A CpG island consists of about ____ copies of the CG dinucleotides. A.) 1000 B.)
ID: 66486 • Letter: A
Question
A CpG island consists of about ____ copies of the CG dinucleotides.A.) 1000
B.) 10
C.) 3
D.) 10,000
The textbook says "70-80%" but I have no idea how that fits with these numbers given. Thanks. A CpG island consists of about ____ copies of the CG dinucleotides.
A.) 1000
B.) 10
C.) 3
D.) 10,000
The textbook says "70-80%" but I have no idea how that fits with these numbers given. Thanks.
A.) 1000
B.) 10
C.) 3
D.) 10,000
The textbook says "70-80%" but I have no idea how that fits with these numbers given. Thanks.
Explanation / Answer
CpG island
(= CG island)
Region of genomic DNA rich in the dinucleotide C-G. Methylation of the C in the dinucleotide is maintained through cell divisions, and profoundly affects the degree of transcription of the nearby genes, and is important in developmental regulation of gene expression.There are around 30,000 CpG islands in a typical mammalian genome, and these tend to be undermethylated and upstream of housekeeping genes.
Unmethylated CpGs are often grouped in clusters called CpG islands, which are present in the 5' regulatory regions of many genes.The CpG sites or CG sites are regions of DNA where a cytosine nucleotide occurs next to a guanine nucleotide in the linear sequence of bases along its length. "CpG" is shorthand for "—C—phosphate—G—", that is, cytosine and guanine separated by only one phosphate; phosphate links any two nucleosides together in DNA. The "CpG" notation is used to distinguish this linear sequence from the CG base-pairing of cytosine and guanine. The CpG notation can also be interpreted as the cytosine being 5 prime to the guanine base.CpG dinucleotides have long been observed to occur with a much lower frequency in the sequence of vertebrate genomes than would be expected due to random chance. For example, in the human genome, which has a 42% GC content, a pair of nucleotides consisting of cytosine followed by guanine would be expected to occur 0.21 * 0.21 = 4.41% of the time. The frequency of CpG dinucleotides in human genomes is 1% — less than one-quarter of the expected frequency.CpG islands (or CG islands) are regions with a high frequency of CpG sites, though objective definitions for CpG islands are limited. The usual formal definition of a CpG island is a region with at least 200 bp, and a GC percentage that is greater than 50 %, and with an observed-to-expected CpG ratio that is greater than 60 %.
CpG islands are characterized by CpG dinucleotide content of at least 60% of that which would be statistically expected (~4–6%), whereas the rest of the genome has much lower CpG frequency (~1%), a phenomenon called CG suppression.
with the given details if u calculate then the copies of CG dinucleotides would be close to 1000 i.e. option A.
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