HL Genetics Review
Vocabulary you should know:
heterozygous
homozygous
allele
trait
true breeding
hybrid
locus
dominant
recessive
Punnett square
genotype
phenotype
test cross
monohybrid
dihybrid
multiple alleles
pedigree
carrier
sex linked
incomplete
dominance
linked genes
recombinants
polygenic
inheritance
nondisjunction
nonsense
missense
Law of segregation
Law of independent
assortment
autosomal
chiasmata
Practice Problems:
1. In sesame plants, the one-pod condition (P) is dominant to the three-pod condition (p), and normal leaf (L) is dominant to wrinkled
leaf (l). Pod type and leaf type are inherited independently. Determine the genotypes for the two parents for all possible matings
producing the following offspring:
a) 318 one-pod, normal leaf and 98 one-pod, wrinkled leaf
b) 323 three-pod, normal leaf and 106 three-pod, wrinkled leaf
c) 401 one-pod, normal leaf
d) 150 one-pod, normal leaf, 147 one-pod, wrinkled leaf, 51 three-pod, normal leaf, and 48 3-pod, wrinkled leaf
f) 223 one-pod, normal leaf, 72 one-pod, wrinkled leaf, 76 three-pod, normal leaf, and 27 three-pod, wrinkled leaf
2. Karen and Steve each have a sibling with sickle-cell disease. Neither of them nor any of their parents have the disease, and none of
them have been tested to see if they have the sickle-cell trait. Based on this incomplete information, calculate the probability that if this
couple has a child, the child will have sickle-cell disease.
3. Two pairs of alleles which are inherited independently may interact in such a way that neither dominant can produce its effect unless
the other is present. In sweet peas genes C or P alone produce white flowers, the purple color being due to the presence of both thes
factors. What will be the colors of the offspring of the following cross: CcPp x ccPp. In what proportions? Illustrate with a Punnett
Square.
4. Construct and complete a Punnett square for a dihybrid cross between two A type Rh + people. At the bottom, list the phenotypic
ratios of each blood type.
5. In sweet peas, the the purple flower (P) allele is dominant over red (p) and the long (L) pollen grain shape is dominant over short (l).
In one case a dihybrid cross of these two traits results in 3 purple flower long pollen grain for every 1 red flower short grain type.
Suppose that in a harvest of 1000 plants of the same cross as in part A, the following results were obtained:
746 Purple flowers with Long pollen grains
4 red flowers with Long pollen grains
Explain these results using working.
248 red flowers with short pollen grains
2 Purple flowers with short pollen grains.
HL Genetics Review
Vocabulary you should know:
heterozygous
homozygous
allele
trait
true breeding
hybrid
locus
dominant
recessive
Punnett square
genotype
phenotype
test cross
monohybrid
dihybrid
multiple alleles
pedigree
carrier
sex linked
incomplete
dominance
linked genes
recombinants
polygenic
inheritance
nondisjunction
nonsense
missense
Law of segregation
Law of independent
assortment
autosomal
chiasmata
Practice Problems:
1. In sesame plants, the one-pod condition (P) is dominant to the three-pod condition (p), and normal leaf (L) is dominant to wrinkled
leaf (l). Pod type and leaf type are inherited independently. Determine the genotypes for the two parents for a possible mating
producing the following offspring:
a) 318 one-pod, normal leaf and 98 one-pod, wrinkled leaf
b) 323 three-pod, normal leaf and 106 three-pod, wrinkled leaf
c) 401 one-pod, normal leaf
d) 150 one-pod, normal leaf, 147 one-pod, wrinkled leaf, 51 three-pod, normal leaf, and 48 3-pod, wrinkled leaf
e) 223 one-pod, normal leaf, 72 one-pod, wrinkled leaf, 76 three-pod, normal leaf, and 27 three-pod, wrinkled leaf
2. Karen and Steve each have a sibling with sickle-cell disease. Neither of them nor any of their parents have the disease but Steve has
tested positive for the sickle cell trait. Based on this incomplete information, calculate the probability that if this couple has a child, the
child will have sickle-cell disease.
3. Two pairs of alleles which are inherited independently may interact in such a way that neither dominant can produce its effect unless
the other is present. In sweet peas genes C or P alone produce white flowers, the purple color being due to the presence of both these
factors. What will be the colors of the offspring of the following cross: CcPp x ccPp. In what proportions? Illustrate with a Punnett
Square.
4. Construct and complete a Punnett square for a dihybrid cross between two heterozygous A type Rh + people. At the bottom, list the
phenotypic ratios of each blood type.
5 . In sweet peas, the purple flower (P) allele is dominant over red (p) and the long (L) pollen grain shape is dominant over short (l).
In one case a dihybrid cross of these two traits results in 3 purple flower long pollen grain for every 1 red flower short grain type.
Suppose that in a harvest of 1000 plants of the same cross as in part A, the following results were obtained:
746 Purple flowers with Long pollen grains
4 red flowers with Long pollen grains
Explain these results using working.
248 red flowers with short pollen grains
2 Purple flowers with short pollen grains.
1. a) PPLlx PPLl,
PPLl x ppLl,
PPLl x PpLl
and other options
b) ppLl x ppLl
c) PPLL x ppll,
PPLL x PPLL,
PPLL x PpLl and many other options
d) PpLl x Ppll
e) PpLl x PpLl
2. 0
3. 3 purple, 5 white
4. 9 A+, 3 A-, 3 O+, 1 O-
5. because the genes were linked on the same
chromosome and did not sort independently