Gene expression and mutations are fundamental concepts in molecular biology that determine how genetic information is used and modified within cells.
Control of gene expression involves multiple regulatory mechanisms that determine when and how genes are activated or repressed. Transcription factors play a crucial role by binding to specific DNA sequences to either promote or inhibit gene expression. One important example is Oestrogen, which acts as a transcription factor in human cells by binding to specific response elements. Epigenetics represents another layer of control through chemical modifications like acetylation of histones, which can alter DNA accessibility without changing the genetic code itself.
DNA mutations can significantly impact protein structure and function through various mechanisms. Substitution mutations involve the replacement of one nucleotide with another, while insertion mutations and deletion mutations add or remove nucleotides respectively. These changes can lead to different outcomes: missense mutations alter the amino acid sequence, potentially affecting protein folding and function. Frameshift mutations occur when the number of inserted or deleted nucleotides isn't divisible by three, disrupting the entire reading frame. The consequences of mutations can be classified as either gain-of-function mutations, where proteins acquire new or enhanced activities, or loss-of-function mutations, where protein function is reduced or eliminated. Common examples in humans include sickle cell anemia (caused by a substitution mutation) and cystic fibrosis (often resulting from a deletion mutation). Understanding these concepts is crucial for medical research and genetic counseling, as mutations can lead to various genetic disorders and diseases. The impact of mutations on protein structure and function depends on factors such as the location of the mutation, the type of amino acid change, and the importance of the affected region for protein function.
