Detection of Mutations in Drosophila: CLB and Attached Methods

Detection of Mutations in Drosophila: CLB and Attached Methods

Drosophila melanogaster (fruit fly) is a widely used model organism for studying genetic mutations due to its simple genetic structure and short life cycle. Two primary methods used for mutation detection in Drosophila are the CLB method and the attached-X method.

1. CLB Method

The CLB (C = Crossover suppressor, L = Lethal, B = Bar-eye) method is used for detecting mutations on the X chromosome in male flies.

• Principle:

  1. This method relies on a balancer chromosome that suppresses crossing over and carries lethal mutations and a phenotypic marker (e.g., Bar-eye).
  2. The lethal mutation prevents homozygous offspring, allowing the detection of mutations in heterozygotes.

• Procedure:

  1. A male fly with a normal X chromosome is crossed with females carrying the CLB chromosome.
  2. The offspring inherit either the normal X chromosome or the CLB chromosome.
  3. Male offspring that survive must carry the normal X chromosome.
  4. The appearance of phenotypic abnormalities in males is indicative of mutations on the inherited X chromosome.

• Significance:

• Effective for isolating and identifying recessive lethal and visible mutations on the X chromosome.

2. Attached-X Method

The attached-X method is used to detect sex-linked mutations in Drosophila.

• Principle:

  1. In this method, females possess two X chromosomes fused at one end (attached-X), which are inherited together.
  2. Mutations on the male X chromosome can be identified by observing the phenotype of the progeny.

• Procedure:

  1. Cross males with a normal X chromosome to attached-X females.
  2. Male progeny receive their X chromosome from the father and the Y chromosome from the mother.
  3. Phenotypic analysis of male offspring reveals any mutations present on the paternal X chromosome.

• Advantages:

  1. Ensures all daughters inherit two X chromosomes, preventing lethal outcomes.
  2. Allows for straightforward detection of recessive mutations in males.

Applications in Mutation Studies

1. Both methods are instrumental in studying sex-linked genetic disorders, mutagenesis, and gene function in Drosophila.
2. They provide a robust platform for genetic mapping and mutation frequency estimation.