Non-coding regions of nuclear DNA
Much of the DNA in a eukaryotic nucleus does not code for polypeptides. These parts of the genome are described as non-coding DNA.
Some non-coding regions lie between genes and contain repeated copies of the same base sequence. Non-coding sequences can also form part of genes themselves.
- Multiple repeats are repeated base sequences found between genes.
- Introns are non-coding sequences located within genes.
- Introns occur between the coding regions known as exons.
Between genes
Non-coding DNA may contain stretches in which a particular base sequence occurs repeatedly.
Within genes
Non-coding introns can interrupt the coding sequences, or exons, within a gene.
Exam Tip: When giving examples of non-coding nuclear DNA, distinguish between repeated sequences between genes and introns within genes.