Worksheet BIO102 Genetics
1. The w (white eye) gene is located on the X chromosome in Drosophila. w+ represents the
wildtype allele. w is the mutant allele. A white-eyed female is mated with a red-eyed
(wildtype) male. What phenotypes and genotypes are expected in the offspring?
Answer: All red females all white males
2. Hemophilia is an X-linked blood clotting disorder, most commonly observed in males. A
normal man has a child with a heterozygous (carrier) woman. What is chance of a hemophiliac
son? Daughter? Answer: 50% of sons and 0% daughters
3. Fill in the number
a.
b.
c.
d.
e.
f.
g.
h.
i.
_____ sex chromosomes in a human cell
_____ Barr bodies in a female cell
_____ possible genotypes for males with colorblindness
_____ number of types of gametes produced by individual with genotype AaBb
_____ number of months gestation that a human embryo begins to develop gonads
_____ number of chromosomes in a somatic cell of a person with Down syndrome
_____ number of X chromosomes in a cell from an individual with Turner syndrome
_____ number of SRY alleles in a human male cell
_____ number of Barr bodies in a cell of a person with genotype XXY
Answer: 2, 1, 1, 4, 2, 47, 1, 1, 1
4. A fruit fly has vestigial wings, a recessive mutation.
a. Using fruit fly notation, represent the normal and abnormal allele
b. What is the term used to represent the normal phenotype in fruit flies?
Answer: normal allele = v+ abnormal allele = v
wildtype
5. Using a Punnett square, show why 50% of offspring are expected to be male and 50% female
Answer
X
X
X
XX
XX
Y
XY
XY
6. Fill in with the appropriate term:
a.
b.
c.
d.
A small piece of a chromosome breaks off and is lost ________________
A small piece of a chromosome breaks off and attaches to another chromosome _____
A chromosome that is not a sex chromosome _________________
The alleles of different genes are on the same chromosome and thus do not assort
independently during meiosis ________________
e. The syndrome associated with genotype 47, XY, 21+ ______________________
Answer: deletion, translocation, autosome, linked, trisomy 12 (Down)