Biology 115, Fifth Quiz: 18 April 2000
A. Multiple choice questions: 0.5 points each.
- 1. (d)
- 2. (c)
- 3. (c)
- 4. (b)
- 5. (d)
- 6. (a)
B. Definitions: 0.5 points each.
- 7. A polar body is a nonfunctioning daughter cell formed during
oogenesis. It has little cytoplasm.
(0.1 for the fact that it's a cell; 0.2 for the fact that it's nonfunctional,
0.2 for its formation during oogenesis.)
- 8. A codon is a triplet of bases in messenger RNA that codes
for a single amino acid
(0.2 for the fact that it's a group of nucleic acid bases; 0.1 for the
fact that it's specifically a triplet; 0.1 for the fact that it codes for
a single amino acid; 0.1 for the fact that it appears specifically in mRNA).
C. Reverse Definitions: 0.5 points each.
- 9. haploid number.
- 10. proto-oncogene. (give 0.2 points for "growth factor gene")
D. Fill in the blanks: 0.5 point each.
- 11. spermatogenesis; oogenesis (in that order).
- 12. differentiation; nuclei; angiogenesis (or vascularization).
E. Short answers: 1 point each.
- 13. (Chapter 18, "Applying your knowledge to the concepts,"
#4):
They develop into identical twins. (0.6 points for "twins").
- 14. (a) 3'-T-G-G-C-T-A-T-A-C-A-T-A-G-G-A-T-C-C-5' (3' and
5' are optional)
(b) ACCGAUAUGUAUCCUAGG
F. Full-paragraph answer: 2 points.
- 15. (a) What blood type is Dr. Howard's father? Why?
Dr. Howard's father must be AB+. A and B are both dominant over O, so the
only way an O mother (who is thus homozygous recessive) can give birth
to both A and B offspring is for the father to be AB. Rh+ is dominant over
Rh-, so with a homozygous recessive mother, the father must be Rh+.
(0.5 point for getting "AB+" or "AB positive"; 0.3
points for "AB" or "AB-". The other 0.5 point is earned
by explaining the result through dominance arguments.)
(b) What difference between Dr. Howard and his mother's blood type is
likely to have caused problems immediately after birth? Why?
The difference in Rh factor causes the problem. Since Dr. Howard's older
sister is also Rh positive, anti-Rh antibodies may have been produced when
she was born, and these might have crossed the placenta and destroyed Dr.
Howard's erythrocytes shortly after birth. This condition of "hemolytic
disease of the newborn" (HDN) was a serious problem in 1954 when Dr.
Howard was born.
(0.5 points for recognizing that the Rh factor difference is the medically
relevant one; 0.5 for describing or naming the nature of the problem).
- 16. Cancer occurs in three stages: initiation, involving as few as
one mutation to a cell; promotion, involving alteration of various control
pathways in the mutated cell, giving rise to clonal replication; and progression,
involving transmission of the tumorous tissue to other parts of the body.
The data given here suggest that cigarette smoking can potentiate the effects
of working in the uranium mine. It is likely that a mutational event caused
by exposure to ionizing radiation in the mine can be moved along the path
toward cancer through the cancer-promoting effects of some of the chemicals
found in cigarette smoke--the so-called "tars". Without the presence
of the cigarette smoke to provide promotional activity, the initiational
events that occur in mining can be repaired without production of cancer.
Cigarette smoke has both initiators and promoters in it, so it can cause
cancer by itself; and it can also bring to fruition the damage caused by
ionizing radiation.
(Score 0.6 points for describing the multi-stage model of carcinogenesis
correctly. Score another 0.6 for associating working in the uranium mine
with increased risk of mutation due to the ionizing radiation to which
the miners are exposed. Score another 0.5 for recognizing that cigarette
smoke is acting as the promoter for the initiative damage caused by the
radiation, and the final 0.3 for recognizing that cigarette smoke also
contains initiators so that it can cause cancer all by itself).