Question

Predict the different effects that an SNP would have if it were located in an exon, an intron, or an intragenic region.

Answer 1

The single nucleotide difference between the DNAs of different individuals is called SNP (Single nucleotide polymorphism). Most commonly, these variations are found in the DNA between genes. Now let us see what happens if SNPs are placed in different locations-

exon- exons are the coding sequences in the DNA which code for certain RNA or a protein. If SNP is placed here it may play a more direct role in the gene’s function, whether it can alter a normal function of that protein formed in the body or the difference which may cause a development of a disease. If a SNP occurs within a gene, then the gene is described as having more than one allele. In these cases, SNPs may lead to variations in the amino acid sequence.

Intron- these are the non-coding sequences in the DNA which were initially thought as "junk DNA" but now it has been made clear that these sequences play a very important role in the regulation of gene expression. If SNPs occurs here then it may create problems in the regulation of gene expression especially if it occurs in the main domain of gene control. This may lead to uncontrolled gene expression.

In between the genes- again if these regions are important for gene regulation then this may affect the gene expression and it may be uncontrolled but if SNPs occur at certain regions that are not necessary for gene regulation then certainly the SNPs would produce a silent effect.