Non-coding Regions of DNA
- DNA molecules are very long but only certain regions code for the production of polypeptides
- These are called coding sequences
- In humans only 1.5% of the genome contains coding sequences
- The majority of a eukaryotic genome contains non-coding regions of DNA that do not code for polypeptides but have other important functions
- Non-coding gene regulatory sequences are involved in the control of gene expression by enhancing or suppressing transcription
- Non-coding sequences can produce functional RNA molecules like transfer RNA (tRNA)
- Introns are non-coding sequences of DNA found within genes of eukaryotic organisms
- Different proteins can be produced from a gene depending on how introns are removed
- Telomeres are regions of repeated nucleotide sequences at the end of chromosomes that provide protection during cell division
- The repeated sequence facilitates binding of an RNA primer at the end of the chromosome leading to synthesis of an Okazaki fragment
- Without telomeres, DNA replication could not continue to the end of the DNA molecule and chromosomes would become shorter after every cell division
- Nonetheless, telomeres shorten with age due to oxidative damage within cells
- Loss of telomeres during ageing can be accelerated by smoking, exposure to pollution, obesity, stress and poor diet
- Antioxidants in the diet are claimed to reduce the rate of telomere shortening
The RNA molecule produced from the transcription of a gene contains introns that must be removed before translation can occur.
