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TYPES OF NON CODING SEQUENCES

  GENES  The gene is a nucleic acid sequence that is necessary for function of gene product.  Gene may be a protein coding gene whose transcribed RNA is translated into proteins or RNA only genes.  Protein coding genes may be solitary or families or tandem repeats NON –CODING SEQUENCE   The non coding sequence are genes that do not encode the protein.  The amount of non-coding sequence in DNA of organism varies among species.  Eg-Human genome -98% non-coding genes  Prokaryotes -10% non-coding genes  Types of Non coding sequences The non coding sequences can be in the form of following Introns  Anti leader and Anti trailer sequence Promoter sequence Enhancers Pseudogenes Gene fragments Telomeres Non-coding functional RNA Cis-Trans regulatory elements INTRONS  Introns are non-coding sequence that transcribed into RNA  But precursor mRNA removed by splicing during processing.  The eukaryotic genome has large amount of introns...
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TYPES OF NON CODING SEQUENCES

 





GENES 

  • The gene is a nucleic acid sequence that is necessary for function of gene product. 
  • Gene may be a protein coding gene whose transcribed RNA is translated into proteins or RNA only genes. 
  • Protein coding genes may be solitary or families or tandem repeats

NON –CODING SEQUENCE 

  • The non coding sequence are genes that do not encode the protein. 
  • The amount of non-coding sequence in DNA of organism varies among species. 
  • Eg-Human genome -98% non-coding genes 
  • Prokaryotes -10% non-coding genes 

Types of Non coding sequences

The non coding sequences can be in the form of following

  • Introns 
  • Anti leader and Anti trailer sequence

  • Promoter sequence
  • Enhancers
  • Pseudogenes
  • Gene fragments
  • Telomeres
  • Non-coding functional RNA
  • Cis-Trans regulatory elements

INTRONS 

  • Introns are non-coding sequence that transcribed into RNA 
  • But precursor mRNA removed by splicing during processing. 
  • The eukaryotic genome has large amount of introns 
Eg- Human genome has 98.5% introns. 

  • The length of introns varies from 10-10,000bp 
  • The genes located inside introns are intronic genes (or)nested genes.
Function of Introns 
  • Generally do not coding for  proteins 
  • Helps in intron alternate splicing 
  • Exon shifting 
  • Control gene expression


Anti leader and Anti trailer sequence

  • The 5’ end of anti leader and 3’ end of antitrailer sequence are transcribed into RNA but not translated into proteins.
  • The 5’ anti leader sequence of  DNA is region between transcription start site and initiation codon
  • The 3’ trailer sequence of DNA is region between termination codon at end of transcription unit.


Promoter sequence

  • The promoter is a region of DNA that facilate transcription of particular gene.
  • Transcription factor bind to its factor.
  • They located at upstream of gene they regulate.
  • Eg TATA Box (25-35 bases long )
  • UPE (Upstream Promoter Element)

ENHANCERS

  • It is short region of DNA play key role in regulating expression
  • They serves as binding site for specific regulatory protein.
  • They greatly increases the effectiveness of promoters
  • It may located in upstream (or)downstream(or)internal

PSEUDO GENES
They are defective copies of fundamental genes that lost their protein coding ability.
They are 2 types
1.NON-PROCESSED PSEUDOGENES
  • Genes that have acquired one or more inactivating mutation.
2.PROCESSED PSEUDOGENES
  • It has formed from mRNA that has converted to DNA by reverse transcriptase and then integrated into genome.
GENE FRAGMENTS

  • These are inactive genes that lack a part of parent gene either 5’ or3’ region.
  • This is caused due to deletion or recombination that split the genes.

TELOMERES
  • These are end region of chromosomes that protect chromosomal detoriation during replication

NON-CODING FUNCTIONAL RNA

  • They are functional RNA molecules that are not translated into proteins.
  • Eg-rRNA, microRNA, tRNAetc…

CIS-TRANS REGULATORY ELEMENTS
  • Cis regulatory elements are sequences that control transcription of a nearby gene
  • Trans regulatory elements are sequences that control transcription of distance gene



References
1. Lewin's Gene - by Jocelyn E. Krebs, Elliott S. Goldstein, and Stephen T. Kilpatrick










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