Question

In relation to gene organization and structure, explain the difference between single genes, gene families and tandemly repeated genes

Answer 1

DNA was 1st identified as an acidic substance present in the nucleus by Freidrich Meischer in 1869. It serves as the genetic material in all living organisms. Based on the X ray diffraction data produced by Rsoalind Franklin, Maurice Wilkins et. al., the model showing the structure of DNA was given by Watson & Crick This classic series of 3 papers was published in nature in 25th April, 1953.

The sequence of DNA comprises a gene and is packed in the form of chromosomes.

Genes are sequences of DNA coding for a functional protein or RNA. It comprises a promoter, operator, structural gene, terminator, regulatory sequences.

A gene family represents a set of similar genes in an organism which are homologous. These are formed by duplication of the original gene. The members of a gene family can either be present together or interspersed throughout the genome.

eg: globin gene family

Gene clusters are a part of gene family containing 2 or more genes involved in same or similar function present close to each other. These clusters can be tandemly repeated.

eg: Histone gene family (histone genes comprise a gene cluster and are present in tandem repeats. Each repeat consists of a copy of each of the 5 histone gene. These lack introns)

Tandem repeats are sequences of DNA repeated several times and present adjacently.

In short, a gene family involves a duplication of a whole gene while tandem repeats generally refer to short sequences repeated number of times.