Question

what is operon? an ORF? a SNP? briefly describe ORF and SNP

Answer 1

Operon

An operon is a functional unit of transcription.

In detail, a set of genes get transcribed into mRNA under the control of a single promoter and operator. The DNA segment consisting of operator, regulators and structural genes are called operon. For example, a set of genes required for lactose metabolism in prokaryotes (LacZ, LacY and LacA that facilitates lactose transport and metabolism) get transcribed as a unit and is referred as lac operon.

ORF

ORF stands for Open Reading Frame

To have the better understanding of open reading frame, we should first clear the concept of reading frame.

Basically, a reading frame is a method of dividing the DNA sequence (nucleotide sequence) into all possible consecutive codons (triplet). A DNA sequence can be divided into three reading frames. See the fig below

DNA sequence:

ATGCATGCCTGCATGCT

Possible reading frames

Now coming to the open reading frames, the DNA sequence cannot be translated in all three possible reading frames. It could be translated in only one frame.

The reading frame that could be translated is called open reading frame. A continuous stretch of DNA starting from a start codon (AUG) and ends with a stop codon (UAA or UAG or UGA) constitutes the open reading frame.

SNP

SNP stands for single nucleotide polymorphisms

When a single nucleotide such A or T or G or C differs in a genome of a population of an individual is referred as single nucleotide polymorphism.

For example, let us see the nucleotide sequence of two individuals of a population. In the nucleotide of two different individual a single nucleotide variation (Highlighted in red) is shown. This kind of variation in a single nucleotide is referred as SNP.