GENERAL GENETICS (BIOL 3024) – VAN DEN BUSSCHE – PROBLEM SET 1 & 2 – FALL 2004
1. Human cells normally have 46 chromosomes. For each of the following stages, state the number of
chromosomes present in a human cell: (a) metaphase of mitosis, (b) metaphase I of meiosis, (c) telophase
of mitosis, (d) telophase I of meiosis, (e) telophase II of meiosis (in you answers, count chromatids as
chromosomes).
2. Four of the following events are part of both meiosis and mitosis, but one is only meiotic. Which is
found only in meiosis?
a.
b.
c.
d.
e.
Chromatid formation
Spindle formation
Chromosome condensation
Chromosome movement to poles
Chromosome pairing
3. Black coat of guinea pigs is caused by the dominant allele “B”; white coat is the alternative condition
and is caused by the recessive allele “b”. You cross a true breeding black-coated guinea pig with a white
coated guinea pig to produce the F1 generation. You then cross the F1 generation. (a) What is the F2
genotypic ratio? (b) What is the F2 phenotypic ratio?
4. In rabbits, short-haired is due to a dominant allele “L”, and long hair is due to the recessive allele “l”.
A cross between a short-haired female and a long-haired male produces a litter of one long-haired and
seven short-haired bunnies. (a) What are the genotypes of the parents? (b) What phenotypic ratio was
expected in the F1 generation? (c) How many of the eight bunnies were expected to be long-haired?
5. (3 POINTS) In rabbits, short hair is governed by the allele “L” and long hair by the allele “l”. Black
hair results from the action of the dominant genotype “B-“ and brown from the recessive genotype “bb”.
You perform the following cross: LlBb X LlBb.
a.
b.
c.
d.
e.
f.
What is the phenotypic ratio from this cross?
What fraction of the F1 individuals breed true?
What fraction of the F1 is heterozygous for both loci?
What fraction of the F1 can be used for test cross purposes?
What fraction of the F1 can be used for test cross purposes for the B locus?
What fraction of all black F1 individuals will breed true for both black and short hair?
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6. (2 POINTS) The normal eye color of Drosophila is red, but strains in which all flies have brown eyes
are available. Similarly, wings are normally long, but there are strains with short wings. A female from a
pure line with brown eyes and short wings is crossed with a male from a normal (red eyes, long wings)
pure line. The F1 consists of normal females and short-winged males. An F2 generation is then produced
by crossing the F1’s. Both sexes of the F2 flies show the phenotypes as follows:
3/8 red eyes, long wings
3/8 red eyes, short wings
1/8 brown eyes, long wings
1/8 brown eyes, short wings.
a. Deduce the mode of inheritance of these phenotypes, using clearly defined genetic symbols of
your own invention.
b. What are the genotypes of the P male and female
c. What are the genotypes of the F1 males and females used to produce the F2
d. As complete as possible, write out the genotypes of the F2 offspring.
7. In peaches, the allele “F” codes for “fuzzy” skin and the allele “f” codes for “smooth” skin. At an
independently assorting locus, the heterozygous conditions of oval glands at the base of the leaves (GO)
and no glands (GN) produces round glands. A homozygous fuzzy, no-gland peach variety is bred to a
smooth, oval gland variety.
a. What will be the appearance of the F1?
b. If the F1 are bred together, what will be the F2 phenotypic ratio?
c. What will be the phenotypic ratio from the cross of the F1 back to the smooth, ovalglanded parent?
8. In guinea pigs, short hair (L) is dominant to long hair (l), and the heterozygous condition of yellow
coat (CY) and white coat (CW) produces a cream coat. A short haired, cream guinea pig is bred to a longhaired, white guinea pig, and a long-haired, cream baby guinea pig is produced. When the baby grows
up, it is bred back to the short-haired, cream parent. What is the expected phenotypic ratio from this
cross?
9. (3 POINTS) In poultry, the dominant alleles for rose comb (R) and pea comb (P), if present together
produce walnut comb. The recessive alleles for each gene, when present together in a homozygous state,
give a single comb.
a. In another mating, a rose-combed individual is crossed with a walnut combed individual
and produce offspring with the following phenotypic ratio: 3/8 walnut, 3/8 rose, 1/8 pea, and
1/8 single. What are the genotypes of the parents?
b. Parents of unknown genotype and phenotype are crossed and produce offspring with the
following phenotypic ratio: 1/4 walnut, 1/4 rose, 1/4 pea, and 1/4 single. What are the
genotypes of the parents?
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10. In addition to the traits described in problem #9, feathered shanks (F) are dominant to clean shanks
(f), and white plumage (I) is dominant to black (i). A feathered-shanked, white, rose-combed bird is
crossed with a clean-shanked, white, walnut-combed bird and produces these offspring:
2 feathered, white, rose
4 clean, white, walnut
3 feathered, black, pea
1 clean, black, single
1 feathered, white, single
2 clean, white, rose
What are the genotypes of the parents that produced these offspring?
11. A locus in mice is involved with pigment production; when parents heterozygous at this locus are
mated, 3/4 of the progeny are colored and 1/4 are albino. Another phenotype concerns the coat color
produced in mice; when two yellow mice are mated, 2/3 of the progeny are yellow and 1/3 are agouti.
The albino mice cannot express whatever alleles they may have at the independently assorting agouti
locus. When yellow mice are crossed with albino mice, they produce and F1 consisting of 1/2 albino, 1/3
yellow, and 1/6 agouti. What are the probable genotypes of the parents?
12. (2 POINTS) In sheep, white fleece (B) is dominant over black (b) and horned (H) is dominant over
hornless (h) in males but recessive in females. A horned white ram is bred to the following four ewes and
has one offspring by the first three and two by the fourth: Ewe A is hornless and black; the offspring is a
horned white female. Ewe B is hornless and white; the offspring is a hornless black female. Ewe C is
horned and black; the offspring is a horned white female. Ewe D is hornless and white; the offspring are
one hornless black male and one horned white female. What are the genotypes of the five parents?
13. In Drosophila, a mutant strain has plum-colored eyes. A cross between a plum-eyed male and a
plum-eyed female produces 2/3 plum-eyed and 1/3 red-eyed (wild-type) progeny flies. A second mutant
strain of Drosophila, called stubble, has short bristles instead of normal long bristles. A cross between a
stubble female and a stubble male gives 2/3 stubble and 1/3 normal-bristled flies in the offspring.
Assuming that the plum gene assorts independently from the stubble gene, what will be the genotypic and
phenotypic ratio resulting from a cross of two plum-eyed, stubble bristled flies?
14. A heterozygous genetic condition called “creeper” in chickens produces shortened and deformed legs
and wings, giving the bird a squatty appearance. Matings between creepers produced 775 creeper:388
normal progeny. Do these data fit the hypothesis of a 3:1 ratio? Test at the p = 0.05 level. In your
answer, give the calculated 2- value and your conclusion.
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Answer Sheet: ONLY TURN IN YOUR ANSWER SHEET. YOU SHOULD KEEP THE QUESTIONS TO HELP WHEN WE
COVER THE QUESTIONS IN CLASS. ANSWERS ARE DUE BEFORE THE BEGINNING OF CLASS ON FRIDAY 3
SEPTEMBER 2004. ALTERNATIVELY, ANSWERS MAY BE SLID UNDER MY OFFICE DOOR (LSW 411) PRIOR TO 3
SEPTEMBER. ANSWERS TURNED IN AFTER THE START OF CLASS ON FRIDAY (9-3-04) WILL NOT BE GIVEN
CREDIT.
1a. ______________
1b. ______________
1c. ______________
1d. ______________
1e. ______________
2.
3a. F2 genotypic ratio
3b. F2 phenotypic ratio
4a.
Genotype of short-haired female:_______________________________
Genotype of long-haired male:_________________________________
4b.
Expected F1 phenotypic ratio:
4c.
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5a.
5b.
5c.
5d.
5e.
5f.
6a.
Symbol for “red-eyes”:_____________________________
Symbol for “brown-eyes”:__________________________
Mode of inheritance for eye color:__________________________
Symbol for “long-wings”:__________________________
Symbol for “short-wings”:_________________________
Mode of inheritance of wing length:________________________
6b.
Genotype of P male:__________________________
Genotype of P female:_________________________
6c.
Genotype of F1 females:________________________
Genotype of F1 males:_________________________
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6d.
7a.
Appearance of F1:
7b.
F2 phenotypic ratio:
7c.
8.
9a.
Genotype of rose-comb individual:____________________________
Genotype of walnut-comb individual:__________________________
9b.
10.
Genotype of Feathered-shanked, white, rose-combed individual:___________________________
Genotype of Clean-shanked, white, walnut-combed individual:____________________________
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11.
Genotype of Yellow Parents:_________________________________
Genotype of Albino Parents:_________________________________
12.
13.
Genotype of Horned white ram:
Genotype of Ewe A:
Genotype of Ewe C:
Genotype of Ewe B:
Genotype of Ewe D:
Genotypic Ratio:
Phenotypic Ratio
14.
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