What effect will there be on RNA if the T in GAT is replaced by C?

The corresponding RNA would have "CUG" in place of "CUA"

Explanation:

The nucleotide sequence of the DNA template strand determines the sequence of RNA and the nucleotide sequence of mRNA specifies the amino acid sequence of the protein. Guanine in DNA template pairs with cytosine, adenine with uracil and thymine with adenine base in the RNA.

A DNA template strand with sequence "GAT" would specify the sequence "CUA" in the corresponding DNA. If "T" in the sequence of template strand is replaced with "C", then the corresponding RNA would have sequence "CUG".

However, amino acid leucine has a total of six codons: UUA, UUG, CUU, CUC, CUA, and CUG. Therefore, both the mRNA would code for the same amino acid.