Download genetics mendelian genetics

1
Genetics 3500 Fall2014 Test III
3 marks
In rabbits, an allelic series helps to determine coat color: C (full color), cch
(chinchilla; gray color), ch (Himalayan; white with black extremities), and c (albino;
all white). The C allele is dominant to all others, cch is dominant to ch and c, ch is
dominant to c, and c is recessive to all the other alleles. This dominance hierarchy
can be summarized as C > cch > ch > c. Indicate the phenotypic ratios expected if
rabbits with the cross Ccch × Cch.
3 marks
In chickens a rare mutation produces a condition known as “creeper “where by the
bird has short legs and shorter wings and appears to be creeping as it walks. If
creepers are bred to normal chickens about half are creeper and half appear to be
normal. A male creeper and female creeper were bred together and 10 eggs were
collected and hatched . Three of the eggs were normal and 7 were creepers. Creeper
were never true breeding. The progeny of 4 such crosses produced offspring in the
ratio of 25 normal and 53 creepers. Propose an explanation.
3marks
Coat color is determined by two loci in large cats. Two pink panthers fall in love and
produce a large litter of baby panthers with the following phenotypic ratios: 12/16
pink; 3/16 black; and 1/16 white. What is the genotype of the pink progeny?
2
5 marks
Colored aleurone in the kernels of corn is due to the dominant allele R. the recessive
allele produces coloress aleurone. The plant color ( not kernel color is controlled by
a second gene Y an y . the dominant Y allele results ingreen color whereas the
homozygous present of the recessive y allele causesa the plant ot appear yellow ina
test cross between a plant of unknown genotype land [henotype and a plant
recessive for both traits. The following progeny were obtained.
Colored,green 88
Coloed yellow 12
Colorless ,green 8
Colorless yellow 92
Explain how the results were obtained by determining the exact genotype and
phenotype of the unknown plant including the precise association of the two genes
on the homologs (ie: ARRANGEMENT ON THE CHROMOSOME)
2marks
DEFINE THE TERM LINKAGE.
3
6 marks
In radishes flower color may be red, purple or white. The edible portion of a radish
may be long or oval . When only flower color is studied, no dominance is evident;
red and white crosses yield all purple. If these F1 purples are interbred, the F2
generation are ¼ red ½ purple and ¼ white. With respect to shape, oval is dominant
over long.
Determine the F1 and F2 genotypes from a cross between a true breeding red, long
radish and one that is white and oval. Be sure to define the gene symbols that you
are using.
4marks
In cats yellow coat color is determined by the b allele and black coat color is
determined by the B allele the heterozygous condition results in tortoiseshell. These
genes are X linked. What kinds of offspring are generated by a black tom cat mating
with a tortoiseshell female?
4
6 marks
Fruitflies typically have red eyes. While vemillion eyesis X linked in a drosophila and
causes eye color to be bright red, brown is an autosomal recessive mutation that
causes the eye to be brown. Flies carrying both mutations lose all pigmentation and
are white eyed. Predict F1 and F2 of this cross
Homozygous brown females x homozygous vermilion males.
5+ 2 marks
In cattle coats may be solid white, solid black, or black and white spotted. When true
breeding solid whites are mated with true breeding solid blacks, the 1st generation
is all solid white individuals. The F2 generation generated the following results
25 solid white
7 black and white spotted
2 solid black
explain the mode of inheritance by determining the number of genes involved and
which genotypes yield which phenotypes.
Is it possible to have true breeding black and white spotted cattle? If so what would
their genotypes be?
5
3 marks
There are blue-flowered, short-stalked plants (++++) and white-flowered, long-stalked
plant (ffss). The resulting F1 offspring of this cross (++fs) are also crossed to produce
the following F2 progeny:
400 blue, short
400 white, long
100 blue, long
100 white, short
What is the recombination frequency, as shown in the F2 generation?
4 marks
Consider three independently assorting gene pairs A/a, B/b C/c What is the
percentage of offspring that will be AABbCc from parents that are AaBbCC and
AABbCc?
4 marks
In drosophila gray body is dominant over ebony body color while long wings are
dominant over vestigial wings Work the following cross through the F2generation
and determine phenotype ratios
Gray vestigial vs ebony, long