Question

The following cross can never result in a recessive phenotype?

• A. Tt Pp \(\times\) Tt Pp
• B. TT Pp \(\times\) tt pp
• C. tt pp \(\times\) TT PP
• D. tt pp \(\times\) Tt Pp

Hint:

Crossing \[ \boxed{ ttpp \times TTPP } \] always gives \[ \boxed{ 100\%\,TtPp, } \] so no recessive phenotype appears.

Answer 1

The Correct Option is C

Step 1: Recall the condition for a recessive phenotype. A recessive phenotype appears only when the genotype is homozygous recessive. For two genes, \[ \boxed{ttpp} \] is the recessive phenotype.

Step 2: Check each cross. For option (A), \[ TtPp \times TtPp \] can produce \[ ttpp, \] so a recessive phenotype is possible. For option (B), \[ TTPp \times ttpp \] all offspring are \[ TtPp \text{ or } Ttpp, \] so recessive phenotype for both genes is not produced, but recessive phenotype for one gene is possible. For option (C), \[ ttpp \times TTPP \] produces only \[ TtPp. \] Every offspring is heterozygous for both genes. Hence, \[ \boxed{ttpp} \] can never be produced. For option (D), \[ ttpp \times TtPp \] may produce \[ ttpp. \] Therefore, \[ \boxed{ttpp \times TTPP} \] can never result in a recessive phenotype. Thus, \[ \boxed{(C)} \] is the correct answer.