Chromosome walking

Saakre ManjeshCPBMBKAU

Introduction

• Chromosome walking is a method of positional cloning used to find, isolate, and clone a particular allele in a gene library.

• Developed by Welcome Bender, Pierre Spierer, and David S. Hogness in the Early 1980's. 

KNOWN

Construction of library

1A DNA fragment from a chromosome contains and identify sequence (usually

a gene)

Fragment 2

2

Fragment 1

Fragment 3

Prepare restriction map

Use this sequence as probe

Probe produced by subcloning ; subclone -1

Hybridize with clones from genomic library

Isolate fragment-2 prepare restriction map of fragment-2

Successive fragments

12

3

1 2 3

Overlapping sequences

Use this sequence as probe

Probe produced by subcloning ; subclone -2

Hybridize with clones from genomic library

3

continue

Application

• The analysis of genetically transmitted diseases, to look for mutation

• Discovery of single-nucleotide polymorphism of different organisms.

• To know the unknown flanking region of the chromosome• Now a days it can be use for the metagenomics process to

know the genome sequence of the unknown organism

Disadvantages

• Speed of chromosome walking • Difficulty of walking through the repeated sequence that are

scattered through the gene.

• Chromosome walking could easily be stopped by un clonable sections of DNA.

• A solution to this problem was achieved with the advent of chromosome jumping (Marx, 1989), which allows the skipping of unclonable sections of DNA