Gene Expression

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Gene Expression

• Dr.Timmel

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Vocabulary

• To truly understand how our genes and environment
  affect who we are, we first need to understand
  some content specific vocabulary.
• You should commit these terms to memory!

• Be like the elephant, and never forget!

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Genome The complete genetic material of an
organism. It can be either DNA or RNA. In
humans, our genome is approximately 3,000,000,000
base pairs long!Human Genome Project
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Gene A segment of a chromosome which codes for
one specific protein or trait.Allele The term
used to describe different versions of the same
gene. For example the blue eye or brown eye
allele.
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Chromatin Mass of genetic material composed of
DNA and proteins that condense to form
chromosomes in eukaryotic cell division.
Chromatin is located in the cell's nucleus.
Chromatin consists of long, thin strands that
cannot be seen with a compound light
microscope.Memory aid Chromatin is thin.
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Chromosome Long, stringy aggregates of genes
that carry heredity information and are formed
from condensed chromatin. These become visible
under a compound light microscope just prior to
cell division.
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Chromatid One of the two identical parts of the
chromosome. The two chromatids of a single
chromosome are called sister chromatids.Centrome
re The centromere is the constricted point at
which the two chromatids forming the chromosome
are joined together.
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What does a chromosome look like?
1 chromatid
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Genotype The genetic constitution (the genome)
of a cell, an individual or an organism. The
genotype is all of the genes within your cells.
Only identical twins (or tripets, etc.) have
the same genotype.
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Phenotype The observable physical or
biochemical characteristics of an organism, as
determined by both genetic makeup and
environmental influences.Genotype Environment
Phenotype.
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The snowshoe hare. The appearance of this animal
changes as the environmental conditions change.
The genotype is always the same.
Winter Spring Summer
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Does the environment affect human phenotypes?

• Absolutely! Light skinned people generally are
  paler during the winter months. However, in the
  summer when they are outside and exposed to more
  ultra violet radiation, they tan.
• Some diseases also result from a change in
  environmental conditions. If your body is
  lacking in vitamin C, you can get the disease
  called scurvy.
• As a result, the shape of the long bones in your
  arms and legs can become curved.

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In conclusion

• Our outward appearance, or phenotype is
  determined as much by our environment as it is
  our genotype.
• Our genotype never changes, though our phenotype
  does change over time.
• except in the case of a mutation.