11. Explain why your chosen cross in problem 10 will produce the
most stripped offspring. Use homozygous and heterozygous
terms in your answer.
Crossing a homozygous allele 1 with a homozygous of
allele 2 produces all heterozygous offspring because
each parent can only provide 1 type of allele, either
allele 1 or allele 2.
The following four offspring percentages work for complete dominance, incomplete dominance, and codominance.
12. What is the percentage of homozygous allele 1 or homozygous 2, or heterozygous that always occurs with this cross:
homozygous allele 1 x heterozygous?
50% homozygous allele 1 (genotype) w/trait 1 (phenotype)
50% heterozygous (genotype) w/the blended trait (phenotype)
13. What is the percentage of homozygous allele 1 or homozygous 2, or heterozygous that always occurs with this cross:
homozygous allele 2 x heterozygous?
50% homozygous allele 2 (genotype) w/trait 2 (phenotype)
50% heterozygous (genotype) w/the blended trait (phenotype)
Codominance
Name:
As we saw before (Incomplete Dominance) SpongeBob loves growing flowers for his pal Sandy. SponageBob also grows his favorite
flower the Flootters. He grows all three types: red, blue, and red
flowers with blue spots.
1. What letter are you using for the red allele (allele 1)?
R
2. What letter are you using for the blue allele (allele 2)?
B
3. Complete the chart below
Phenotype
Genotype
Homozygous allele 1
RED
RR
Homozygous allele 2
BLUE
BB
RED W/BLUE SPOTS
BR
Heterozygous
For each cross write
• the genotype of the parental cross
• complete the Punnett square
• list the genotype and phenotype with % of possible offspring.
• answer any additional questions as well.
4. Red flootter crossed with a spotted flootter
RR x BR
14. What is the percentage of homozygous allele 1 or homozygous 2, or heterozygous that always occurs with this cross:
heterozygous x heterozygous?
genotype of parental cross
50% BR spotted
50% RR red
25% homozygous allele 2 (genotype) w/trait 2 (phenotype)
50% heterozygous (genotype) w/the blended trait (phenotype)
25% homozygous allele 1 (genotype) w/trait 1 (phenotype)
phenotype
genotype
percentage
4
Punnett Square
1
For the remaining questions, Punnett squares are NOT required. All
other directions remain the same.
5. Two heterozygous flootters
BR X BR
50% BR spotted
SpongeSal is going jellyfish fishing. The tastiest jellyfish are the
black with yellow stripes. The other jellyfish, yellow and black taste
OK, but Sal prefers the stripped one, which is heterozygous for the
trait.
25% RR red
7. What letter are you using for the black allele (allele 1)?
25% BB blue
B
8. What letter are you using for the yellow allele (allele 2)? Y
9. Complete the chart below
Phenotype
Genotype
Homozygous allele 1
black
BB
Homozygous allele 2
yellow
YY
black w/yellow stripes
BY
Heterozygous
6. Sponge Bob has a field that he planted with homozygous blue
flowers with a heterozygous flowers. If he planted 1600 seeds
from this cross, how many of each color flower would be in the
field?
BB x BR
50% BB blue and 50% BR spotted
10. Sal is stocking a jellyfish fishing hole and trying to produce the
MOST stripped jellyfish as possible.
Determine which cross will give her the most stripped offspring.
•
•
•
•
yellow crossed with stripped
yellow crossed with black
stripped crossed with stripped
stripped crossed with black
BB x YY
800 blue flowers
100% offspring BY stripped
800 spotted flowers
2
3