Question

if tall plants are dominant to short plants, cross a heterozygous tall plant with a short plant.
what are the % phenotypes in the offspring of this cross?
tall=75%, short=25%
short=100%
tall=50%, short=50%
tall=100%
question 20
1 pts
one of the parents of a child has phenylketonuria (pku), which is caused by recessive alleles. the other parent does not have the pku alleles. what is the chance that the couple will have a child with phenylketonuria?
0
50
75
100

Explanation:

First Question (Plant Cross)

Step1: Define Genotypes

Let \( T \) = dominant (tall), \( t \) = recessive (short). Heterozygous tall: \( Tt \); short plant: \( tt \).

Step2: Set Up Punnett Square

	\( T \)	\( t \)
\( t \)	\( Tt \)	\( tt \)

Step3: Analyze Phenotypes

\( Tt \) = tall, \( tt \) = short. 2/4 (50%) tall, 2/4 (50%) short.

Step1: Define Genotypes

PKU is recessive (\( pp \)). Parent with PKU: \( pp \); Parent without PKU alleles: \( PP \).

Step2: Cross Genotypes

\( PP \times pp \) → All offspring: \( Pp \) (no PKU, since dominant \( P \) is present).

Step3: Determine Probability

No offspring will have \( pp \) (PKU), so chance is 0.

Answer:

Tall=50%, short=50%

Second Question (PKU Inheritance)