Question

1. complete the cross between two pea plant parents that are heterozygous for tall height. tall plants are dominant to short plants. use t for the dominant allele and t for the recessive allele. what are the possible genotypes and phenotypes of the offspring and the percent chance for each?

genotypes:
%:
phenotypes:
%:

1. in guinea pigs, black fur is dominant. if a heterozygous black guinea pig is crossed with a white guinea pig what offspring will the litter contain? include genotypes, phenotypes, and percent chances.

genotypes:
%:
phenotypes:
%:

1. the following punnett square resulted after two individuals were crossed. what would be the parents’ genotypes?

the parents’ genotypes would be ____ and ____.

1. if two parents with dominant phenotypes produce an offspring with a recessive phenotype, then which of the following must be true? prove it using the punnett square to the right. use b for the dominant allele and b for the recessive allele.

a. both parents are heterozygous
b. one parent is heterozygous
c. both parents are homozygous
d. one parent is homozygous

Explanation:

Problem 24

Step1: Define parent genotypes

Parents are heterozygous: $Tt \times Tt$

Step2: Fill Punnett Square

	T	t
t	Tt	tt

Step3: Calculate genotype percentages

• $TT$: $\frac{1}{4} = 25\%$
• $Tt$: $\frac{2}{4} = 50\%$
• $tt$: $\frac{1}{4} = 25\%$

Step4: Calculate phenotype percentages

• Tall ($TT, Tt$): $\frac{3}{4} = 75\%$
• Short ($tt$): $\frac{1}{4} = 25\%$

Problem 25

Step1: Define parent genotypes

Heterozygous black: $Bb$, white (recessive): $bb$; cross: $Bb \times bb$

Step2: Fill Punnett Square

	B	b
b	Bb	bb

Step3: Calculate genotype percentages

• $Bb$: $\frac{2}{4} = 50\%$
• $bb$: $\frac{2}{4} = 50\%$

Step4: Calculate phenotype percentages

• Black fur ($Bb$): $50\%$
• White fur ($bb$): $50\%$

Problem 26

Step1: Analyze Punnett Square

Offspring: $TT, Tt, TT, Tt$. One parent contributes only $T$, the other contributes $T$ and $t$.

Step2: Identify parent genotypes

Parent 1: $TT$, Parent 2: $Tt$

Problem 27

Step1: Define recessive offspring genotype

Recessive phenotype = $bb$, so each parent must pass a $b$ allele.

Step2: Set up parent cross

Parents have dominant phenotype, so they must have at least one $B$. Cross heterozygous parents: $Bb \times Bb$

Step3: Fill Punnett Square

	B	b
b	Bb	bb

Step4: Verify conclusion

Only heterozygous parents can produce a recessive offspring.

Answer:

1. Problem 24

• Genotypes: $TT$ (25%), $Tt$ (50%), $tt$ (25%)
• Phenotypes: Tall (75%), Short (25%)

1. Problem 25

• Genotypes: $Bb$ (50%), $bb$ (50%)
• Phenotypes: Black fur (50%), White fur (50%)

1. Problem 26

• The parents' genotypes would be $TT$ and $Tt$

1. Problem 27

• A. Both parents are heterozygous
• Punnett Square confirms this cross produces a 25% chance of recessive $bb$ offspring, which matches the scenario.