A. Incomplete Penetrance
B. Variable Expressivity
C. Lethal Alleles
D. Pleiotropy
E. Phenocopy
F. Genetic Heterogeneity
1. Gene X causes skin rashes, weak bones, a sunken in chest, and hair loss.
2. Gene X, Gene R, Gene T will all cause a person to be colorblind.
3. When someone inherits the genotype of Mm, they should have very tight skin, but
sometimes an individual will exhibit the recessive phenotype where their skin
seems like it is falling off of their body.
4. Dorothy, an achondroplasiac dwarf, passed on a dominant A to her offspring as
did her husband, Theodore. Dorothy did not realize that she conceived a child
because it was spontaneously aborted in the womb.
5. Gene E causes a disease of the skin. Some people will have a small rash on their
thighs, but others may have the rash that covers over 80% of their body.
6. A person who has been complaining of inflammation in their knuckles is blaming
arthritis on his parents. He neglected to remember that he has been cracking his
knuckles for his entire life.
7. The protein, catalase, is used as an enzyme in numerous chemical reactions.
Unfortunately, Samatha does not have the ability to break down catalase, so she
has been suffering from constant stomach problems, kidney problems, as well as a
central nervous problem.
8. Male pattern baldness can affect men differently. Some will start balding in the
back, while others will start to bald in the front. Others will begin to see a
thinning all over their head.
9. Neurofibromatosis is a disease caused by mutations in the neurofibromin gene
(OMIM, 2008b). These mutations can cause the Schwann cells in an affected
individual's nervous system to grow into tumors called neurofibromas, which
appear as café-au-lait colored spots or bumps under the skin. These tumors can
result in skeletal abnormalities and neurological problems. However, not all
people who have the mutated neurofibromin gene are equally affected by this
condition. Research has shown that family members who carry the same mutated
gene can exhibit a range of symptoms, with some individuals experiencing much
more severe symptoms than others, although they all carry the same allele
10. Shaded individuals are affected by a dominant disorder.