Question

r = red flowers
r = white flowers
according to mendel’s law of dominance, which genotype(s) represent offspring with red flowers?
a rr
b rr
c rr or rr
d rr or rr

Explanation:

Step1: Recall Mendel's Law of Dominance

Mendel's Law of Dominance states that in a heterozygous condition, the dominant allele (here, \( R \) for red flowers) masks the effect of the recessive allele ( \( r \) for white flowers). So, genotypes with at least one \( R \) ( \( RR \) or \( Rr \)) will express the red flower phenotype.

Step2: Analyze the Punnett Square

The Punnett square has genotypes: \( RR \), \( Rr \), \( Rr \), \( rr \). Let's identify which genotypes give red flowers:

• \( RR \): Dominant homozygous, red.
• \( Rr \): Heterozygous, red (since \( R \) is dominant).
• \( rr \): Recessive homozygous, white.

So the genotypes for red flowers are \( RR \) or \( Rr \). Now check the options:

• Option A: \( RR \) (only one genotype, but \( Rr \) also gives red).
• Option B: \( Rr \) (only one genotype, \( RR \) also gives red).
• Option C: \( RR \) or \( Rr \) (matches the genotypes that produce red flowers).
• Option D: \( rr \) or \( Rr \) ( \( rr \) is white, so incorrect).

Answer:

C. \( RR \) or \( Rr \)