Question

define the term reading frame . explain the possible effect of a mutation on a reading frame

Answer 1

A reading frame is a specific way of grouping the coding sequence of DNA into three base pairs or codons at a time, starting from a specific nucleotide. When the cell reads the genetic code in a particular reading frame, it enables the synthesis of the corresponding amino acids to construct a protein. In essence, a reading frame is the order in which codons specific to the genetic code are read to create a specific amino acid sequence.

A mutation can cause a shift or alteration in the reading frame of a genetic sequence. The mutation can occur due to deletions or insertions of nucleotides, substitutions of one nucleotide with another, or frame-shift mutations. This change can potentially disrupt the normal process of protein synthesis, leading to the production of an incomplete or defective protein.

If the mutation occurs in a non-coding region of the DNA (non-coding mutations), it might not affect the amino acid sequence of the protein. However, if the mutation occurs in a coding region (coding mutations), it can have significant effects on the protein produced. For instance, a substitution mutation where one nucleotide is replaced with another nucleotide, can result in a change in the corresponding amino acid. A deletion or insertion mutation can alter the reading frame, shifting the position of the codons, and potentially resulting in a truncated non-functional protein. Frame-shift mutations can also result in an absence or alteration of the stop codon precursor, leading to an extended protein or truncated protein. Therefore, a mutation in the reading frame can disrupt protein synthesis, which can either have minor or major consequences, including genetic disorders and diseases.