Question

1. tall plants are dominant to short plants. (t = tall; t = short)

what are the genotypes of each of the following:

a. a plant is homozygous for the tall plant size allele:

b. a plant is homozygous for the short plant size allele:

c. a plant is heterozygous for plant size:

1. yellow is recessive to green in seed color in pea plants. write both the genotypes and phenotypes of each of the following using the letter for the dominant trait.

	genotypes	phenotypes
heterozygous
homozygous recessive

1. what is the only circumstance where a recessive trait will be seen in the phenotype?

why?

1. wrinkled leaves (w) are dominant and smooth leaves (w) are recessive. in the case of a heterozygous plant (ww), why are the leaves not smooth?

Explanation:

Step1: Define homozygous dominant

Homozygous means two identical alleles; dominant is T.
Genotype: $TT$

Step2: Define homozygous recessive

Homozygous means two identical alleles; recessive is t.
Genotype: $tt$

Step3: Define heterozygous

Heterozygous means two different alleles (T and t).
Genotype: $Tt$

Step4: Assign dominant allele for seed color

Green is dominant, use $G$; yellow is recessive $g$.

Step5: Fill homozygous dominant row

Homozygous dominant = $GG$, phenotype = Green seeds

Step6: Fill heterozygous row

Heterozygous = $Gg$, phenotype = Green seeds

Step7: Fill homozygous recessive row

Homozygous recessive = $gg$, phenotype = Yellow seeds

Step8: Identify recessive phenotype condition

Recessive trait only shows with two recessive alleles.

Step9: Explain dominant allele expression

Dominant allele masks recessive in heterozygotes.

Answer:

Question 20:

a. $TT$
b. $tt$
c. $Tt$

Question 21:

	Genotypes	Phenotypes
Heterozygous	$Gg$	Green seeds
Homozygous Recessive	$gg$	Yellow seeds

Question 22:

A recessive trait will only be seen in the phenotype when an organism has two copies of the recessive allele (is homozygous recessive).
Why? Because a dominant allele will always mask the expression of a recessive allele; only when no dominant allele is present can the recessive trait be expressed.

Question 23:

The heterozygous plant ($Ww$) has a dominant allele ($W$) for wrinkled leaves. Dominant alleles mask the expression of recessive alleles ($w$) in the phenotype, so the dominant wrinkled leaf trait is expressed instead of the recessive smooth leaf trait.