Zoo/Bot 3333
Genetics
Quiz 1
8/31/12
For answers to the quiz, click here:
Please choose the single best answer and record in #2 pencil on your scantrons. Please be
sure to answer the questions using the BLUE side of the scantron.
1. A mother and father have 4 children, all girls, and relatives have told them that the
chance that their 5th child will be a boy is very high. What is the probability that a 5th
child born to this family will be a boy?
a) 3l/32; b) 9/10; c) 7/8; d) 3/4; e) 1/2.
Questions 2-3 pertain to the following:
Some species of plants produce two forms that differ in their flowers (termed
heterostylous species). There are two flower forms (termed pin and thrum) of a
heterostylous species of fiddleneck (Amsinckia spectabilis).
The following four pollinations are made:
Parents
pin plant #1 x pin plant #2
thrum plant #3 x thrum plant #3
thrum plant #3 x pin plant #1
Thrum plant #4 x pin plant #2
Progeny
44 pin plants
23 thrum plants
32 thrum plants
20 pins, 17 thrums
The dominant allele of the heterostyle gene can be represented by H and the recessive
allele by h.
2. The genotypes of pin plant #1, pin plant #2, thrum plant #3 and thrum plant #4 (in their
respective order) would be:
a) Hh, HH, hh, H/h; b) hh, hh, HH, H/h; c) HH, HH, Hh, H/h;(d) HH, HH, h/h, Hh;
e) hh, hh, Hh, HH.
3. If thrum plant #4 was crossed to thrum plant #4, what proportion of pins and thrums
would be expected?
a) all thrum; b) 3 pin: l thrum; c) 1 thrum:1 pin; d) 3 thrum:1 pin; e) all pins.
Consider the following genetic cross, where all loci are independently segregating.
AABbCcddEe x AaBbCCDdEe
4. What proportion of the progeny will phenotypically resemble the first (i.e.
AABbCcddEe) parent?
a) 9/32; b) 9/128; c) 27/128; d) 27/256; e) none of the above.
AABbCcddEe x AaBbCCDdEe
5. What proportion of the progeny will phenotypically resemble either parent?
a) 1/32; b) 9/32; c) 27/64; d) 27/32; e) none of the above.
6. What proportion of the progeny will phenotypically resemble neither parent?
a) 5/32; b) 81/216; c) 7/16; d) 37/64; e) none of the above.
7. The CFTR gene:
a) encodes a cytoplasmic protein capable of producing branched starch molecules; b) has
a recessive allele that is responsible for the wrinkled seed phenotype observed in
Mendel’s experiments; c) effects the osmotic pressure in the seed during development; d)
all of the above; e) none of the above.
8. Which of the following statements characterizing human complexity are true?
a) Proteins are made of 100’s to thousands of different types of amino acids; b) the
number of different genes found in the E. coli bacterium is approximately 666 times less
than the human genome; c) a single human gamete cell contains 23 pairs of
chromosomes; d) the haploid human genome contains approximately 3 x 109 base pairs;
e) all of the above.
Questions 9 and 10 pertain to the following. Tay-Sachs disease (TSD) is an autosomal
recessive disorder that leads to neurological deterioration and death often in infancy, well
before reproductive age. You are a genetic counselor interviewing a phenotypically
normal couple with a history of disease in their families. The wife had a maternal uncle
with TSD and it is known that the uncle’s parents were related. The husband had a male
first cousin on his father’s side who died from TSD, and it is known that this first
cousin’s parents were related. There are no other known cases and no other known
instances of consanguinity. Assume that the trait is very rare in the general population.
9. What are the odds that the wife is a carrier of TSD?
a) ¼; b) 1/3; c) ½; d) 2/3; e) none of the above.
10. What is the probability that a child born to this couple would be affected with TSD?
a) 1/9; b) 1/24; c) 1/36; d) 1/48; e) none of the above.