Noncoding DNA

Noncoding DNA refers to components of an organism's DNA sequences that do not encode protein sequences. Some noncoding DNA is transcribed into functional non-coding RNA molecules (e.g., transfer RNA, ribosomal RNA, and regulatory RNAs), while others serve as structural and regulatory sequences, or have no currently known function.

Overview

Noncoding DNA sequences make up a significant portion of many genomes. For instance, over 98% of the human genome is composed of noncoding DNA. While the functions of noncoding DNA are still a subject of ongoing research, these sequences are known to play key roles in the regulation of gene expression, chromosome structure, and DNA replication.

Types of Noncoding DNA

Noncoding DNA can be classified into several types, including:

• Introns: These are noncoding sections of a gene that are transcribed into the precursor mRNA molecule, but are removed by RNA splicing during the generation of the mature mRNA.
• Intergenic regions: These are regions of DNA located between genes. They can contain regulatory DNA sequences, transposons, and sequences that have no currently known function.
• Regulatory sequences: These sequences control the transcription and translation of nearby genes. They include promoters, enhancers, silencers, and insulators.
• Structural DNA: This includes centromeres and telomeres, which play key roles in chromosome structure and function.
• Repetitive DNA: This includes satellite DNA, minisatellites, microsatellites, and transposable elements.

Function

While the function of many noncoding DNA sequences is still unknown, it is clear that these sequences play a critical role in the biology of organisms. For instance, regulatory sequences control the timing, location, and level of gene expression, while structural DNA sequences are essential for chromosome stability and replication.

See also

• Junk DNA
• Gene expression
• Genome
• DNA replication
• RNA splicing

References

Noncoding DNA Resources
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