1) what is the phenotypic ratio of the offspring produced? horned : no horned

2) what percentage of the offspring will have no horns?

3) in pea plants, purple flowers are dominant to white flowers. if a homozygous dominant plant is crossed with a heterozygous plant what would their offspring look like? complete the punnett square and questions below.

genotypes of parents: and
how many offspring are purple?
how many offspring are white?

4) when pure red flowers mate with pure blue flowers the offspring in the f1 generation have purple flowers. this is an example of incomplete dominance. cross two f1 generation purple flowers. complete the punnett square and answer the questions that follow.

genotypes of both f1 generation flowers: and
what is the phenotypic ratio of the f2 generation? red : : blue

5. red coat color and white coat color are co-dominant in horses. the heterozygous genotype produces a roan coat color (both red and white). cross a pure red coat with a pure white coat. complete the punnett square and answer the questions that follow.

genotypes of the parents: and
what is the genotype of all the offspring?
what is the phenotype of all the offspring?

6. as you read in the online lesson, human blood type is determined by multiple alleles that show a type of inheritance called codominance. recall that the alleles that determine blood type are ia, ib, and i. ia and ib are both dominant over i, while neither ia nor ib is dominant when they combine. use this table to you determine the genotypes associated with each blood type.
blood type (phenotype)

allele

possible genotype(s)

possible allele(s)

a

ia

aa or ao

iaia or iai

b

ib

bb or bo

ibib or ibi

ab

iaib

ab

iaib

o

i

oo

ii

one parent has the genotype iai and the other parent has the genotype ibi. complete a punnett square showing the possible genotypes of their children.

what are the possible phenotypes of the children from this mating?

what are the possible genotypes of the children from this mating?

for a person to have type o blood, what allele combination must s/he receive?

7. color blindness is a sex-linked trait that is carried on the x chromosome. red-green color blindness is caused by the recessive allele “n” and is carried on the x chromosome (xn). when the x chromosome carries the dominant allele “n”, then it is written as xn.

a woman with normal vision, whose father was colorblind, is married to a man whose mother was colorblind.
what is the genotype of the woman with normal vision?

what is the genotype of the man she married?

complete a punnett square to predict the probability of the couple having colorblind children.

what are the chances of producing a colorblind female?

part 2: dihybrid crosses
in dihybrid crosses, there are four alleles for each parent instead because you’re tracking two different traits. the easiest way to determine the alleles for the punnett squares is by using the foil method shown below. the letter combinations circled in blue are the allele combinations that can be given to offspring.

8. one parent has the genotype g g h h. what are the four, two letter allele combinations that this parent can pass to its offspring? make sure to follow each step in the foil method above to determine all the possible allele combinations.

four possible gamete combinations:
9. in mice, black fur (f) is dominant over white fur (f). black eyes (e) are dominant over red eyes (e). both parents in this dihybrid cross are heterozygous for black fur and black eyes. (remember: heterozygous means they have one dominant allele and one recessive allele). look at the punnett square below and fill in the missing offspring.

fe
fe
fe
fe
fe
ffee

ffee

fe
ffee
ffee
ffee
ffee
fe

ffee

ffee
fe
ffee
ffee
ffee

10. imagine that you are crossing two plants that are heterozygous for height and seed color. heterozygous means you have one dominant allele and one recessive allele. the dominant and recessive alleles for these traits are:
tall plant: t yellow seeds: y
short plant: t green seeds: y