2. INTRODUCTION
Radiation hybrid mapping is a genetic technique used to create a detailed
map of a genome. It works by breaking chromosomes into small fragments
using ionizing radiation and then fusing them with cells from a different
organism. By analyzing the resulting hybrid cells, researchers can map the
location of genes on the chromosomes with high precision. This technique
is useful for mapping genes that are difficult to study by other methods and
has been used in the mapping of human and animal genomes, as well as
in plant genetics.
3. IMPORTANCE OF HYBRID MAPS IN GENETIC RESEARCH
1. Creating a high-resolution physical map of the genome: Radiation hybrid
mapping enables the construction of a detailed map of the genome, which can
help identify the location of specific genes and other genomic features.
2. Mapping genes in regions that are difficult to study: Some regions of the
genome are difficult to study using traditional genetic mapping techniques.
Radiation hybrid mapping allows researchers to map genes in these regions
with high precision.
3. Identifying disease-causing genes: Radiation hybrid mapping can be used to
identify the location of genes that are involved in inherited diseases. This
information can be used to develop diagnostic tests and therapies for these
diseases.
4. Comparative genomics: Radiation hybrid mapping can be used to compare the
genomes of different species, helping researchers understand how species
have evolved over time and how they are related to each other.
4. HOW IT WORKS?
1. Irradiation: Cells from one organism are irradiated with a high dose of ionizing radiation,
which breaks the chromosomes into small fragments. The irradiation process is carefully
controlled to ensure that most of the chromosomes are broken into small fragments, but
not completely destroyed.
2. Cell fusion: The irradiated cells are then fused with cells from a different organism that
have been treated with a chemical agent to prevent them from dividing. The resulting
hybrid cells contain a mixture of chromosomes from both organisms, some of which have
been broken and rescued by the intact chromosomes from the partner cell.
3. Selection: The hybrid cells are then selected based on their ability to grow and divide,
using a selective medium that allows only the hybrid cells to survive.
4. Mapping: By analyzing the patterns of inheritance of the rescued fragments in a large
number of hybrid cells, researchers can map the location of genes on the chromosomes
with high precision. The technique is particularly useful for mapping genes that are difficult
to study by other methods, such as those located in regions of the genome that are highly
repetitive or have a low recombination rate.
5. Verification: The results of radiation hybrid mapping are usually verified using other
techniques, such as fluorescent in situ hybridization (FISH) or sequencing, to confirm the
location of the mapped genes and to fill in any gaps in the map.
5.
6.
7. ADVANTAGES OF RADIATION HYBRID MAPPING
1. High resolution: Radiation hybrid mapping provides a high-resolution
physical map of the genome, enabling the precise localization of genes and
other genomic features.
2. Mapping genes in difficult regions: This technique allows for the mapping of
genes in regions of the genome that are difficult to study by other methods,
such as highly repetitive or low-recombination regions.
3. Comparative genomics: Radiation hybrid mapping can be used to compare
the genomes of different species, helping researchers understand how
species have evolved over time and how they are related to each other.
4. Speed: This technique can generate a map of the genome in a relatively
short time, compared to other mapping methods.
5. Versatility: Radiation hybrid mapping can be used for any organism, as long
as cell lines can be established.
8. LIMITATIONS OF RADIATION HYBRID MAPPING
1. Cost: This technique can be expensive due to the equipment needed to
perform irradiation and cell fusion.
2. Technical expertise: Radiation hybrid mapping requires specialized training
and expertise, and is not a technique that can be easily performed by
researchers without experience in genetics and molecular biology.
3. False positives: Due to the complexity of the technique, false positive results
can occur, leading to errors in the mapping.
4. Chromosome instability: Radiation-induced DNA damage can lead to
chromosomal instability, which can affect the accuracy of the mapping.
5. Incomplete genome coverage: While radiation hybrid mapping can generate
a high-resolution map of the genome, it does not provide complete coverage
of the genome and gaps in the map may occur.
