In a cross between two heterozygous tall plants (Tt x Tt), what is the probability of offspring being short (tt)?

In a cross between two heterozygous tall plants (Tt x Tt), what is the probability of offspring being short (tt)?

• A. 0%
• B. 50%
• C. 25%
• D. 75%

Answer: (C)

When a trait is recessive, the short phenotype only shows up if the organism inherits the recessive allele from both parents. In a cross where both parents are heterozygous (one dominant and one recessive allele each), each parent can pass either allele with equal chance. The four equally likely genotype combinations that can arise are those where the recessive allele is present in both gametes—only that specific combination yields short. Because that short outcome comes from both parents contributing the recessive allele, it occurs in the minority of possible offspring. The other combinations produce tall offspring because the dominant allele is present at least once. So, the correct choice reflects that short offspring are a smaller share of the results, while most offspring will be tall.

When a trait is recessive, the short phenotype only shows up if the organism inherits the recessive allele from both parents. In a cross where both parents are heterozygous (one dominant and one recessive allele each), each parent can pass either allele with equal chance. The four equally likely genotype combinations that can arise are those where the recessive allele is present in both gametes—only that specific combination yields short. Because that short outcome comes from both parents contributing the recessive allele, it occurs in the minority of possible offspring. The other combinations produce tall offspring because the dominant allele is present at least once. So, the correct choice reflects that short offspring are a smaller share of the results, while most offspring will be tall.