Question

How is protein synthesis affected if the normal base sequence TTT in the DNA template strand is changed to TTC?

Short answer

The change from TTT to TTC does not affect protein synthesis because both sequences code for lysine.

Step-by-step solution

- Understand the DNA Template Strand

The DNA template strand provides the sequence that is transcribed into mRNA. The normal base sequence given is TTT.

- Transcribe the DNA to mRNA

Transcribe the normal DNA sequence TTT into its complementary mRNA sequence. For DNA, adenine (A) pairs with uracil (U) in RNA, and thymine (T) pairs with adenine (A). So, TTT transcribes to AAA in mRNA.

- Determine the Normal Amino Acid

Translate the mRNA sequence AAA using the genetic code. The codon AAA corresponds to the amino acid lysine.

- Introduce the Mutation

Change the DNA template strand sequence from TTT to TTC. Now, rewrite the mRNA sequence based on this mutation. TTC transcribes to AAG in mRNA.

- Determine the Mutated Amino Acid

Translate the new mRNA sequence AAG using the genetic code. The codon AAG also corresponds to the amino acid lysine.

- Compare the Amino Acids

Compare the amino acids encoded by the normal sequence (AAA) and the mutated sequence (AAG). Both sequences code for lysine.

- Conclude the Effect on Protein Synthesis

Since both the original and the mutated sequences code for the same amino acid (lysine), the change from TTT to TTC does not affect protein synthesis.

Key concepts

DNA Template Strand

The DNA template strand plays a crucial role in the process of protein synthesis. It serves as a guide or template for creating a complementary mRNA strand during transcription. For example, the normal base sequence provided in the exercise is TTT. This sequence is used as a framework to build the complementary RNA strand.

mRNA Transcription

Transcription is the process by which the information in a DNA sequence is copied into mRNA. During transcription, enzymes read the DNA template strand and synthesize a complementary mRNA strand. In the case of the DNA sequence TTT, it transcribes to AAA in mRNA because thymine (T) pairs with adenine (A), and adenine (A) pairs with uracil (U) in RNA.

Genetic Code

The genetic code consists of codons, which are three-nucleotide sequences in mRNA that correspond to specific amino acids. For instance, the codon AAA in mRNA translates to the amino acid lysine. This genetic code is universal and allows the mRNA sequence to be translated into a precise sequence of amino acids, forming proteins.

Amino Acid Translation

Translation is the process where the ribosome reads the mRNA sequence and synthesizes a protein. Each codon in the mRNA is matched with its specific amino acid using transfer RNA (tRNA). As an example, the codon AAA in mRNA translates to lysine, which is then added to the growing protein chain.

Sequence Mutation

A sequence mutation involves a change in the DNA sequence. In this exercise, the normal sequence TTT changes to TTC. This mutation results in a new mRNA sequence of AAG instead of AAA. Despite this change, both codons AAG and AAA encode for the same amino acid, lysine, hence it does not affect the resultant protein. This showcases a type of mutation known as a silent mutation, where the change does not affect the protein's function.