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A unit of genetic length for DNA (or RNA) fragments equal to 1 million nucleotides (roughly equal to 1 cM).
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.


(meg′ă-bās″) [ mega- + base],


1. One million paired nucleotides in a DNA sequence.
2. One million unpaired nucleotides in a single-stranded nucleic acid sequence.
3. Informally, any very large fragment of DNA.
Medical Dictionary, © 2009 Farlex and Partners


A unit of measurement of the length of a segment of DNA equal to 1,000,000 base pairs. Usually contracted to Mb.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005

Megabase (Mb)

DNA or RNA of length 106 bases. Used as a unit of length for single-stranded or double-stranded molecules; although Mbp may also be used for the latter.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005
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Genome sequencing followed by wgMLST analysis revealed no nucleotide differences across 1.5 megabases of compared genome sequences between the 3 strains.
Genetic variation ranges from the single base pair (bp) to several megabases (Mb) compared to a reference genome [9].
We've used a 1 million base length in our examples above; in reality, usual read lengths range from a few hundred kilobase to the current published record of 2.2 megabases. With 1 Mb being a reasonable midpoint to these values, it's easy to see where this approach can both read through many repetitive regions at a single pass, and where much less bioinformatics work is needed in tiling than on short-read systems.
A 1/8 reauction scheme was selected on the basis of the estimated genome size of about 500 megabases (Mb).
A CGH-Array (3/3/10) with a resolution of 250 kilobases found the de novo 3q26.33q27.3 microdeletion, with a loss of approximately 7.6 megabases. Severe mental delay was determined in the child.
This model of limited specificity of TFs is supported by TF occupancy observed in a genome browser (ChIP seq) [35] at two different scales: at the small scale of a few kilobases TFs look to recognize specific regions (TF binding sites) of a promoter, but at a genome scale of megabases each TF is seemingly randomly distributed, and each random distribution of a TF is specific to each individual TF.
However, causal genes that are megabases away from GWAS-implicated lead SNPs have been identified in other settings (Musunuru et al.
Nowadays chromosomal microarray analysis give the opportunity to detect the aberrations limited to kilobases rather than megabases and also accompanying by important challenges the other advances molecular test like next-generation sequencing can offer more detailed prenatal analysis.
The main cause of the disease is attributed to mutations in one of the largest protein-coding genes in the human genome called dystrophin that spans 79 exons (2.2 megabases) and stabilizes muscle cells by anchoring the cytoskeleton to the extracellular matrix with other proteins, in a complex known as the dystrophin-associated glycoprotein complex (DAGC) [18].
These structural alterations can range from 1 kilobase to several megabases and include either a single gene or contiguous sets of genes.
Gene start point is shown on the chromosome, while gene sizes are shown in megabases (Mb) against each gene.
This discrepancy between a low percentage of visible ALK FISH-positive cancer cells and homogeneous ALK expression can be explained by the fact that EML4 is only 12 megabases apart from ALK.