Download Biology 2: Concepts in Genetics - CarrollGenetics

Genetics
Spring 2013
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. segregation vs. independent assortment
4. Contrast each of the following pairs of concepts:
a. variable expression vs. complete penetrance
b. maternal inheritance vs. mitochondrial 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
Total
Expected
Number (e)
d
(o – e)
d2
d2 / e
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:
Phenotypes
Red-eye
female
White-eye
female
Red-eye male
White-eye
male
Total
Observed
Number (o)
60
60 red-eye females
40 white-eyed females
45 red-eyed males
55 white-eyed males
Expected
Number (e)
d
(o – e)
d2
d2 / e
40
45
55
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. 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 courtordered 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.