Question

punnett squares worksheet - pea plant genetics

1. yellow seeds are dominant over green seeds in pea plants. fill in the punnett square and determine

the expected genotypes and phenotypes along with the probabilities from crossing homozygous
recessive and homozygous dominant parents.
key:
y = yellow
y = green
f₁ generation
possible genotypes of offspring: _____________
possible phenotypes of offspring: _____________
percentage of offspring that are yellow: ____% green: ____%
% of offspring that are homozygous dominant: ______%
heterozygous: ____% homozygous recessive: ____%
if there were 100 seeds collected, predict how many would be yellow? ____, green? ____
predict how many seeds would be homozygous dominant? ____, heterozygous? ____,
homozygous recessive: ______

1. green pod color is dominant over yellow pod color in pea plants. fill in the punnett square and

determine the probabilities from crossing homozygous dominant and heterozygous parents.
key:
g = green
g = yellow
possible genotypes: ______
% of offspring that will be green? ____% and be yellow? ____%
% of offspring that are homozygous dominant: ______%
heterozygous: ____% homozygous recessive: ____%
if there were 200 seeds collected, predict how many would be green? ____, yellow? ____
predict how many seeds would be homozygous dominant? ____, heterozygous? ____,
homozygous recessive: ______

1. round seeds are dominant over wrinkled seeds in pea plants. fill in the punnett square and determine

the expected probabilities from crossing homozygous recessive and heterozygous parents.
key:
r = round
r = wrinkled
possible phenotypes: _____________
% of offspring that will be green? ____% and be yellow? ____%
% of offspring that are homozygous dominant: ______%
heterozygous: ____% homozygous recessive: ____%
if there were 3500 seeds collected, predict how many would be round? ____, wrinkled? ____
predict how many seeds would be homozygous dominant? ____, heterozygous? ____,
homozygous recessive: ______

Answer:

Problem 1: Yellow vs Green Seeds (Homozygous Recessive × Homozygous Dominant)

Step 1: Determine Parental Genotypes

• Homozygous recessive parent: \( yy \) (green seeds)
• Homozygous dominant parent: \( YY \) (yellow seeds)

Step 2: Fill Punnett Square

	\( Y \)	\( Y \)
\( y \)	\( Yy \)	\( Yy \)

Step 3: Analyze Offspring

• Possible Genotypes: All \( Yy \) (heterozygous)
• Possible Phenotypes: All yellow (since \( Y \) is dominant)
• Percentages:
• Yellow: \( 100\% \), Green: \( 0\% \)
• Homozygous dominant (\( YY \)): \( 0\% \)
• Heterozygous (\( Yy \)): \( 100\% \)
• Homozygous recessive (\( yy \)): \( 0\% \)
• For 100 seeds:
• Yellow: \( 100 \times 100\% = 100 \)
• Green: \( 100 \times 0\% = 0 \)
• Homozygous dominant: \( 100 \times 0\% = 0 \)
• Heterozygous: \( 100 \times 100\% = 100 \)
• Homozygous recessive: \( 100 \times 0\% = 0 \)

Problem 2: Green vs Yellow Pods (Homozygous Dominant × Heterozygous)

Step 1: Determine Parental Genotypes

• Homozygous dominant parent: \( GG \) (green pods)
• Heterozygous parent: \( Gg \) (green pods)

Step 2: Fill Punnett Square

	\( G \)	\( g \)
\( G \)	\( GG \)	\( Gg \)

Step 3: Analyze Offspring

• Possible Genotypes: \( GG \) (homozygous dominant) and \( Gg \) (heterozygous)
• Possible Phenotypes: All green (since \( G \) is dominant)
• Percentages:
• Green: \( 100\% \), Yellow: \( 0\% \)
• Homozygous dominant (\( GG \)): \( 50\% \)
• Heterozygous (\( Gg \)): \( 50\% \)
• Homozygous recessive (\( gg \)): \( 0\% \)
• For 200 seeds:
• Green: \( 200 \times 100\% = 200 \)
• Yellow: \( 200 \times 0\% = 0 \)
• Homozygous dominant: \( 200 \times 50\% = 100 \)
• Heterozygous: \( 200 \times 50\% = 100 \)
• Homozygous recessive: \( 200 \times 0\% = 0 \)

Problem 3: Round vs Wrinkled Seeds (Homozygous Recessive × Heterozygous)

Step 1: Determine Parental Genotypes

• Homozygous recessive parent: \( rr \) (wrinkled seeds)
• Heterozygous parent: \( Rr \) (round seeds)

Step 2: Fill Punnett Square

	\( R \)	\( r \)
\( r \)	\( Rr \)	\( rr \)

Step 3: Analyze Offspring

• Possible Phenotypes: Round (\( Rr \)) and wrinkled (\( rr \))
• Percentages:
• Round: \( 50\% \), Wrinkled: \( 50\% \)
• Homozygous dominant (\( RR \)): \( 0\% \)
• Heterozygous (\( Rr \)): \( 50\% \)
• Homozygous recessive (\( rr \)): \( 50\% \)
• For 3500 seeds:
• Round: \( 3500 \times 50\% = 1750 \)
• Wrinkled: \( 3500 \times 50\% = 1750 \)
• Homozygous dominant: \( 3500 \times 0\% = 0 \)
• Heterozygous: \( 3500 \times 50\% = 1750 \)
• Homozygous recessive: \( 3500 \times 50\% = 1750 \)

Final Answers (Summarized)

Problem 1:

• Genotypes: \( Yy \)
• Phenotypes: Yellow
• Percentages: Yellow (100%), Green (0%); Homozygous dominant (0%), Heterozygous (100%), Homozygous recessive (0%)
• 100 seeds: Yellow (100), Green (0); Homozygous dominant (0), Heterozygous (100), Homozygous recessive (0)

Problem 2:

• Genotypes: \( GG, Gg \)
• Phenotypes: Green
• Percentages: Green (100%), Yellow (0%); Homozygous dominant (50%), Heterozygous (50%), Homozygous recessive (0%)
• 200 seeds: Green (200), Yellow (0); Homozygous dominant (100), Heterozygous (100), Homozygous recessive (0)

Problem 3:

• Phenotypes: Round, Wrinkled
• Percentages: Round (50%), Wrinkled (50%); Homozygous dominant (0%), Heterozygous (50%), Homozygous recessive (50%)
• 3500 seeds: Round (1750), Wrinkled (1750); Homozygous dominant (0), Heterozygous (1750), Homozygous recessive (1750)