1. Non-coding DNA makes up the majority of DNA in eukaryotic organisms but does not encode for proteins. It was once referred to as "junk DNA" but is now known to have important functions. 2. There are several types of non-coding DNA, including regulatory elements, introns, pseudogenes, repeats, transposons, telomeres, and various non-coding RNAs. 3. While the amount of non-coding DNA varies between species, it plays roles in chromosome structure, gene expression regulation, and protecting the genome from degradation.

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