Genetic concept types of gene...........

Types of gene. Molecular biology concept of gene

1. Gene Concept Molecular Biology

2. In prokaryotes, the coding sequences of genes are continuous. i.e , uninterrupted with a very few exceptions. In addition, the genes are organized into groups, each such groups forms a single transcription unit. i.e , Operon INTRODUCTION

3. Generally, the different genes occur as discrete unit separate from each other , but some prokaryotic genes may be overlapping. Eukaryotic genes present some interesting organisations . Such as split genes, Overlapping genes , pseudogenes etc. ….

4. Genes with interrupted sequence of nucleotides are referred to as split genes. Usually a gene has a continuous sequence of nucleotides. In other words, there is no interruption in the nucleotides sequence of a gene. such nucleotide sequence codes for a particular single polypeptide chain. SPLIT GENES

5. In other words, there is no interruption in the nucleotides sequence of a gene. such nucleotide sequence codes for a particular single polypeptide chain. However, it was were observed that the sequence of nucleotides was not contains in case of some genes, the sequences of nucleotides were interrupted by intervening sequences. ….

6. Split genes were independently discovered by Richard J. Roberts and Philip A. Sharp in 1977,for which they shared the 1993 Nobel prize in Physiology or Medicine. The first observations of interrupted genes, i.e , genes in which there are noncoding intron sequences between the coding exon sequences ,were made in animal viruses in 1977. HISTORY

7. Split Genes have two types of sequences: 1 ) Normal sequences ( exons) 2 ) Interrupted sequence ( introns) TYPES OF SPLIT GENES

8. 1 ) Normal sequence : This represents the sequence of nucleotides which are included in the mRNA is translated from DNA of split gene. T hese sequences code for a particular polypeptides chain and are known as exons Normal Sequence

9. 2) The intervening or interrupted sequences of split gene are known as introns. These sequences do not code for any peptide chain. Moreover, interrupted sequences are not included into mRNA which is transcribed from DNA of split genes. Interrupted sequence

10. Each interrupted gene begins with an exon and ends with an exon. The exons occur in the same precise order in the mRNA in which they occur in the gene. The same interrupted gene organization is consistently presented in all the tissues of organisms. Features of S plit Genes

11. The significance of split organisation of eukaryotic genes is not clear. Introns may also provide for increased recombination rates between exons of a gene and thus may be of some significance in genetic variation. Introns are known to code for enzymes involved in the processing of hn RNA. ( heterogeneous RNA). Significance of Split Genes