Biology 101 – Quiz 13 – Exercise 14 – Useful Applications of Genetics
Name
1.
TRUE or FALSE:
(2 points)
Alleles NEVER control physiological traits, such as
production of digestive enzymes, hormones, and antibodies.
2.
Suppose that a male who is heterozygous (Tt) for the ability to taste PTC has 4 children with
a woman who is also heterozygous (Tt) for the ability to taste PTC. Will at least one of their
children DEFINITELY be UNABLE to taste PTC, i.e., will at least one of their children
DEFINITELY be homozygous recessive (tt) for the ability to taste PTC? Why/Why not?
(4 points)
NO! While it is statistically likely that one of the 4 will be able to taste the PTC, it is NOT a guarantee
3.
The following pedigree attempts to depict the transmission of cystic fibrosis, a disease caused
by a non-sex-linked recessive allele.
Unfortunately, this diagram is incorrect. Fix it by coloring in the appropriate square(s) or
circle(s). (6 points)
The easiest way is to just shade in a single circle.
4.
Billy Bob is NOT a hemophiliac (hemophilia is a X-linked recessive disorder). Billy Bob has a
daughter, Edna, with Noreen, a carrier of the hemophilia trait. What are the chances that
Edna will be a hemophiliac? What are the chances that Edna will be a carrier of the
hemophilia trait? (5 points)
Since Billy Bob is not a hemophiliac, Edna will receive an X chromosome with the dominant
healthy allele from him. Thus there is no chance of her being a hemophiliac.
However, she has a 50% chance of being a carrier since she has a 50% chance of receiving
the X chromosome with the recessive allele from her mom.
5.
Deleterious (disease-causing) alleles are often gradually reduced in frequency as those
individuals who have the disease are less likely to reproduce. What is one reason for the
continued prevalence of the sickle-cell trait among people who reside in central Africa? (4
points)
Sickle-cell trait prevents the contraction of malaria
6.
Suppose you crossed a yellow flower (YY) with a blue flower (yy). You discover that the
offspring are all GREEN! What is the genotype of the offspring? What type of inheritance
is this an example of? (5 points)
Genotype is Yy. It’s an example of incomplete dominance.
7.
Albinism is a recessive disease where the afflicted individual cannot synthesize melanin. If
you crossed someone who is homozygous dominant for the normal melanin allele with
someone who is a carrier of the albinism trait (but who is not an albino), what are the
chances that any of their children could be albinos? ( 6 points)
There is no chance that any of the children could be albinos because one of the parents has no
recessive allele to pass on.