Where is the start codon located?a. at the start (5′ end) of the mRNAb. in the DNA just upstream of where transcription startsc. at the downstream end of the 5′ untranslated region (UTR)d. at the upstream end of the 3′ untranslated region (UTR)

Verified step by step guidance

1. Understand that the start codon is a specific sequence of nucleotides in mRNA that signals the start of translation.
2. Recall that the start codon is typically AUG, which codes for the amino acid methionine.
3. Consider the structure of mRNA, which includes regions such as the 5′ untranslated region (UTR) and the coding sequence.
4. Identify that the start codon is located at the beginning of the coding sequence, which follows the 5′ UTR.
5. Conclude that the start codon is at the downstream end of the 5′ untranslated region (UTR), which corresponds to option c.

Key Concepts

Start Codon

The start codon is a specific sequence of nucleotides in mRNA that signals the beginning of translation. It is typically the codon AUG, which codes for the amino acid methionine. This codon is crucial for ribosomes to recognize where to begin synthesizing a protein.

mRNA Structure

Messenger RNA (mRNA) is a single-stranded molecule that carries genetic information from DNA to the ribosome, where proteins are synthesized. The 5' end of mRNA is capped, and it contains a 5' untranslated region (UTR) before the start codon, which plays a role in the regulation of translation.

Transcription and Translation

Transcription is the process by which DNA is copied into mRNA, while translation is the subsequent process where ribosomes read the mRNA to synthesize proteins. The start codon is essential in translation, as it marks the point where the ribosome begins to assemble amino acids into a polypeptide chain.