causes constriction of blood vessels, and may
limit blood flow to the fetus. CO in blood
decreases delivery of O2 to fetus.
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Why? Nicotine and other toxins in smoke may
directly affect hormones that direct fetal
development.
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Hormones are molecules produced in one cell and
signal another.
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Why? Nicotine and other toxins in smoke may
directly affect hormones that direct fetal
development. Including hormones that direct brain
development.
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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) Identical twins
reared together 80 Identical twins reared
apart 72 Fraternal twins reared
together 43 Biological siblings 34 Parents
and children living together 26 Adopted children
and parents 4 Unrelated children living
together 1
The nature of environmental influences on weight
and obesity A behavior genetic analysis. Grilo,
Carlos M. Pogue-Geile, Michael F. Psychological
Bulletin, Vol 110(3), Nov 1991. pp. 520-537. And
two books by Matt Ridley Nature via Nurture
(2003) and Genome the Autobiography of a
Species in 23 Chapters (1999)
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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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What happened during development?
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Fig 23.3
Developmental mutants of Drosophila melanogaster
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Fig 23.1
Increases in cell number play a role
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Fig 23.1
so does cell death.
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Development of a mouse paw yellow areas show
dying cells
CB 21.19
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Development in animals is one way. Why?
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Vertebrate Development from zygote to adult
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Fig 19.13
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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Why do cells lose totipotency?
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Why do cells lose totipotency?
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Mature, differentiated plant cells are totipotent
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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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Fig 10.21
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
Fig 3.8
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Fig 10.21
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. Often in the form of
DNA methylation
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Fig 19.13
Stem cells still have totipotency
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Embryonic Stem Cells are totipotent Adult Stem
Cells are pluripotent (only form some cell types)
Fig 19.14
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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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Fig 23.27
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All humans are female for the first nine weeks of
development
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Fig 23.23
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
Fig 23.24
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Fig 23.23
FrakenFlowers
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Changing expression of A, B, or C genes changes
organ identity
Fig 23.24
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Fig 23.23
4 whorls of a flower
Flower parts Complexity from a few simple genes