Genetics
Spring 2014
Examples of Questions for the First Exam
Answers to study questions will not be provided by the instructor during Question and Answers discussions
before the exam. During the “Q and A” class meeting, you’ll be able to discuss them with your classmates,
with the instructor acting as a moderator of the discussion. There should be no complaints about this
arrangement! (The reasonable alternative is that you see none of the questions before the exam.)
I encourage you to discuss these amongst yourselves, use your textbook, notes and class handouts (see the
course website). Please do not ask the instructor to recite the answers. The goal here is learning and critical
thinking, not whether you can recite what the teacher says. You may ask the instructor to clarify a question if it
is unclear, or for guidance in understanding concepts you need to answer certain questions. Be certain that you
understand this: the point here is not that you shouldn't ask for help, but instead that you bear the badge of
effort. If you're lost, ask for help.
Be advised that you are expected to have completely read the syllabus by now, including information about the
exams. One question on the exam will be based on your general understanding of the course syllabus.
Advice
You are obligated to cover completed answers. If you are observed not covering completed answers, you
may receive a score of zero for the exam.
Be concise in answering the questions: about 1/3 to 1/2 a page is enough for any of them. Note well: being
concise does not mean giving a minimal answer. You should give sufficient detail, and use appropriate
terminology correctly.
For short-answer questions, show your work or support your conclusions. In other words, you should
demonstrate that you understand how you reached your answer.
The exam is intended to be an approximate 90 minute exam, for students who are adequately prepared.
However, you should be careful to pace yourself during the exam. In most cases you are better off answering
all questions, even if some of them incompletely or incorrectly. Leaving short answer questions blank because
you ran out of time is usually worse for your exam score.
What’s important? See the lecture notes, lab handouts, and assigned readings for important concepts. If we
spent time with a concept in class or it appears in handouts, it’s fair game for the exam.
For questions that involve use of symbols, provide a key for any symbols that are not defined in the
question itself. For example, if you use the symbols C and c to represent alleles of a gene, you should provide
a description of the traits determined by each allele. (Note that the instructor is not a mind reader.)
Figures or tables may be appropriate for some questions. Figures must be large and neatly labeled. Tables
must have labeled columns and rows.
Be prepared to use terminology, and use it correctly. For example, you must understand the meaning of the
term double heterozygote to explain Mendel’s experiments demonstrating Independent Assortment. It’s too
easy to veer off course when you don’t know the correct term for a concept and instead try to explain it in
common language.
Questions:
These are examples of questions that represent the types of questions that could appear on the exam. It is not a
comprehensive guide to what might appear on the exam. See the lecture notes, lab handouts, and assigned
readings for other important concepts.
1. Contrast each of the following pairs of concepts:
a. gene vs. allele
b. haploid vs. diploid
2. Contrast each of the following pairs of concepts:
a. homologous chromosome vs. sister chromatid
b. heterozygote vs. heterogametic
3. Contrast each of the following pairs of concepts:
a. metaphase I of meiosis vs. metaphase II of meiosis
b. mitosis vs meiosis
4. Contrast each of the following pairs of concepts:
a. variable expression vs. incomplete penetrance
b. maternal effect vs. cytoplasmic inheritance
5. Which phase of Meiosis --- Meiosis I or Meiosis II --- is more similar to Mitosis? Explain.
6. Normal somatic cells of horses have 64 chromosomes (2n = 64). How many chromosomes and DNA
molecules will be present in the following types of horse cells?
Cell Type
a. Spermatogonium (G1)
b. First polar body
c. Primary oocyte
d. Secondary spermatocyte
# of chromosomes
_____
_____
_____
_____
# of DNA molecules
_____
_____
_____
_____
7. For a particular genetic strain of corn, you suspect that abnormal meiosis I in corn can result in color
variation in corn kernels that does not fit Mendel’s Principle of Segregation. In previously published
work, it was shown that in other strains of corn, there is an equal time span for each phase of Meiosis I.
You’ve collected the observed data below:
Mitotic Phase
Prophase I
Observed
Number (o)
30
Metaphase I
20
Anaphase I
35
Telophase I
25
Expected
Number (e)
d
(o – e)
d2
d2 / e
Total
2 = ________
Degrees of freedom (df) = ______
______ > P > ______
a. Complete the 2 table.
(For the exam, you would be provided with a copy of the 2 probability table.)
b. Write the null hypothesis (H0).
c. Briefly interpret of the results of the 2 test.
8. A woman has color-blindness, a sex-linked recessive trait. Her husband has normal vision. Their
daughter and son both have red-green color blindness. The man figures he cannot be the father of both
children and files for divorce. What is the probability that the couple could have borne the daughter?
The son? Show your work.
9. Interestingly, some flies have white eyes and others red eyes. The difference in eye color is due to
inheritance of one gene. Two true-breeding flies are mated, with the female white-eyed and the male
red-eyed. The F1 are ½ red eyed and female, and ½ white-eyed and male. (There are no white-eyed
females, or red-eyed males.)
The F2 includes:
60 red-eye females
40 white-eyed females
45 red-eyed males
55 white-eyed males
Phenotypes
Red-eye
female
White-eye
female
Red-eye
male
White-eye
male
Total
2 = ________
Observed
Number
(o)
60
Expected
Number
(e)
d
(o – e)
d2
d2 / e
40
45
55
Degrees of freedom (df) = ______
______ > P > ______
a. Complete the 2 table.
(For the exam, you would be provided with a copy of the 2 probability table.)
b. Write the null hypothesis (H0).
c. Briefly interpret of the results of the 2 test. In your answer, be certain that you identify the mode of
inheritance for the white eye color of flies.
10. Bob has XXY chromosomes (Klinefelter syndrome) and is color blind. His mother and father have
normal color vision, but his maternal grandfather is color blind. Assume that Bob’s chromosome
abnormality arose from nondisjunction in meiosis. In which parent and in which meiotic division did
nondisjunction take place? Explain your answer.
11. In chickens, congenital baldness is due to a Z-linked recessive gene. A bald rooster is
mated with a normal hen. The F1 from this cross are interbred to produce the F2. Give the phenotypes
and genotypes, along with their expected proportions, among the F1 and F2 progeny.
12. Lizzy and Marisa both had baby girls on the same days at the hospital. Lizzy named her girl Rowan,
and Marisa named her girl Samantha. When the mothers took their babies home, they began to wonder
if they had been accidentally switched, so that each mother had the wrong baby. Blood tests revealed
that Lizzy’s ABO blood phenotype is AB, her husband’s A, and the baby they took home B. Blood tests
revealed that Marisa’s ABO blood phenotype is B, her husband’s A, and the baby they took home O.
Had the babies been switched? Show your work.
13. Juan’s ex-wife gave birth to a daughter before they divorced, and has been paying court-ordered child
support payments as a result of the divorce proceedings. Now he is suspicious that he is not the father of
his supposed daughter. Juan does not know his ABO blood phenotype, but he knows that his parents are
types B and O. He also knows his ex-wife is type AB, and the daughter in question type AB. Is Juan
ruled out as the father of the child? Explain.
14. A genetic disorder caused by a recessive allele is characterized by falling asleep in genetics lectures
when the lectures begin at 8 a.m. It is also characterized by waking up as the lecture ends. The disease
is known to be 20% penetrant, and complete expressivity occurs in only 80% of people that exhibit the
disorder. (You may assume that all affected individuals must be homozygous recessive for the gene.)
a. Must the percentages of penetrance and expressivity sum to 100% ? Explain.
b. What percentage of students who are homozygous for the disorder will both fall asleep at 8:00
a.m. and still be sleeping after the lecture ends? Show your work.
15. Answer question 5.16 on page 129 of your textbook.
16. Answer question 5.22 on page 130 of your textbook.
17. Joanna has “short fingers” (brachydactyly). She has two older brothers that are identical twins; both
have short fingers. Joanna’s two younger sisters have normal fingers. Joanna’s mother has normal
fingers, and her father has short fingers. Joanna’s paternal grandmother (her father’s mother) has short
fingers; her paternal grandfather (her father’s father), who is now deceased, had normal fingers. Both of
Joanna’s maternal grandparents (her mother’s parents) have normal fingers. Joanna marries Tom, who
has normal fingers; they adopt a son named Bill who has normal fingers. Bill’s biological parents both
have normal fingers. After adopting Bill, Joanna and Tom produce two children; an older daughter with
short fingers and a younger son with normal fingers.
a. Using standard symbols and labels, draw a pedigree illustrating the described family.
b. What is the most likely mode of inheritance for short fingers in this family?
c. If Joanna and Tom have another biological child, what is the probability (based on your answer
in part b) that this child will have short fingers?
18. Explain how concordance studies in twin pairs are used to determine if a trait has a genetic component,
and give an example.
19. See question 6.23 in textbook (page 158)