Problemes Genetica

GENETICS PROBLEMS

1.- Black pelage of guinea pigs is a dominant trait; while is the alternative recessive trait. When a pure black guinea pig is crossed to a white one, what fraction of the black F2 is expected to be heterozygous?

2.- Several black guinea pigs of the same genotype were mated and produced 29 black and 9 white offspring. What would you predict the genotypes of the parents tobe?

3.- If a Mack female guinea pig is testcrossed and produces at least one white offspring, determine:
a) The genotype and phenotype of the site (mate parent) that produced the white offspring,
b) the genotype of this female.

4.- Heterozygous black (Bb) guinea pigs are mated to homozygous recessive (bb) whites. Predict the genotypic and phenotypic ratios expected frombackcrossing the black F1 progeny to:
a) the black parent
b) the white parent.

5.- The black hair of guinea pigs is produced by a dominant gene B and white by its recessive allele b. Unless there is evidence to the contrary, assume that II1 and II4 do not carry the recessive allele. Calculate the probability that an offspring of III1 x III2 will have white hair.

6.- Short hair is due to adominant gene S in rabbits, and long hair to its recessive allele s. A cross between a short-haired female and a long-haired male produced a litter of I long-haired and 7 short-haired bunnies.
a) What are the genotypes of the parents?
b) What phenotypic ratio was expected in the offspring generation?
c) How many of the 8 bunnies were expected to be long-haired?

7.- Black wool of sheepis due to a recessive allele w and white wool to its dominant allele W. A white buck (male) is crossed to a white ewe (female), both animals carrying the allele for black. They produce a white buck lamb that is then backcrossed to the female parent. What is the probability of the backcross offspring being black?

8.-In foxes, silver-black coat color is governed by a recessive allele b and redcolor by its dominant allele B.
Determine the genotypic and phenotypic ratios expected from the following matings:
a) pure red x carrier red,
b) carrier red x silver-black,
c) pure red x silver-black.

9.- Yellow coat color in guinea pigs is produced by the homozygous genotype CVCV, cream color by the heterozygous genotype CVCW. and white by the homozygous genotype CWCW. Whatgenotypic and phenotypic ratios are expected in mattings between cream-colored individuals?

10.- When chickens with white feathers are crossed with black-feathered birds, their offspring are all slate blue (Blue Andalusian). When Blue Andalusians are crossed among themselves, they produce while, blue, and black offspring in the ratio of I : 2 : 1, respectively,
a) How are these feather traitsinherited?
b) Using any appropriate symbols, indicate the genotypes for each phenotype.

11.- The shape of radishes may be long {SLSL), round { SRSR), or oval (SLSR). If long radishes are crossed to oval radishes and the F1 then allowed to cross at random among themselves, what phenotypic ratio is expected in the F2?

12.- Black coat color in Cocker Spaniels is governed by a dominant allele Band red coat color by its recessive allele b: solid pattern is governed by the dominant allele of an independently assorting locus S. and sported pattern by its recessive allele, v. A solid-black mate is mated to a solid-red female and produces a litter of 6 pups: 2 solid black. 2 solid red,1I black and white, and 1 red and white. Determine the genotypes of the parents.

13.- A blue eyed man,whose both parents were brown eyed, marries to a brown eyed woman and they produce a blue eyed child. Which aret he genotypes of all the people in this family?

14.- In chickens, rosec rest is dominant upon normal crest. A farmer thinks that one of his rose crest chickens carries the normal crest gene. Is there any method to find it out?

15.- A cross between two pumpkin plants, both with...