human genome contains approximately three billion base pairs of DNA. Within this, there are between 30,000 and 70,000 genes, which together add up to less than 5 percent of the entire genome. Most of the rest is made up of several types of noncoding repeatitive elements.The relative percentage of non repetitive DNAin bacteria is 100% and decreases in the higher developed eucaryotes,70% in Drosophila and 55% in animals and 33% in plants. Most gene sequences are unique, found only once in the genome. In contrast, repetitive DNA elements are found in multiple copies, in some cases thousands of copies, unlike genes, most eukaryotic genomes that have been analyzed. What functions they serve, if any, are mainly unknown. Their presence and spread causes several inherited diseases, and they have been linked to major events in evolution.
Repeated sequences (repetitive elements) are patterns of nucleic acids (DNA or RNA) that occur in multiple copies throughout the genome. Repetitive DNA was first detected because of its rapid reassociation kinetics. In many organisms, a significant fraction of the genomic DNA is highly repetitive, with over two-thirds of the sequence consisting of repetitive elements in human. …show more content…
satellites,minisatellites, and microsatellites largely exist in the form of tandem arrays (these elements originally got their name as "satellites" because they separated from the bulk of nuclear DNA during centrifugation). Sequences repeated in tandem are common at the centromere (where the two halves of a replicated chromosome are held together), and at or near the telomeres (the chromosome tips). Because they are difficult to sequence, sequences repeated in tandem at centromeres and telomeres are underrepresented in the draft sequence of the human genome. This makes it difficult to estimate the copy number, but they certainly represent at least 10 percent of the
Repeated sequences (repetitive elements) are patterns of nucleic acids (DNA or RNA) that occur in multiple copies throughout the genome. Repetitive DNA was first detected because of its rapid reassociation kinetics. In many organisms, a significant fraction of the genomic DNA is highly repetitive, with over two-thirds of the sequence consisting of repetitive elements in human. …show more content…
satellites,minisatellites, and microsatellites largely exist in the form of tandem arrays (these elements originally got their name as "satellites" because they separated from the bulk of nuclear DNA during centrifugation). Sequences repeated in tandem are common at the centromere (where the two halves of a replicated chromosome are held together), and at or near the telomeres (the chromosome tips). Because they are difficult to sequence, sequences repeated in tandem at centromeres and telomeres are underrepresented in the draft sequence of the human genome. This makes it difficult to estimate the copy number, but they certainly represent at least 10 percent of the