Question

Explain the triplet code of DNA. Name the molecule that copies the triplet code of DNA. Name the organelle that is the site of protein synthesis. What other function does this organelle have in protein formation? (p. 59)

Short answer

Answer: mRNA, or messenger RNA, is responsible for copying the DNA triplet code during transcription, creating a complementary sequence of nucleotides that carries the genetic code needed for protein synthesis. This process occurs within the cell's organelle called the ribosome, which is found in the cytoplasm, and is responsible for reading the information in the mRNA and assembling the correct sequence of amino acids to create a protein.

Step-by-step solution

1. Explain the Triplet code of DNA

The triplet code of DNA refers to a set of three nucleotide bases, also known as a codon. Each codon in the DNA sequence corresponds to a specific amino acid, which will be used to create proteins. In other words, the DNA sequence is "read" as a series of three bases at a time, and each unique combination of bases codes for a specific amino acid in a protein chain. There are 64 possible codons, corresponding to 20 amino acids and three stop signals.

2. Name the molecule that copies the DNA triplet code

The molecule responsible for copying the DNA triplet code is the messenger RNA (mRNA). During transcription, the mRNA is synthesized using the DNA template, creating a complementary sequence of nucleotides. This process ensures that the information stored within the DNA molecule is accurately transferred to the mRNA, which then carries the genetic code to the organelle responsible for protein synthesis.

3. Name the organelle where protein synthesis occurs

Protein synthesis occurs in the organelle called the ribosome. Ribosomes are small, dense structures found in the cell's cytoplasm, either free-floating or attached to the endoplasmic reticulum. They are composed of two subunits, the large and the small subunit. Ribosomes are responsible for reading the information in the mRNA and assembling the correct sequence of amino acids to create a protein.

4. Explain the other function of this organelle in protein formation

In addition to protein synthesis, the ribosome has another essential function in protein formation: facilitating the process of folding the polypeptide chain into its correct three-dimensional structure. During translation, the ribosome moves along the mRNA, ensuring the correct anticodon on the transfer RNA (tRNA) pairs with the corresponding mRNA codon. As each amino acid is added to the growing polypeptide chain, the ribosome helps to fold the chain into its proper shape, which is essential for the protein's functionality. Once the protein is properly folded, it is often further processed and transported to its final destination within or outside of the cell.