Zoo/Bot 3333
Genetics
Quiz 2
9/29/06
For answers to the quiz, please click here
1. A man has defective tooth enamel, resulting in brown teeth. He marries a normal
woman; all of his sons are normal, but all of his daughters have defective enamel. His
children go on to marry spouses with normal tooth enamel; all of his sons have normal
children, but one-half of his daughter’s children, males and females, have abnormal teeth.
In this problem: a) the disease segregates an autosomal dominant; b) the disease
segregates as an autosomal recessive; c) the disease segregates as a X-linked recessive; d)
the disease segregates as an autosomal gene with incomplete penetrance; e) none of the
above.
2. Tribbles are animals that have a sex determination mechanism similar to humans. The
trait blotchy (b), with pigment in spots, is recessive to solid color (b+), and white color
(w) is recessive to black color (w+). A white, solid female is crossed to a black, blotchy
male. All of the progeny are solid black. If the blotchy trait was sex linked and the white
trait was autosomal, which of the following phenotype frequencies would be expected in
the F2 generation? a) 3/8 black solid females; b) 3/16 black blotchy males; c) 1/8 white
solid females; d) 1/16 white solid males; e) all of the above.
Questions 3-4 refer to the following.
In a group of rabbits, you
discover three different coat
color phenotypes: chinchilla
(C), himalaya (H) and albino
(A). To understand the
inheritance pattern, you
conduct a number of
different crosses between
animals of these phenotypes.
The results are depicted on
the right.
3. True or false. These results indicate that there are two independently assorting gene
loci involved in these phenotypes.
4. If the two chinchilla parents from crosses #7 and #10 are crossed, what progeny ratios
would be produced?
a) ½ C: ½ A; b) all C: c) all H; d) ¾ C: ¼ H; e) none of the above.
5. Wild type strains of the haploid fungus Neurospora can make their own tryptophan.
An abnormal allele td renders the fungus incapable of making its own tryptophan, and
individuals of this genotype will grow only if supplied with tryptophan. The allele su
assorts independently of td; it’s only known effect is to suppress the td phenotype, and
strains carrying both mutant alleles can grow in the absence of tryptophan. If a td;su
strain is crossed to a wild type strain for these genes, what is the ratio of tryptophan
independent to dependent progeny?
a) 9 independent: 7 dependent; b) 3 independent: 1 dependent; c) 3 dependent: 1
independent; d) 1 dependent: 16 independent; e) all independent.
Questions 6-7 pertain to the following. In corn, a triple heterozygote was obtained
carrying the mutant alleles s (shrunken), w (white aleurone), and x (waxy endosperm).
The triple heterozygote was testcrossed, and the progeny contained 116 shrunken, white;
4 fully wild type; 2538 shrunken; 601 shrunken, waxy; 626 white; 2708 white, waxy; 2
shrunken, white, waxy, and 113 waxy.
6. The distance between the white and waxy genes is:
a) 3.5 cM; b) 4.5 cM; c) 18.4 cM; d) 21.9 cM e) 23.5 cM
7. The calculated interference value for this cross is:
a) 0.084; b) .14; c) 0.915; d) 0.86; e) 10.7
Questions 8-9 pertain to the following. The father of Mr. Spock, first officer of the
starship Enterprise, came from the planet Vulcan. Spock’s mother came from Earth. A
Vulcan has pointed ears (determined by allele P), adrenals absent (determined by A) and
a right-sided heart (determined by R). All are dominant to the normal Earth alleles. The
three loci are autosomal, and they are linked as shown in the following linkage map:
A-------------------------10 m.u.---------------P--------------------8 m. u. -----------R
8. If Mr. Spock marries a normal woman, and there is no genetic interference, what
proportion of their children will have Vulcan phenotypes for all three characters?
a)0.05; b) 0.18 c) 0.414; d) 0.82; e) none of the above.
9. What proportion would have Vulcan ears and no adrenals but earth heart?
a). 0.008; b) 0.04; c) 0.046; d) 0.05; e) none of the above.
10. The following asci were obtained in Neurosopora when a wild type strain (td+) was
crossed to a mutant strain unable to grow in the absence of tryptophan (td-).
Spore pair
Ascus type
1-2
td+
tdtdtdtd+
3-4
td+
td+
tdtd+
td5-6
tdtd+
td+
tdtd7-8
tdtdtd+
td+
td+
total
53
7
47
8
5
The distance between the td locus and the centromere is:
a) 5.4 map units; b) 8.3 map units; c) 10.8 map units; d) 16.6 map units; e) none of the
above.