Download Advanced Genetics Problems PURPOSE: To predict and compare

Advanced Genetics Problems
PURPOSE: To predict and compare the genetic variations that will result from a genetic cross.
Codominance occurs when both alleles contribute to the phenotype, leaving a phenotype that is
intermediate of the parents.
Example: Red flowers are fertilized by white flowers. The resulting offspring have pink flowers.
PRACTICE:
1. Sickle cell anemia is a codominant disorder, where N stands
for normal red blood cells and n stands for sickle-shaped red
blood cells. Heterozygous individuals have a phenotype
showing both sickle-celled and normal-shaped red blood cells.
Cross two people who are heterozygous for this trait.
**Remember to express probability in percentage form.
a. What is the probability their offspring are likely to have sickle cell anemia? ______________________
b. What is the probability their offspring will have both normal and sickle cell-shaped red blood cells? ___
c. What is the probability their offspring will be able to pass along the sickle trait to their children? _____
2. Multiple alleles occur when a trait has more than just a dominant and recessive allele. For example,
coat color in rabbits is determined by a single gene with four different alleles: C, cch, ch, c . The
combination of two of these alleles determines the rabbit’s phenotype.
Full color (C) - brown
(dominant to all other alleles)
CC, Ccch, Ccch, Cc
Chinchilla (cch) – gray
(dominant to ch and c)
cchch, cchcch, cchc
Himalayan (ch) – mostly white
(dominant to c allele)
chch, chc
Albino (c) – no color
(recessive to all other alleles)
cc
a. If a homozygous Himalayan rabbit and an albino rabbit mate, what are the possible phenotypes of their
offspring? ________________________________________________________________________
3. Blood types are controlled by multiple alleles. Look at the chart below containing blood types for the
human population. Type A and B are both dominant, while type O is recessive.
BLOOD TYPE
A
B
AB
O
GENOTYPES
IAIA, IAi
IBIB, IBi
IAIB
ii
a. A man with type O blood marries a woman with type AB blood.
What is the probability that they will have a child with type A
blood? _____________________________________________
(Show your work in a Punnett Square.)
b. If a child has type A blood and the father has type AB blood, what are the child’s possible genotypes?
_________________________________________________________________________________
c. If a child has type AB blood and the mother has type B blood, what blood type does the father have?
_________________________________________________________________________________
d. Vincent has type A blood and his mother has type O blood. What is his genotype? _______________
e. Christy has type B blood and her father has type O blood. What is her genotype? ________________
f.
If Vincent from problem 3 and Christy from problem 4 have
children, what are the children’s likely genotypes?
___________________________________________________
(Show your work in a Punnett Square.)
4. Sex-linked genes are so-called because they are located on one of the sex chromosomes, either the X
or the Y. Since the X chromosome contains more genes than the smaller Y chromosome, mutations on
the X appear more frequently in the population. In addition, sex-linked disorders are found more
commonly in males than females because they have only one copy of the X chromosome. The
genotypes for sex-linked traits are also written with superscripts: XBY or XbY for males or XBXB, XBXb, or
XbXb for females.
Complete the following chart by giving the phenotypes and genders for the following genotypes, X N gene
for normal vision and Xn gene for color blindness.
GENOTYPE
PHENOTYPE
XNXN
XNY
XNXn
XnY
XnXn
a. What are the possible genotypes and phenotypes resulting from
a cross between a carrier female for color blindness and a
normal vision male? __________________________________
___________________________________________________
(Show your work in a Punnett Square.)
GENDER
b. Duchenne Muscular Dystrophy is caused by a recessive allele
located on the X chromosome. Affected people experience
progressive weakening and loss of skeletal muscle. How can two
unaffected people can have a child with Duchenne MD?
___________________________________________________
(Show your work in a Punnett Square.)
a) Is the child with MD a male or female? _______________________________________________
b) Who did this child inherit the disorder from? Why? ______________________________________
c)
What is the probability that the couple’s next child will have MD? __________________________
d) What percentage of the couple’s female children will probably have MD? ____________________
e) What percentage of the couple’s male children will probably have MD? _____________________
d. Hemophilia is caused by a recessive allele on the X chromosome
that causes abnormal clotting of blood when cut or bruised. How
can a mother whose blood clots normally can have a daughter
with hemophilia.? ____________________________________
___________________________________________________
(Show your work in a Punnett Square.)
a) What is the father’s genotype? _____________________________________________________
b) Why is it extremely rare for a female to have hemophilia? ________________________________
c) What is the probability that their offspring will have hemophilia? ___________________________
d) What is the probability that their offspring can pass hemophilia on to their children? ____________
e) In this case, what do we call the mother if she is heterozygous for this trait? __________________
e. Not all sex-linked genes are recessive. For example,
hypophosphatemia, which causes defective bone development is
caused by a dominant allele on the X chromosome. Work a cross
showing a woman with a genotype of XAXa and a man with a
genotype of XaY.
a) What are the phenotypes of the mother and father? __________
___________________________________________________
b) What is the probability that the children will have hypophosphotemia? ______________________