For each of the following determine the percentage of genotypes, genotype terms, and phenotypes.
Monohybrids
1. A homozygous white rabbit (b) is crossed with a heterozygous black rabbit (B).
2. A true breed tall plant is crossed with a short plant. Tall is dominant.
Dihybrid
In kangaroo rats brown color is dominant (B) and white color is recessive. The ability to jump is
dominant (J), the ability to waddle is recessive. If a white, waddling kangaroo rat is mated with a
heterozygous brown, jumping mouse – what are the probabilities of the genotypes and phenotypes of the
offspring.
Intermediate
1. Tulips are incompletely dominant, so red (R) and yellow (Y) are both incompletely dominant traits. If
a hybrid is present, one will see orange tulips. What are the genotype and phenotype percentages of
crossing a pure red with a pure yellow tulip.
2. The lubber grasshopper is a very large grasshopper, and is black with red and yellow stripes. Assume
that red stripes are expressed from the homozygous CR genotype, yellow stripes from the homozygous
CY genotype, and both from the heterozygous genotype. What will be the phenotypic ratio of the F1
generation resulting from a cross of two grasshoppers, one red & one with both red and yellow stripes?
Multiple Alleles
1. In cattle hair color shows codominance. Red CR is dominant, and white CW is recessive. In the
heterozygous condition codominance is shown as a roan (something of a light red) coat. If two roan
cattle are crossed - what is the percent chance of each phenotype? Of each genotype?
2. George is blood type AB. His father was blood type O and his mother was blood type AB. What were
the genotypes of his parents and what are the possible blood types and ratios expected for crosses
involving these parental genotypes? Is George their child?
Polygenic Inheritance
1. Melanin is coded for when the gene L, M, or N is present. The more of these genes are present,
then the darker the skin the individual. The darkest skin possible would be LLMMNN while an
albino would be XXXXXX. Write the following names from darkest to lightest skin.
__________ LXMMXX- Baljeet
__________ LXMXXX- Candace
__________ LLMXNN- Perry
__________ XXMXXX- Ferb
__________ LLMMNN - Phineas
__________ LXMMNX- Isabella
ANSWERS – More Review Part 1
For each of the following determine the percentage of genotypes, genotype terms, and phenotypes.
Monohybrids
1. A homozygous white rabbit (b) is crossed with a heterozygous black rabbit (B).
b
B Bb
b bb
50% Heterozygous Black,
50% homozygous white
b
Bb
bb
2. A true breed tall plant is crossed with a short plant. Tall is dominant.
T
T
t Tt
Tt
t Tt
Tt
100% Heterozygous tall
Dihybrid
In kangaroo rats brown color is dominant (B) and white color is recessive. The ability to jump is
dominant (J), the ability to waddle is recessive. If a white, waddling kangaroo rat is mated with a
heterozygous brown, jumping mouse – what are the probabilities of the genotypes and phenotypes of the
offspring.
BJ
Bj
bJ
bj
bj
BbJj
Bbjj
bbJj
bbjj
bj
BbJj
Bbjj
bbJj
bbjj
bj
BbJj
Bbjj
bbJj
bbjj
bj
BbJj
Bbjj
bbJj
bbjj
BbJj- 25%, brown, jumping
Bbjj- 25%, brown, waddle
bbJj- 25%, white, jumping
bbjj- 25%, white, waddle
Intermediate
1. Tulips are incompletely dominant, so red (R) and yellow (Y) are both incompletely dominant traits. If
a hybrid is present, one will see orange tulips. What are the genotype and phenotype percentages of
crossing a pure red with a pure yellow tulip.
R
R
Y RY
RY
Y RY
RY
100% Heterozygous RY- 100% orange
2. The lubber grasshopper is a very large grasshopper, and is black with red and yellow stripes.
Assume that red stripes are expressed from the homozygous CR genotype, yellow stripes from
the homozygous CY genotype, and both from the heterozygous genotype. What will be the
phenotypic ratio of the F1 generation resulting from a cross of two grasshoppers, one red & one
with both red and yellow stripes?
CR
CR
CR CR CR
CR CR
Y
R Y
C C C
CR CY
50% CRCR - red strip, 50% both CR CY
Multiple Alleles
1. In cattle hair color shows codominance. Red CR is dominant, and white CW is recessive. In the
heterozygous condition codominance is shown as a roan (something of a light red) coat. If two roan
cattle are crossed - what is the percent chance of each phenotype? Of each genotype?
CR
CW
R R
C C C
C R CW
CW CR CW
C W CW
R R
R W
25% red - C C 50% roan-C C 25% white-CW CW
R
2. George is blood type AB. His father was blood type O and his mother was blood type AB. What were
the genotypes of his parents and what are the possible blood types and ratios expected for crosses
involving these parental genotypes? Is George their child?
i
I IA i
IB IB i
Probably not. 50% A, 50% B
A
i
IA i
IB i
Polygenic Inheritance
1. Melanin is coded for when the gene L, M, or N is present. The more of these genes are present,
then the darker the skin the individual. The darkest skin possible would be LLMMNN while an
albino would be XXXXXX. Write the following names from darkest to lightest skin.
______4____ LXMMXX- Baljeet
_____5____ LXMXXX- Candace
______2____ LLMXNN- Perry
_____6____ XXMXXX- Ferb
______1____ LLMMNN - Phineas
_____3____ LXMMNX- Isabella
For each of the following determine the percentage of genotypes, genotype terms, and phenotypes.
Monohybrids
1. A homozygous white rabbit (b) is crossed with a heterozygous black rabbit (B).
2. A true breed tall plant is crossed with a short plant. Tall is dominant.
Dihybrid
In kangaroo rats brown color is dominant (B) and white color is recessive. The ability to jump is
dominant (J), the ability to waddle is recessive. If a white, waddling kangaroo rat is mated with a
heterozygous brown, jumping mouse – what are the probabilities of the genotypes and phenotypes of the
offspring.
Intermediate or Incomplete
1. Tulips are incompletely dominant, so red (R) and yellow (Y) are both incompletely dominant traits. If
a hybrid is present, one will see orange tulips. What are the genotype and phenotype percentages of
crossing a pure red with a pure yellow tulip.
2. The lubber grasshopper is a very large grasshopper, and is black with red and yellow stripes. Assume
that red stripes are expressed from the homozygous CR genotype, yellow stripes from the homozygous
CY genotype, and both from the heterozygous genotype. What will be the phenotypic ratio of the F1
generation resulting from a cross of two grasshoppers, one red & one with both red and yellow stripes?
Multiple Alleles
1. In cattle hair color shows codominance. Red CR is dominant, and white CW is recessive. In the
heterozygous condition codominance is shown as a roan (something of a light red) coat. If two roan
cattle are crossed - what is the percent chance of each phenotype? Of each genotype?
2. George is blood type AB. His father was blood type O and his mother was blood type AB. What were
the genotypes of his parents and what are the possible blood types and ratios expected for crosses
involving these parental genotypes? Is George their child?
Polygenic Inheritance
1.Melanin is coded for when the gene L, M, or N is present. The more of these genes are present, then
the darker the skin the individual. The darkest skin possible would be LLMMNN while an albino would
be XXXXXX. Write the following names from darkest to lightest skin.
__________ LXMMXX- Balzich
__________ LXMXXX- Candace
__________ LLMXNN- Perry
__________ XXMXXX- Ferb
__________ LLMMNN - Phineas
__________ LXMMNX- Isabella
More Monohybrids
1. There are 62 white rabbits and 18 black rabbits. If black (B) is dominant – What are the phenotypes
and genotypes of the parents?
2. A farmer gets 260 Tall plants (T) and 240 short plants from his crop. What are the phenotypes and
genotypes of the parents?