Download Genetics Constructed Response Answer

Name:________________________________________Date:___________________Period:___________
Genetics Constructed Response
Directions: Please read all parts of the example below and answer all four points for this constructed
response completely. Be sure to read carefully, and check your answers once done.
There is a genetic disorder that is sex-linked and is caused by a recessive allele (e). The allele for the
unaffected condition (E) is dominant. A woman who is a carrier of this disorder marries an
unaffected man. The couple would like to have a child, but they are concerned that their child will
inherit the disorder.
Using this example:
 Construct a Punnett square to illustrate the inheritance of this cross.
 Provide the genotypes of the woman and the man and the possible genotypes of their future
children
 Calculate the probability that they will pass the condition on to their offspring.
 Explain the pattern of inheritance of a sex-linked trait
The response should demonstrate understanding of Mendelian genetics and patterns of inheritance as they
relate to sex-linked disorders.
XE
Xe



XE
Y
XEXE
XEY
XEXe
XeY
Genotypes: Mother XEXe, father XEY and children XEXE, XEXe, XEY, XeY
Probability: 25% chance that the male child would inherit the disorder from his mother. 25%
chance that one female child would carry the recessive allele for the disorder. 50% chance that two
out of the four offspring will not inherit the recessive allele (e).
The patterns of inheritance for sex-linked traits are: typically found on the X chromosome; passed
from the mother to her male offspring. Females can express a sex-linked trait if the trait is
expressed in the father and the mother is a carrier. Sex-linked traits are normally recessive alleles
carried by the mother.