Chromosome jumping
Chromosome jumping is a tool of molecular biology that is used in the physical
Chromosome jumping is used to bypass regions difficult to
Process
Chromosome jumping enables two ends of a DNA sequence to be cloned without the middle section. Genomic DNA may be partially digested using restriction endonuclease and with the aid of DNA ligase, the fragments are circularized at low concentration.
Library
Chromosome jumping library is different from chromosome walking due to the manipulations executed before the cloning step. In order to construct the library of chromosome jumping, individual clones originate from random points in the genome (general jumping libraries first basic protocol) or from the termini of specific restriction fragments (specific jumping libraries alternate protocol) should be identified. [1][4]
NotI-digested DNA
One example to build a library is a classified as a rare-cutting
Advantages and disadvantages
The advantages of chromosome jumping are:
- Allows more rapid movement through the chromosome walking.[1]
- Able to travel across chromosomal regions containing unclonable sequences in bacterial hosts.[1]
- Thirdly, this technique can be used to generate genomic markers with known chromosomal locations.[1]
- Combination of jumping and linking jumping libraries to walking offers possibility of directional walking and might allow the analysis of longer regions in parallel mapping strategies.[3]
- Reduces the complexity of libraries to be screened and constructed of mammalian genome.[3]
However, despite these advantages, chromosome jumping is still restricted by the capacity of the cloning vector which is the distance of the ends of the two fragments which can be approximately hundreds of kilobases.[2] Additionally, because the jump does not clone the intervening DNA, chromosome walking would have to be done to identify all the genes present in the DNA. [7] Regardless, it is still deemed to be beneficial due to the possibility to jump over hundred kilobases in comparison to chromosome walking.
Applications
Genetic disorders
Chromosome jumping libraries help address the complication of standard cloning techniques with large molecular distances. This process allowed the possibility to use the chromosome jumping library for other genetic disorders that requires 100 kilobases jumps.[4] Particularly for genetic disorders such as cystic fibrosis, its gene is located in human chromosome 7, was able to utilize the chromosome jumping library to search for a jumping clone, met oncogene. [4] Identification of the cystic fibrosis was complicated due to it existing in eukaryotic genes that is composed with coding (exons) and non-coding (introns) segments, where introns are small in size making them difficult for detection.[7] Another struggle in recognizing cystic fibrosis gene is because mammalian cells contains variety of repetitive DNA that can lead to incorrect cloning and blockage of DNA Replication and can cause instability.[8] Both these complications, traditional cloning techniques are unable to process because large yield of exons would have to be visible to produce a signal for the cystic fibrosis gene to be identified and DNA would have to be free of any repetitive elements. [7]
See also
- Shotgun sequencing
- Chromosome walking
- Chromosome landing
- Jumping library