Difference Between Coding and Non-Coding DNA

The difference between Coding & Non-Coding is that Coding DNA has a sequence to encode proteins whereas noncoding DNA does not have a sequence to encode for proteins. Coding and noncoding DNA are two components of an organism’s DNA or genome. A genome of an organism is the complete set of DNA including all of its genes in a cell. 

• The genome is represented by the whole set of chromosomes in the nucleus.
• A DNA molecule consists of specific nucleotide sequences. 
• A small proportion of the DNA sequences contain genetic information for protein synthesis. This is called coding DNA. 
• A larger proportion of the DNA sequences contain genetic information for regulation and proportion only. This is called noncoding DNA. 
• In other words, the DNA sequences that encode proteins are known as coding DNA and the sequences that do not encode proteins are known as noncoding DNA. 
• In the human genome, only about 1.5 % is coding DNA and nearly 98 % is noncoding DNA.

Key Terms: DNA, RNA, mRNA, tRNA, rRNA, codons, coding DNA, Noncoding DNA, transcription, translation, exons, introns

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Coding DNA

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The DNA which has genes that encode for a protein is called coding DNA. The coding region of a DNA has the nucleotide sequence that codes for proteins. The coding regions can transcribe, translate and produce proteins. 

• Proteins have structural, functional as well and regulatory importance in all cells. 
• The percentage of coding DNA is always less than the noncoding DNA.
• The protein-encoded sequences of coding DNA will be transcribed to mRNA (messenger RNA). 
• The mRNA will be translated into amino acid sequences on ribosomes. 
• The sequence of amino acids makes specific proteins.

pre-mRNA

The coding region of DNA consists of sequences known as exons. Exons gene portions that have the genetic code for the production of specific proteins. In humans, only about 1.5 % of the entire genome length corresponds to coding DNA. The coding DNA has more than 27000 genes.

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Transcription and Translation

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Transcription is a process of conversion of a segment of DNA into RNA. The resulting RNA molecules can encode several proteins. These RNAs are called mRNAs. 

• The process of the genetic information of mRNA into proteins is called translation.
• The process of transformation usually occurs outside the nucleus in the cytoplasm.

Transcription & Translation

Read More: RNA Interference

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Noncoding DNA

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The DNA that does not code for any protein is called a noncoding DNA. Noncoding DNA undergoes transcription to form noncoding RNA. 

• The noncoding RNAs are rRNA (ribosomal RNA) and tRNA (transfer RNA).
• Noncoding RNAs also regulate the protein-coding sequences or protein synthesis.
• The quantity of noncoding DNA availability is a species-specific trait.
• The major part of the genome consists of noncoding DNA. It accounts for more than 98% of the genome.

Non-coding DNA

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Exons and Introns

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Exons are the coding sequences in mRNA that code for the amino acid sequence of the protein. Exons are retained in mature mRNA after post-transcriptional modification.

• These are highly conserved sequences and so they do not frequently change with time.
• Introns are intervening sequences between two exons found in eukaryotic DNA sequences. 
• Introns do not directly code for proteins. Introns undergo the process of splicing, otherwise an incorrect sequence will be formed. 
• They are removed before the formation of proteins from mRNA. 
• They are the non-coding parts of the nucleotides and are not highly conserved.

Read More: Bioinformatics

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Difference between Coding and Noncoding DNA

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The difference between Coding & Non-Coding is mentioned in a tabular form:

Also Read:

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Things to Remember

• Coding DNA has a sequence to encode for proteins, whereas noncoding DNA does not have a sequence to encode for proteins.
• Coding DNA is transcribed into mRNA, but noncoding DNA is transcribed into tRNA and rRNA.
• The coding DNA has exons and the noncoding DNA has regulatory elements, introns, repeating sequences, pseudogenes, and telomeres.
• In Eukaryotes coding DNAs are approximately 1.5% of the total genome
• Whereas in Prokaryotes coding DNAs are approximately 80% of the total genome.
• In Eukaryotes noncoding DNAs form around 98.5% of the genome, whereas in prokaryotes, noncoding DNAs form around 20% of the genome.
• Coding DNAs encode proteins that have regulatory, structural, as well as functional importance, whereas noncoding DNAs control and regulate gene activity

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