How would you conduct a screen to identify recessive mutations in Drosophila that result in embryo lethality? How would you propagate the recessive mutant alleles?

Verified step by step guidance

1. Start by selecting a population of Drosophila that is heterozygous for various mutations. This can be achieved by treating flies with a mutagen to induce random mutations.
2. Cross these heterozygous flies with a balancer stock. Balancer chromosomes are used to maintain recessive lethal mutations in a heterozygous state because they suppress recombination and carry dominant markers.
3. Screen the offspring for the absence of homozygous mutants. Since the mutation is recessive and lethal, homozygous mutants will not survive, and you will observe a reduction in the expected number of offspring.
4. To propagate the recessive mutant alleles, maintain the mutation in a heterozygous state by continuously crossing heterozygous carriers with the balancer stock. This ensures that the mutation is preserved in the population without expressing the lethal phenotype.
5. Periodically test-cross the heterozygous carriers to confirm the presence of the recessive lethal mutation by checking for the expected Mendelian ratios in the offspring.

Key Concepts

Recessive Mutations

Recessive mutations are genetic alterations that only manifest their effects when an individual has two copies of the mutant allele, one inherited from each parent. In Drosophila, these mutations can lead to specific phenotypic traits, such as embryo lethality, which can be identified through careful breeding and observation of offspring.

Drosophila Genetics

Drosophila melanogaster, commonly known as the fruit fly, is a model organism in genetics due to its simple genome, short life cycle, and ease of manipulation. Researchers use Drosophila to study genetic mutations, inheritance patterns, and developmental processes, making it an ideal subject for screening recessive mutations that affect embryonic development.

Propagation of Mutant Alleles

To propagate recessive mutant alleles, one must perform controlled crosses between individuals carrying the mutant alleles. By mating heterozygous flies (carrying one mutant and one wild-type allele), researchers can produce offspring that segregate the alleles, allowing for the identification and maintenance of homozygous recessive mutants in subsequent generations.