Download Review Packet - Mendelian Genetics Practice Problems ANSWER

Eastern Regional High School
Honors Biology
Name:___________________________
Period:________ Date:______________
Unit 12 – Mendelian Genetics
Review Packet – Practice Problems
One Factor Problems:
1. The ability to taste the chemical PTC is determined by a single gene in humans. The ability to taste the
gene is dominant and the inability to taste the chemical is recessive. Suppose two hybrid tasters have a
large family.
a. Predict the proportion of their children who will be tasters and non-tasters. Use the Punnett
square below to make your prediction.
T
t
T
TT
Tt
t
Tt
tt
75% Tasters
25% Non- tasters
b. What is the likelihood that their first child will be a taster?
3/4 or 75%
c. What is the likelihood that their fourth child will be a taster?
3/4 or 75%
2. In a certain plant species, blue flower color is dominant to white. You have a blue flowered plant and a
white flowered plant.
a. What do you know about the genotype of each plant in the P Generation?
Blue = BB or Bb
White= bb
b. Now you cross these plants and ALL the F1 offspring are blue. What have you learned about the
genotypes of the parents?
Must be BB
c. Cross two plants from the F1 generation. Use the Punnett Square below and predict what
percentage of the offspring will be white and what percentage will be blue.
B
b
B
BB
Bb
b
Bb
bb
75% Blue
1
d. What is the genotypic ratio from the Punnett Square above?
1:2:1
3. If you crossed a heterozygous spotted lizard with a homozygous green lizard, what percentage of their
offspring would be green and what percentage would be spotted?
L
50% Spotted
50% Green
l
l
Ll
ll
l
Ll
ll
4. The ability to roll your tongue is dominant over the inability to do so in humans. If two heterozygous
tongue rollers have children, what genotypes and phenotypes could their children have?
T
t
Geno- TT, Tt, tt
Pheno- Tounge Roller, Nonroller
TT
Tt
Tt
tt
5. If a non-tongue roller has children with a homozygous tongue roller, what genotypes and phenotypes their
children have?
Geno- Tt
Pheno- Tounge roller
T
T
Tt
Tt
2
Tt
tt
Two Factor Practice Problems:
AaGG
AaGg
AaGg
Aagg
AG
Ag
1. Cross two pea plants, one that is homozygous axial and
hybrid for seed coat and the other plant has
terminal flowers and is also hybrid for seed coat.
aG
Flower Position:
Axial (A) is dominant to Terminal (a)
ag
Seed Coat:
Gray (G) is dominant to White (g)
a. Write the genotypes of the parents:
AAGg and aaGg
b. List the possible phenotypes of the offspring:
Axial grey, axial white
c. If possible, give the phenotypic ratio:
3:1
d. List the probability of each phenotype occurring in a percentage:
75% A+G
25% A+W
e. If 80 of the seeds are collected from the plants in the cross above, how many of the the seeds would
be axial? Gray? Terminal and Gray?
100% Axial- 80 seeds
75% Gray- 60 seeds
2. A tomato plant that is heterozygous for red fruit and
has a short stem and crossed with a tomato plant that
is purebred for yellow fruit and is hybrid for a long
stem.
Rs
rs
a. Write the genotypes of the parents:
Rrss and rrSs
rS
b. List the possible phenotypes of the offspring:
rS
Red+Long Red+Short Yellow+Long Yellow+Short
c. If possible, give the phenotypic ratio:
3
RrSs
rrSs
Rrss
rrss
0% T+G
1:1:1:1
d. If you collect 160 seeds from this cross, how many of them would give red fruit? How many would
give long stems and yellow fruit?
50% Red=80 seeds
Long + Yellow= 25% = 40
seeds
4
3. In guinea pigs, black hair is dominant over white hair and long hair is dominant over short hair. A
homozygous black and longhaired guinea pig is crossed with a homozygous white, shorthaired guinea pig.
a. Write the genotypes of the parents (P):
BBHH and bbhh
BH
bh
b. Use the punnet square and then list the
phenotypes and genotypes of the offspring:
BbHh
All Black+ Long haired’
All Dirty Bred
c. Two of the offspring from the F1 generation were mated and produced new guinea pigs (F2).
d. Write the genotypes of the parents (F1):
e. Use the punnet square and then list the
phenotypes of the F2 generation:
DiHybrid!
Black+Long haired- 9
Black+ Shorhaired -3
White+ Long haired -3
White + shorthaired -1
f.
What percentage of the F2 guinea pigs will have white, long hair?
18.75%
5
9:3:3:1