basic dna structure and the coding and non-coding dna in our body.

1. NON – CODING DNA
CHAITRALI .V. JADHAV
ROLL NO:- 07
PAPER - 4

2. Noncoding DNA in Eukaryotes : Introduction
Each cell in our bodies has about 6 feet of DNA stuffed into it.
-However, less than one inch is devoted to genes!
 Non-coding DNA describes components of an organism’s DNA sequences
that do not encode for protein sequences.
 In many eukaryotes, a large % of an organism’s total genome size is non-
coding DNA.
 Amount of non-coding DNA & the proportion of coding versus non-coding
DNA varies greatly between species.
 Much of this DNA has no known biological function & was referred to as
“Junk DNA”.

4. Utricularia Gibba has 3% of non-coding DNA,
which is low for flowering plants.

5. Types of non- coding DNA sequences
 Non- coding functional RNA
 Cis- and Trans- regulatory elements
 Introns
 Pseudogenes
 Repeat sequences, transposons and viral elements
 Telomeres

6. 1.Non- coding Functional RNA
The RNA molecules which are not translated into
proteins.
 For eg:- Ribosomal RNA, Transfer RNA & Micro
RNA

7. 2.Cis- and Trans- Regulatory Elements
 Those are sequences that control the transcription
of a nearby gene.
 Located within 5’ or 3’ untranslated regions or
within introns.
 trans-regulatory element control the transcription
of a distant gene.

8. 3. Introns
 They are non-coding sections of a gene.
 Transcribed in the precursor m-RNA sequence
but is ultimately removed by RNA splicing.
 Most of the introns appear to be mobile genetic
elements.

9. 4. Pseudogenes
 They are related to known genes, that have lost their
protein-coding ability or are otherwise no longer expressed
in the cell.
 Arise from retrotransposition or genomic duplication of
functional genes.
 Therefore become “Genomic Fossils” : non-functional.

10. 5.Repeat Sequences, Transposons & Viral Elements
 Transposons & Retrotransposons are mobile genetic element.
 Retrotransposons : LINEs, SINEs – account for large proportion of the genomic
sequences in many species.
 Over 8% of the human genome is made up of endogenous retrovirus
sequences as a part of over 42% fraction that is recognizably derived of
retrotransposons.
 Remaining 3% can be identified to be the remains of DNA transposons.

12. 6. Telomeres
 Telomeres are regions of repetitive DNA.
 Located at the end of a chromosome.
 They provide protection from chromosomal
deterioration during DNA replication.

14. FUNCTIONS OF NON-CODING DNA
They have strong biological functions : some regions that are highly conserved are
under evolutionary pressure & positive selection.
 Some specific sequences of non-coding DNA are essential for chromosome
structure, centromere function & homolog recognition in meiosis.
 From study over 300 prokaryotic & 30 eukaryotic genomes, eukaryotes appear to
require less amount of non-coding DNA.
 Apart from this : 1. protection of the genome 6. Enhancers
2. Genetic switches 7. Silencers
3. Regulation of gene expression 8. Promoters
4. Transcription factor sites 9. Insulators
5. Operators

15. USES OF NON-CODING GENE
 Non-coding DNA evolution
 Long range Correlations
 Foreinsic anthropology

16. REFERENCES
 www.Wikipedia.org
 www.google.com
 www.Princeton.edu
 T. A. Brown