NON CODING DNA (INTRONS) ALSO CALLED JUNK DNA. Non-coding DNA corresponds to the portions of an organism's genome that do not code for amino acids, the building blocks of proteins. Some non-coding DNA sequences are known to serve functional roles, such as in the regulation of gene expression, while other areas of non-coding DNA have no known function.Non-coding DNA is a type of DNA that does not code for proteins, but it could have functions related to the regulation of gene expression. The percentage of non-coding DNA content varies between species, but it's approximately 98% in humans. A significant portion of DNA was though to have no important biological function, and thus it was given the nickname "junk" DNA. A research study named "ENCODE," however, has revealed that around 80% of human junk DNA does seem to have relevant biochemical functions, due to its access to proteins such as transcription factors. Non-coding DNA can also code for RNA molecules such as microRNA (which is used to blocked translation), ribosomal RNA (which are used to build ribosomes), and transfer RNA (which is used in the process of translation. DNA that has previously been shown to have no biological function are still deemed important due to their high degree of homology and their conservation during evolution. Furthermore, some of the functions of non-coding DNA are yet to be fully understood. Non-Coding Regions of DNA Non-coding regions of DNA are defined as regions that do not directly contribute to protein synthesis. Non-coding regions can fall into the form of introns within genes, satellite DNA, telomeres, and regulatory sequences such as promoters. Non-coding DNA is a type of DNA that does not code for proteins, but it could have functions related to the regulation of gene expression. The percentage of non-coding DNA content varies between species, but it's approximately 98% in humans. A significant portion of DNA was though to have no important biological function, and thus it was given the nickname "junk" DNA. A research study named "ENCODE," however, has revealed that around 80% of human junk DNA does seem to have relevant biochemical functions, due to its access to proteins such as transcription factors. Non-coding DNA can also code for RNA molecules such as microRNA (which is used to blocked translation), ribosomal RNA (which are used to build ribosomes), and transfer RNA (which is used in the process of translation. DNA that has previously been shown to have no biological function are still deemed important due to their high degree of homology and their conservation during evolution. Furthermore, some of the functions of non-coding DNA are yet to be fully understood.

1. Faculty of Biosciences,
Institute of Biosciences and Technology,
Shri Ramswaroop Memorial University
By. Himanshu Verma
Roll No. 202110902120006
BSc. (H) Biotechnology
3rd Semester
Submitted To Dr. Nishu Mittal

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
 Pseddogenes
 Repeat sequences, transposons and viral elements
 Telomers

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 genome 5. Enhancers
2. Genetic switches 6. Silencers
3. Regulation of gene expression 7. Promoters
4. Trancription factor sites 8. Insulators

15. References
•https://en.wikipedia.org/wiki/Non-coding_DNA
•https://www.genome.gov/genetics-glossary/Non-Coding-DNA
•http://ib.bioninja.com.au/higher-level/topic-7-nucleic-acids/71-dna-
structure-and-replic/non-coding-dna.html
•https://www.sciencedirect.com/topics/biochemistry-genetics-and-
molecular-biology/noncoding-dna