University Biology: Risk Assessment Problem Set 1 - Genetics

This assignment provides solutions to a risk assessment problem set focusing on genetic disorders. The problems cover various scenarios, including the risk of offspring inheriting xeroderma pigmentosum (XP) and Bloom syndrome, both autosomal recessive conditions. The solutions detail the probabilities of offspring inheriting these conditions, along with the scenarios involving Tay-Sachs disease, Duchenne muscular dystrophy (DMD), Huntington disease, and X-linked disorders. The assignment explains the inheritance patterns, carrier status, and the implications of consanguinity. It also discusses the incidence of X-linked disorders in males versus females and provides insights into prenatal testing and family history in assessing genetic risks. Overall, the solutions offer a comprehensive understanding of genetic risk assessment in different scenarios.

Risk Assessment Problem Set
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A. Xeroderma pigmentosum also referred to as XP, is a disorder that
causes extreme sensitivity to Ultraviolet exposure. It is an inherited
condition and is represented by a recessive autosome. As a result, the
child of seemingly health parents can also have the disease. The
parents act as the carrier of the recessive gene. Since the woman’s
brother is diagnosed with XP means that her parents were also the
carriers of the gene.
B. Bloom syndrome is an inherited disease caused by a rare autosomal
recessive gene. People with Bloom syndrome have a short stature,
genomic instability and a higher chance of acquiring cancer. Even
though the parents of the child are healthy, they can have a single
recessive abnormal gene which is masked by the normal dominant
gene.
In case the woman has a child with her partner, there is a 25% chance
that the child will have normal genes, a 50% chance that the child will
have one normal and one diseases gene and 25% chance the child will
have two recessive genes and hence carry the disease.
C. There are chances though minimal in which the child has neither of
the two diseases.
D. XP gene is present on 19th chromosome and Bloom syndrome gene
on the 15th chromosome. Therefore, it is possible that the child has
both the disorder.
E. All the specified conditions are possible
2. The woman is likely to carry one recessive and one dominant gene
of the disease. Since the woman and her husband share a common
ancestor in the third generation and autosomal disorders often skip
generations, the next child can also be affected by the disease.
3. The Duchenne muscular dystrophy gene is present on the X
chromosome and only affects the males whereas the females act as
the carriers. In this case, the father has no abnormal gene but the
mother is a carrier as a result of which the son is affected. The
daughter is a carrier and hence the chances of the unborn baby having
the disease are 25%. There are several prenatal tests for diagnosing
whether the child has DMD or not. It is especially recommended for
people who have a family history.
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4. If 1:500 females are affected in case of an X chromosome-linked
disorder then chances of males having the disorder will be manifolds
higher.
5. Huntington disease is brain disorder which declines steadily and
causes uncontrolled movements, emotional imbalance and loss of
cognitive skills. Since Huntington disease is a inherited defect present
in a single dominant gene, this means that Betty is not a carrier or
affected by the disease. However, the chance of Betty’s son
developing the disease or not depends on whether her husband is
affected or not.
6. DMD is caused due to an abnormal recessive gene carried in the X
chromosome. It is possible that the females in Carol’s family have a
recessive X chromosome without it being represented or Carol’s son is
not the biologically related to them.
7. III:3 can be a carrier of the disease since her mother has one faulty gene
and there is 25% chance that she also has a faulty gene.
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