Download Problem Set 2B

Problem Set 2B
9-26-06
Name and Lab Section:_____________________
NOTE: You’re receiving this file as a Word document so that you can format it
differently if you want to in order to have the amount of space you want for answering
the questions. Please leave the questions in this order though.
1. Define each of the following rearrangements (mutations) (use one phrase or sentence for
each). Then describe what kind of chromosomal structure you might see in cells in meiotic
prophase I if those cells are heterozygous for each of these rearrangements (one phrase or one
sentence). If possible, give enough detail to distinguish each rearrangement from the others in
your description of what you might see.
A. deletion
B. duplication
C. inversion
D. translocation
2. Draw a pair of homologous chromosomes as they would be matched during prophase I if
they had a paracentric inversion. (be sure to give yourself plenty of space so drawing is clear)
Let the original gene order on these chromosomes be: L, M, N, centromere, O, P, Q, R, S, T.
Let one of the chromosomes contain an inversion that includes P, Q, and R. Remember that
the chromosomes are duplicated at this time, and thus contain sister chromatids. (For the exam
you should be able to do this for deletions and duplications too.)
3. Now assume that a crossover occurs between genes Q and R. Draw 4 possible
chromosomes (with letters included) that might arise from this by the end of meiosis II (there
might be one of each of these chromosomes in 4 different gametes).
4. Compare legitimate recombination to illegitimate recombination. Which is more common?
5. Most cases of autosomal aneuploidy in humans involve the small chromosomes. Why is
this?
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6. Red-green color blindness is an X-linked recessive disorder. Bob has a 47,XXY karyotype
(Klinefelter syndrome) and is color blind. His 46,XY brother, Tom, is also color blind. Both of
their parents have normal color vision. Where did the nondisjunction occur that caused Bob to
be color blind and have Klinefelter syndrome?
7. Why does recombination in the inversion regions appear to be suppressed in individuals
heterozygous for paracentric and pericentric inversions?
8. Give two ways that translocations can produce phenotypic effects.
9. Draw a temperature profile graph for 2 cycles of PCR, giving an approximate temperature
at each stage, and tell in one short phrase what happens at each of those stages. You could
write each of the phrases alongside each step in the profile.
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10. Use an entire sheet of paper for this drawing to give you plenty of room. It doesn’t need to
be neat, only clear.
Draw three base pairs of a DNA molecule that has the sequence 5’-GCA-3.’ Draw one
strand down the page on the left, and the other strand base-paired with it just to the right. Use
the same amount of detail as we used in class. Show the negative charge on each phosphate
group, label the 5’ and 3’ carbon positions with numbers, and show the hydrogen bonding
between paired bases with dashed lines (even though they don’t need to be placed accurately
with respect to specific atoms). Label the 5’ and 3’ ends of each strand. The only nitrogen
atoms you need to show are the ones in the bases that form the covalent bonds with the
deoxyriboses.
Place a small star next to each carbon atom that would have a hydroxyl (-OH) if the left
strand were an RNA molecule.
11. In the 1920’s Griffith did an experiment with bacteria and mice that showed there exists a
“transforming” material that can change the genetic characteristics of an organism. What was the
characteristic that was passed from one bacterium to another?
What did he do to ensure that the bacteria which originally had the characteristic weren’t
merely passed through the critical experiment?
12. What is euchromatin? (one phrase or sentence) What is heterochromatin? (one phrase or
sentence) In which type of material does most transcription occur?
13. What is a nucleosome and what are two of its functions? Name the 8 proteins classically
considered to be an essential part of the nucleosome core.
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14. In this problem you will do four very simple drawings (a-d).
a. Draw a DNA molecule as it would look before it is denatured, preparatory for PCR
amplification, using only lines with arrows at the ends to show the 5’ and 3’ ends. Here is that
molecule to get you started. Ignore the letters A and B for the moment.
A
B
b. Now draw that DNA as it would look during the heat denaturation step in the first
cycle of a PCR.
c. Now draw that DNA as it might look during the annealing (or hybridization) step
just after two PCR primers have annealed to it. Let the primers anneal at positions A and B
and draw them as short arrows oriented with their 3’ ends pointing in the direction of the
arrow.
d. Now draw those DNA molecules as they would look after the first extension step in
which Taq polymerase had extended from the primers. Let any newly synthesized DNA be
shown as a wavy line with an arrow at one end to signify the 3’ end. Cool! You’ve got more
DNA than you started out with!
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