Final answer:
The protein coded by the DNA strand TAC GCG ACT would start with methionine followed by arginine before reaching a stop codon, resulting in a dipeptide. Significant changes in function can result from alterations in the DNA sequence.
Step-by-step explanation:
The student is asking which protein is coded by the DNA strand TAC GCG ACT. To answer this, we must first transcribe the DNA sequence into an mRNA sequence and then translate it into an amino acid sequence. The DNA code word GCA corresponds to the amino acid arginine, and the DNA code word TCG corresponds to the amino acid serine. The transcription process involves replacing thymine (T) with uracil (U) when converting DNA to mRNA.
The mRNA sequence complementary to the given DNA strand TAC GCG ACT would be AUG CGC UGA. AUG is a start codon and encodes for the amino acid methionine; CGC encodes for arginine; and UGA is a stop codon. Therefore, the protein initiated by this sequence would begin with methionine, followed by arginine, and then it would stop translating due to the stop codon, resulting in a very short peptide of just two amino acids, Met-Arg, which is not a functional protein.
It is crucial to remember that a single nucleotide change in the DNA sequence can have significant impacts on the protein produced and its function, whether it results in a missense or nonsense mutation, potentially leading to diseases or malfunctioning proteins.