1. An allele which exerts its phenotypic effect in the heterozygote is referred to as being ___________________________. That is, it masks the expression of the other allele.
2. The separation of homologous chromosomes at the time of gamete formation is what is referred to as Mendel’s _____________________________
_____________________
3. Alternative forms of a gene that occur at the same locus on homologous chromosomes are called _____________________________
___.
4. Your _____________________________ is the physical and functional expression of the genes you inherited.
5. Chromosomes not involved with sex determination are referred to as __________________________.
6. Why is it that siblings, who come from the same set of parents, do not necessarily look alike? Give at least two possible explanations based on what your knowledge of meiosis and genetics.
Both Josh and Janet have a widow’s peak hairline. Their son Jeremy has a straight hairline, while their daughter Jennie has the widow’s peak.
A. Using a Punnett Square show how this is possible.
B. Josh and Janet were to have another child, what would be the probability that this child would have a
widow’s peak? (1/2 pt.) _____________________________
_____________________________
___
8. Phenylketonuria (PKU) is a disease found in humans in which the affected individual does not have the enzyme phenalalanine hydroxylase. This enzyme is needed to metabolize the amino acid phenalalanine to tyrosine. When left untreated the phenylalanine will be converted to phenylketone and accumulates in the body leading to brain development disorders, mental retardation and seizures. Suppose two normal adults have one child who has the trait and a second child who is normal.
A. Is PKU inherited as a dominant or recessive trait? _____________________________
____
B. Explain how you came to this conclusion? _____________________________
__________
_____________________________
_____________________________
_____________________________
_____________________________
_____________________________
_______________
C. What are the genotypes of the parents? _____________________________
_____________
D. What is the genotype of the child with PKU? _____________________________
_______
2
9. In humans, a dimple in the chin is a single gene, autosomal dominant characteristic. A man with a dimpled
chin, whose mother lacked the dimpled chin, marries a woman without a chin dimple. What proportion of
their children would be expected to have a chin dimple?
A)¼
B) ½
C) ¾
D) All of these are correct
E) None of these are correct
10. It is known that achondroplasia (dwarfism) and Huntington’s disease (a neuronal degenerative disease) are both inherited as dominant traits in humans.
Using A=achondroplasia and H=Huntington’s disease, answer the following questions and use a
Punnett square to show how you determined your answers.
b. What is the probability that the first child of parents who are heterozygous for both traits will display achondroplasia but not the Huntington’s disorder?
_____________________________
________
c. What is the probability that the first child will NOT have either disorder?
_____________________________
__________________________
Q:
Imagine that you are a genetic counselor, and a couple planning to start a family come to you for
information. Louis was married once before, and he and his first wife had a child with cystic fibrosis.
His current wife, Annabelle, had a brother who died of cystic fibrosis. The couple is concerned that they
might have a baby with cystic fibrosis even though neither of them have the disease themselves.
You know that cystic fibrosis is a lethal, recessively inherited disease.
A. What is the genotype of Louis? _______
B. Can you definitely determine Annabelle’s genotype? (yes or no) ___ _________
C. What might Annabelle’s genotype(s) be? __ ______________
D. What will you tell the couple with regards to their chances of having a child with cystic fibrosis?
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