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DNA sequences are both necessary and sufficient to specify centromere identity and function in organisms with point centromeres. In budding yeasts, the centromere region is relatively small (about 125 bp DNA) and contains two highly conserved DNA sequences that serve as binding sites for essential kinetochore proteins.
Centromeric DNA consists of a number of repetitive DNA sequences that often take up a significant fraction of the genome because each centromere can be millions of base pairs in length. In humans, for example, the sequences of all 24 centromeres have been determined [ 29 ] and they account for about 6% of the genome.
However, due to a lack of full centromere assemblies, base-level understanding of satellite array variation and evolution has remained weak. [5] For example, minisatellite DNA is a short region (1-5 kb) of repeating elements with length >9 nucleotides. Whereas microsatellites in DNA sequences are considered to have a length of 1-8 nucleotides. [8]
Intergenic regions may contain a number of functional DNA sequences such as promoters and regulatory elements, enhancers, spacers, and (in eukaryotes) centromeres. [2] They may also contain origins of replication, scaffold attachment regions, and transposons and viruses.
Repeated sequences (also known as repetitive elements, repeating units or repeats) are short or long patterns that occur in multiple copies throughout the genome.In many organisms, a significant fraction of the genomic DNA is repetitive, with over two-thirds of the sequence consisting of repetitive elements in humans. [1]
Chromosome 6 spans nearly 171 million base pairs (the building material of DNA) and represents between 5.5 and 6% of the total DNA in cells. It contains the major histocompatibility complex , which contains over 100 genes related to the immune response , and plays a vital role in organ transplantation .
Additional analyses of DNA sequences flanking human minisatellites have also revealed an intense and highly localized meiotic crossover hotspot that is centered upstream of the unstable side of minisatellite arrays. Repeat turnover therefore appears to be controlled by recombinational activity in DNA that flanks the repeat array and results in ...
The DNA sequence of two sister chromatids is completely identical (apart from very rare DNA copying errors). Sister chromatid exchange (SCE) is the exchange of genetic information between two sister chromatids. SCEs can occur during mitosis or meiosis.