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dominant trait is expressed, but Human Genetics
not fully.
Genetic disorders. Left to right: a
man with Down Syndrome, and a
girl with cystic fibrosis.
Peas are great, but what does
genetics have to do with me? What
does genetics have to say about
human beings? A lot, actually.
Pink Snapdragon Flower. Mendel’s laws help us study the
Incomplete dominance in action! various genetic disorders (such
Another exception is when there as Down Syndrome, and Cystic
are two different types of dominant Fibrosis) that affect humans. A
alleles which are both expressed. genetic disorder is simply a disease
This is called codominance. For or disorder that is inherited
example the AB bloodtype carries genetically. Genetic disorders can
traits of both the A and B blood be caused by single defective gene,
type despite both of them being or by entire defective
different dominant alleles. chromosomes. These disorders
caused by defective chromosomes
Polygenic traits are called chromosomal
disorders. Downs Syndrome is an
Polygenic traits are traits
example of a chromosomal
controlled by multiple genes. For
disorder.
example, human height and skin
color traits are controlled by Using simple Punnett Squares, and
multiple genes. Mendel’s laws, we can figure out
how genetic disorders are
inherited.
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