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Name_______________________
Bio 212 Genetics
Exam I Spring 2005
80 points
Please put your name on your exam and your scantron. Be sure to read all
questions carefully and show your work for complete credit. Please transfer your
answers to questions 1-20 to the scantron and darken the appropriate boxes with a #2
pencil. Questions 21 and 22 are problems that should be answered on the exam itself. A
table of Chi-square critical values is included on the bottom of page 7. If you use extra
pages as scrap paper, sign them and turn them in with your exam.
Part I. Multiple choice, 3 pts. each. Select the one best answer.
1.
a.
b.
c.
d.
The term genotype describes the
specific combination of alleles in a cell
outward appearance of some characteristic in an individual
fundamental unit of heredity
physical location of a gene on a chromosome
2. A cross of a true-breeding blue-flowered plant and a true-breeding white-flowered
plant gives all pale-blue-flowered plants. The F2 generation produced from intercrossing
the F1 plants gives:
27 blue
49 pale-blue
24 white
These results suggest that the pale-blue trait is due to
a. Incomplete dominance
b. Recessive epistasis
c. Variable expressivity
d. Simple dominance
3. Bar is an X-linked dominant trait in Drosophila that determines eye shape. Bar males
would have the genotype
a. XBY
b. XBXB
c. XbY
d. XBYB
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4. The following F2 results occur from a dihybrid cross of doubly heterozygous F1
individuals:
purple:
white:
white:
white:
A_B_
aaB_
A_bb
aabb
9/16
3/16
3/16
1/16
If a double heterozygote (AaBb) is crossed with a fully recessive organism (aabb) what
phenotypic ratio is expected in the offspring?
a. 3 purple: 1 white
b. 1 purple: 1 white
c. 9 purple: 7 white
d. 1 purple: 3 white
5. The following images are of meiocytes from a female and male Ascaris in the same
stage of cell division. If the diploid number of chromosomes is 4, which stage are the
cells in?
a.
b.
c.
d.
prophase I
metaphase I
anaphase II
metaphase II
6. Dentinogenesis imperfecta is a rare, autosomal, dominantly inherited disease of the
teeth which occurs about one in 8000. Assume that a male with dentinogenesis
imperfecta and no family history of the disease, marries a woman with normal teeth.
What is the probability that their first two children will have dentinogenesis imperfecta?
a. 1/4
b. 1/2
c. 3/4
d. 9/16
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7. The white-eye gene in Drosophila is recessive and sex-linked. Assume that a whiteeyed female is mated to a wild type male. What would be the phenotypes of the F1
offspring?
a. all wild-type (red) eyes
b. 50% white eye males, 50% red eye females
c. 50% white eye females, 50% red eye males
d. 50% white eye males, 25% red eye females, 25% white eye females
8. Which of the following is NOT true about homologous chromosomes?
a. homologous chromosomes are identical in length
b. homologous chromosomes share the same centromere locations
c. one of each pair of homologous chromosomes is produced from the other in S phase
d. homologous chromosomes carry the same sequence of gene sites (loci)
9. The following pedigree was obtained for a rare kidney disease. Assume that
individuals that marry into the families do not carry the trait. Most likely this disease is
inherited as
a.
b.
c.
d.
autosomal dominant
X-linked dominant
autosomal recessive
X-linked recessive
10. During meiosis __________.
a. the chromosome number is doubled
b. two identical cells are produced
c. the chromosome number stays the same
d. the chromosome number is reduced by half
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11. Normal parents have a Tay-Sachs child. Tay-Sachs is an autosomal recessive
condition. What is the probability that their next child will be normal?
a.100%
b. 25%
c. 75%
d. 0%
12. The stage of meiosis in which crossing over occurs, increasing variability in the
gametes is
a. prophase II
b. metaphase I
c. telophase II
d. prophase I
13. What genotype is present most often among the progeny (F2) of a dihybrid cross
(AaBb X AaBb)?
a. aabb
b. AAbb
c. AaBb
d. AABb
14. In a paternity suit a man disputes that he is the parent of a child although the mother
of the child says that he is. The man has type O blood. The child also has type O blood,
and her mother has type B blood. Could he be the father?
a. no, because type O is only found in homozygotes
b. no, because B is dominant to O
c. yes, because the mother could be heterozygous
d. yes, because the allele for type O is dominant
15. A female is heterozygous for the recessive X-linked gene for Lesch-Nyhan syndrome,
a recessive gene that leads to mental retardation, self mutilation, and early death. What
proportion of her daughters will be "carriers" for the trait? (Assume father is normal)
a. 0%
b. 25%
c. 50%
d. 75%
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16. In mice, the allele A causes agouti banding of hairs and is dominant to the allele a, so
that aa mice are solid black. The allele C causes color and is dominant to c and cc mice
are albinos. When a mouse is albino, its color cannot be shown. Heterozygous CcAa
mice are crossed to ccaa mice. What will be the phenotypic ratios in the progeny?
a. 2 agouti: 1 black: 1 albino
b. 1 agouti: 2 black: 1 albino
c. 1 agouti: 1 black: 2 albino
d. 1 agouti: 1 albino
17. Two traits studied by Mendel are round pea shape, which is dominant to wrinkled
and yellow color, which is dominant to green. In a cross of a heterozygous round yellow
pea plant (WwGg) with a plant that is homozygous dominant for the round trait and
homozygous recessive for the green trait, what is the proportion of offspring that are
round and green?
a. 1/4
b. 1/2
c. 3/16
d. 9/16
18. How many different types of gametes can be formed by an individual with the
genotype AaBbCc?
a. two
b. four
c. six
d. eight
19. Mendel's law that describes the separation of alleles during gamete formation is:
a. the law of independent assortment
b. the law of segregation
c. the law of dominance
d. the law of heterozygosity
20. (bonus question) A father with myotonic dystrophy has three daughters who are all
carriers of the mutant allele and two sons who are unaffected noncarriers. The three
daughters have six sons of which four are affected and two are not, and four daughters of
which two are carriers and two are not. What type of mutation is suggested from this
description?
a. autosomal dominant
b. autosomal recessive
c. sex-linked dominant
d. sex-linked recessive
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Part II. Problems: Show your work for full credit and answer on these pages or on
additional sheets.
21. (16 points) In silkworms, the hemolymph may be deep-yellow or white. Fully
formed larvae may be plain or moricaud (heavily lined). A cross is made between two
true-breeding strains, deep-yellow plain and white moricaud. When 10 F1 females are
crossed with 10 F1 males, the following progeny result:
Deep-yellow, moricaud
Deep-yellow, plain
White, moricaud
White, plain
293
96
104
38
a. How many genes are involved?
b. Define allele symbols for each gene and indicate which allele is dominant.
c. Give the genotypes of the P1 generation ____________________________.
d. Give the genotypes of the F1 progeny ______________________________.
e. Clearly state a hypothesis regarding the F2 phenotypic ratio.
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21. (cont.) f. Test your hypothesis using a Chi-square test
Phenotypes
Observed
Expected
ObservedExpected
(ObservedExpected)2
(ObservedExpected)2/Expected
χ2= _________________
Degrees of freedom = ________
χ2 critical value at probability = 0.05 is _______________________________________
Would you accept or reject your hypothesis? ___________________________________
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The following question deals with lethal genes, since I didn’t get a chance to do an
example, there will not be a question like this on Exam I Fall 2006:
22. (7 points) In crosses between two crested ducks approximately 3/4 of the eggs hatch.
The embryos of the remaining quarter develop nearly to hatching and then die. Of the
ducks that do hatch about 2/3 are crested and 1/3 are crestless.
a. Explain these results genetically.
b. What phenotypic ratios would you expect from the cross of a crested with a crestless
duck?
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