Download DIHYBRID GENETICS PROBLEMS - Answers 1 In garden peas, tall

DIHYBRID GENETICS PROBLEMS - Answers
1
In garden peas, tall (T) vine is dominant over short (t) vine, and round pea pod (R) is
dominant over wrinkled pea pod (r). Cross a homozygous tall, round pea plant with a
homozygous short, wrinkled pea plant. Show the genotypes and phenotypes of the F1 offspring,
and the probability of each.
Genotype of the homozygous tall, round pea plant = TTRR
Genotype of the homozygous short, wrinkled pea plant = ttrr
Genotype of the offspring = 16/16 TtRr
Phenotype of the offspring = 16/16 Tall and round
2
In garden peas, tall (T) vine is dominant over short (t) vine. Yellow (Y) seed color is
dominant over green (y) seed color. Cross a heterozygous tall, yellow seeded plant with a
heterozygous tall, yellow seeded plant.
Genotypes of the parent plants = TtYy and TtYy
Genotypes of the offspring =
1/16 TTYY
2/16 TTYy
1/16 TTyy
2/16 TtYY
4/16 TtYy
2/16 Ttyy
1/16 ttYY
2/16 ttYy
1/16 ttyy
Phenotypes of the offspring:
9/16 Tall and yellow
3/16 Tall and green
3/16 short and yellow
1/16 short and green
What is the probability for a tall offspring?
12/16
What is the probability for a short offspring?
What is the probability for a yellow offspring?
4/16
12/16
What is the probability for a green offspring?
4/16
What is the probability for a tall yellow offspring? 9/16
What is the probability for a tall green offspring?
3/16
What is the probability for a short yellow offspring? 3/16
What is the probability for a short green offspring? 1/16
3
A heterozygous tall yellow plant is crossed with a homozygous short green. What will be
the genotypes and phenotypes, and probabilities of the first generation?
Genotype of the heterozygous tall, yellow plant = TtYy
Genotype of the homozygous short, green plant = ttyy
Genotypes of the offspring:
¼ TtYy
¼ Ttyy
¼ ttYy
¼ ttyy
Phenotypes of the offspring:
¼ tall and yellow
¼ tall and green
¼ short and yellow
¼ short and green
4
Right handedness (R) is dominant over left (r). Brown eyes (B) are dominant over blue
(b). A man who is blue eyed and right handed, whose father was left handed, married a left
handed woman with brown eyes, whose mother was blue eyed. What are the possible
phenotypes and genotypes of the offspring and the probability for each?
Genotype of the man = bbRr
Genotype of the woman = Bbrr
Genotypes of the offspring:
¼ BbRr
¼ Bbrr
¼ bbRr
¼ bbrr
Phenotypes of the offspring:
¼ Brown eyed and right handed
¼ Brown eyed and left handed
¼ blue eyed and right handed
¼ blue eyed and left handed
What is the probability of getting right handed offspring? 2/4
What is the probability of getting blue eyed offspring? 2/4
What is the probability of getting offspring heterozygous for both traits? 1/4
What is the probability of getting offspring that are homozygous dominant? 0
5
The ability to taste PTC paper is controlled by a dominant gene. The ability to taste (T)
PTC is dominant over the inability to taste (t) PTC. Normal skin (N) is dominant over albino
skin (n). Two tasters, normally pigmented have an albino son and a non-taster daughter. Show
the cross between the parents.
Genotype of mom = TtNn
Genotypes of the offspring:
1/16 TTNN
2/16 TTNn
1/16 TTnn
2/16 TtNN
4/16 TtNn
2/16 Ttnn
Genotype of dad = TtNn
1/16 ttNN
2/16 ttNn
1/16 ttnn
Phenotypes of the offspring:
9/16 Tasters with Normal skin
3/16 Tasters with albino skin
3/16 Nontasters with Normal skin
1/16 Nontasters with albino skin
What is the chance that the albino son is a taster? 3/16
What is the chance that the non-taster daughter is an albino? 1/16
What is the chance that the non-taster daughter is a carrier of the albino trait? 2/16
What is the chance of getting offspring who are heterozygous for both traits? 4/16
6
Let’s assume that the non-taster, daughter in question 5 is a carrier of the albino trait.
She marries a taster man, normally pigmented, whose mother was a non-taster albino. Show the
cross between these parents.
Genotype of the woman
Genotypes of the offspring
2/16 TtNN
4/16 TtNn
2/16 Ttnn
= ttNn
Genotype of the man = TtNn
2/16 ttNN
4/16 ttNn
2/16 ttnn
Phenotypes of the offspring:
6/16 Tasters with normal skin
2/16 Tasters with albino skin
6/16 Nontasters with normal skin
2/16 Nontasters with albino skin
What is the chance that their child will be a taster?
8/16
What is the chance that their child will be albino? 4/16
What is the chance that their child will be a taster albino? 2/16
7
A normally pigmented woman who is a non-taster has a father who is an albino taster.
She marries an albino man who is a taster, but who has a mother who is a non-taster. Show the
types of children this couple may have and the probability of each.
What is the genotype of the woman? = ttNn
man? = Ttnn
Genotypes of the offspring:
4/16 TtNn
4/16 Ttnn
4/16 ttNn
4/16 ttnn
What is the genotype of the
Phenotypes of the offspring:
4/16 Tasters with normal skin
4/16 Tasters with albino skin
4/16 Nontasters with normal skin
4/16 Nontasters with albino skin
8
Some dogs bark when trailing, others are silent. Barking while trailing (B) is dominant to
the silent trailer (b). Erect ears (E) are dominant to drooping ears (e). What kinds of pups
would be expected from a heterozygous, erect-eared barker mated to a droop-eared silent trailer?
Genotype of the heterozygous, erect-eared barker? = EeBb
Genotype of the droop-eared, silent trailer? = eebb
Genotypes of the offspring:
4/16 EeBb
4/16 Eebb
4/16 eeBb
4/16 eebb
Phenotypes of the offspring:
4/16 Erect eared barkers
4/16 Erect eared silent trailers
4/16 Droopy eared barkers
4/16 Droopy eared silent trailers