Download Exam 2 Student Key

Biol 200, Spring 2014
Exam 2,
*****KEY*****
This exam is worth 100 points. There are four pages of questions.
(Note – there are two versions….)
1. (10 pts) For each of the following molecules or structures, write the letter for the category of
biological macromolecule it is or is made of. IF IT CONSISTS OF TWO TYPES, write both letters.
1 pt each
Category:
a. N cAMP
f. N, P spliceosome
C = carbohydrate
b. P CAP
g. N enhancer
L = lipid
c. P kinetochore
h. N, P chromatin
N = nucleotide or nucleic acid
d. N(P) centromere i. C lactose
P = protein or amino acid
e. P microtubule j. N (P) telomere
For centromere and telomere we accepted P if you also
answered N, since DNA is always associated with histone proteins.
2. (12 pts) For each description, write TWO different answers. (There may be more than 2 answers.
Please write ONLY TWO! You can use the same answer for different descriptions.)
2 pts each
a. Protein that can interact with DNA in a
helicase, DNA pol I,III, ligase, RNA pol…
non-specific manner (bind any sequence).
b. Enzyme that can break phosphodiester bonds DNA pol I, III, topoisomerase
c. Specific gene or protein whose expression
is constitutive. (Give us names!)
LacI, RNA pol, CAP, rRNA genes, tRNA genes,
glycolytic enzymes, etc….
3. (8 pts)
We took off one point for each missing or incorrect answer, bottoming out at zero.
Description
DNA
Homologous
Sister
replicates chromosomes pair chromatids
up and recombine
separate
a. Follicle cells that are dividing in a
X
X
maturing follicle in the ovary
b. 1° Oocyte
X
X
X
X
c. Differentiated neuron that is in G0
d. Spermatogonium
Histones
are
present
X
X
X
X
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Biol 200, Spring 2014
Exam 2,
*****KEY*****
4. (10 pts)
a. (4 pts) Draw in the two new DNA strands that will be found when replication is COMPLETE,
assuming that the RNA primers are 3 nucleotides long in this organism.
a
c
5’
C G C C T A A T T G G A C T A C G
G C G G A T T A A C C T G A
3’
5’
5’
C T A A T T G G A C T A C G
G C G G A T T A A C C T G A T G C
3’
3’
b
3’
5’
d
b. (2pts) If telomerase is active in this cell, to which end(s) (a-d) will
it add nucleotides (covalently)? (Write ALL correct answers) b and c
c. (2pts) Which of the following could be the template molecule
that telomerase carries and uses for DNA synthesis? (Write the ONE best answer) 2
1:
5’ CGGCCTAT 3’
3’ GCCGGATA 5’
2:
3’ GCCGGAUA 5’
3:
5’ CGGCCUAU 3’
3’ GCCGGAUA 5’
4:
3’ GCCGGATA 5’
d. (2pts) In which of the cells below would you likely find active telomerase? (Circle ALL correct)
- spermatogonia
- differentiated muscle cells
- cancer cells
5. (6 pts) Imagine there are twin sisters, Abby and Babs. They both inherited mutations in their DNA
Polymerase III genes that make the enzyme slightly less efficient at proofreading. Abby gets three
different cancers before age 60. Babs never gets cancer. Assume both sisters are accumulating
mutations in their DNA at the same rate.
a. (4 pts) Explain how mutations cause Abby's cancers. (No more than 2 sentences)
Random mutations must be occurring to make either proto-oncogenes overactive or tumor
suppressors less active. This will increase the likelihood of cell cycle progression when it isn't
supposed to occur, therefore causing cancer.
b. (2 pts) Why doesn't Babs get cancer? (No more than 2 sentences)
Babs is lucky – the mutations she is accumulating are not strengthening protooncogenes or
weakening tumor suppressors.
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Biol 200, Spring 2014
Exam 2,
*****KEY*****
6. (12 pts) In the lab, you have three different plasmids, each containing a different version of the LacI
gene (that codes for the Lac Repressor protein).
Types of mutations:
a. (2pts) Match the repressor structure with the most likely
1. frame shift early in coding
LacI gene mutation. Each type of mutation will be used once.
sequence
2 Repressor protein A: has normal protein sequence
2. silent mutation in 4th codon
3 Repressor protein B: cannot bind lactose, but it
3. Single amino acid change
can bind the operator
(missense)
1 Repressor protein C: binds neither lactose nor DNA
b.(10pts) You insert the mutant LacI genes from above into normal E. coli bacteria that already have
their own wild-type LacI gene and wild-type Lac Operon on their chromosomes. Predict the amount
of β-galactosidase enzyme production in each cell by writing a "-" for low or no production, and a
"+" for high production.
Cell type
Lactose
alone
Glucose
alone
a. Normal E. coli with no plasmid added
+
-
b. Normal E. coli with Repressor A added
+
-
c. Normal E. coli with Repressor B added
-
-
d. Normal E. coli with Repressor C added
+
-
e. E. coli cell which ONLY has Repressors
B and C
-
-
7. (12 pts) Write the letter for the ONE BEST choice that describes what happens in a eukaryotic cell
with each mutation below, using the letters in the box. Not all choices will necessarily be used.
2 pts each
Choices:
B HAT (histone acetyltransferase) enzyme is less active
A. Increase in gene expression
C Intron splice site is deleted at the beginning of an intron
B. Decrease in gene expression
B Enhancer element deleted that is 1000 base pairs upstream
of (before) the promoter
C. Protein sequence change
D. No changes
C Deletion of 4 base pairs within exon 3 of a gene with
5 exons
D Deletion of 4 base pairs in the middle of intron 3 in a gene with 5 introns
A Regulatory transcription factor that activates formation of the transcription complex now has a
stronger binding site for mediator proteins.
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Biol 200, Spring 2014
Exam 2,
*****KEY*****
8. (10 pts) The image to the right shows the karyotype of a typical diploid
animal with 2N=6 chromosome number.
a. (4 pts) Draw the spindle and chromosomes in this cell
during metaphase of Meiosis II in this organism's
gonads. Make sure to draw the chromosomes carefully so
we can determine their type.
b. (2pts) In a male mammal, what is the name of the cell that
goes through this division?
2° spermatocyte
c. (2pts) Where would you find this cell in the gonad?
Towards the lumen of a seminiferous tubule
d. (2pts) Name one difference between the products of Meiosis in a male compared to a female
mammal.
Male makes 4 sperm, females 1 oocyte; sperm are small, oocytes large
9. (8 pts) Consider each pair of events in the zygote that occur after fertilization. Write an "X" in the
blank for the event that occurs FIRST in each pair. (2 pts each)
a. _____X____ Meiosis II is completed vs. DNA synthesis begins _________
b. _________ Genes are transcribed vs. protein activity increases ____X_____
c. _________ RNA synthesis begins vs. DNA synthesis begins ____X_____
d. _________ chromosomes condense vs. DNA synthesis begins ____X_____
10. (12 pts) You have several mutant sea urchins. You mix oocytes and sperm from a single female
and single male for each trial below. For each phenotype, name one PROTEIN that if non-functional,
would produce that phenotype. Then name whether that protein is mutant in the male or the female.
For some phenotypes, there may be more than one correct answer. Please name only ONE.
Fertilization phenotype
a. Polyspermy very common
Protein that is non-functional
(2 pts)
Cortical granule enzyme,
Sodium channel
Male or
Female? (1 pt)
Resact (Resact receptor)
Female (male)
Fertilizin (bindin)
Female (male)
Jelly coat (JC receptor)
Female (male)
b. Sperm cannot find oocyte
c. Sperm reach oocyte's plasma
membrane, but don't fertilize the oocyte
d. Sperm get close to the oocyte, but the
acrosome does not fuse with the sperm
membranes.
4
Female
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