Human Biology

Genetics Worksheet and Problem Set Section_______________________________
General Questions 1-6: (1 point each)


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. Mendel concluded that when each set of homologous chromosomes separated, how another set of chromosomes separated had no effect. This premise became one of his laws of inheritance referred to as the __________________________________________________.
3. Alternative forms of a gene that occur at the same locus on homologous chromosomes are termed

4. Your _____________________________ is the physical and functional expression of the genes you inherited.

5. Chromosomes fit into two general categories. Those involved in the determination of sex are termed the “Sex Chromosomes”. Those chromosomes not involved in sex determination are termed

6. Why is it that siblings, who come from the same set of parents, do not necessarily look alike? Give at least one possible explanation based on what your knowledge of meiosis and genetics. That is, think about the process of meiosis and the events that occur. Choose one of the events in meiosis, which you feel would account for the differences one sees in siblings who are born to the same set of parents. Be specific and do not just reword the question. (1 pt.)


7. 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. (1/2pt)
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.) _____________________________________________________________2

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8. Phenylketonuria (PKU) is a disease found in humans in which the affected individual does not have the enzyme phenylalanine hydroxylase. This enzyme is needed to metabolize the amino acid phenylalanine to tyrosine. When left untreated the phenylalanine converts 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? (1/4pt.) _________________________________

B. Explain how you came to this conclusion? (1/4 pt.)_______________________________________


C. What are the genotypes of the each of the parents? (1/4 pt.)

D. What is the genotype of the child with PKU? (1/4 pt.)____________________________________

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. (1/2pt. for Punnett square)

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?
(1/4 pt.)_____________________________________
c. What is the probability that the first child will NOT have either disorder?
(1/4 pt.)_______________________________________________________3

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Genetics Bonus Questions:

Autosomal recessive polycystic kidney disease (ARPKD) is the lesser common of the two types of polycystic kidney disease, occurring in 1:20,000 live births, but it is also the most deadly. It is generally identified in the first few weeks after birth. Unfortunately, the kidneys are often underdeveloped resulting in a 30% death rate in newborns with the recessive version of the disease.

Suppose a man who is phenotypically normal, and whose mother was normal but his father had polycystic kidney disease, marries a woman who is also phenotypically normal. The parents of the woman are both normal. They are concerned that their children may inherit this disorder and decide to come to you, their genetic counselor.

You sit down to explain to them that there may be cause for concern depending on their actual genotypes. Using one or more Punnett squares show ALL possible scenarios to this couple using the information you know about each of them and their parents. For each scenario provide the percent possibility or chance for a child to have the disorder, if any. Show your work. (2 pts)

The Genetics of Health Aging and Longevity

Last Updated on July 17, 2020 by EssayPro