Question

where do the instructions for building a protein originally come from?
○ dna
○ trna
○ mrna
○ rrna

Explanation:

To determine the origin of protein - building instructions, we analyze each option:

• DNA: It holds the genetic code. Genes (segments of DNA) have the information for making proteins. The process of transcription copies the DNA sequence into mRNA, but the original instructions are in DNA.
• tRNA: Its role is to transfer amino acids during translation, not to hold the original instructions for protein building.
• mRNA: It is a copy of the DNA sequence (made during transcription) and carries the instructions to the ribosome. However, it gets its information from DNA, so it's not the original source.
• rRNA: It is a component of ribosomes, which are the sites of translation. It doesn't carry the original instructions for protein building.

So, the instructions for building a protein originally come from DNA.

Answer:

A. DNA