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. Begin by designing a genetic screen to identify recessive mutations. Use a mutagen, such as ethyl methanesulfonate (EMS), to induce random mutations in the germline cells of male Drosophila. These males will be the starting point for your screen.
2. Cross the mutagenized males with wild-type females to produce F1 progeny. The F1 generation will be heterozygous for any induced mutations, as the mutations are recessive and will not be phenotypically expressed in this generation.
3. To identify recessive mutations, intercross the F1 progeny to produce an F2 generation. In the F2 generation, approximately 25% of the offspring will be homozygous for any given recessive mutation, assuming Mendelian inheritance. These homozygous individuals will express the recessive phenotype, such as embryo lethality.
4. To propagate the recessive mutant alleles, maintain heterozygous carriers of the mutation. For example, you can cross heterozygous F1 individuals (mutant allele/wild-type allele) with each other or with a balancer stock. Balancer chromosomes are used to prevent recombination and maintain the mutant allele in the population.
5. Screen the F2 generation for embryo lethality by examining the offspring of heterozygous crosses. Embryos that fail to develop or hatch can be identified as homozygous for the lethal mutation. Maintain the stock by propagating heterozygous carriers to ensure the mutation is preserved for further study.

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, researchers typically perform controlled crosses between homozygous mutant flies and wild-type flies. The resulting offspring are then analyzed for the presence of the recessive phenotype, allowing for the establishment of stable lines of mutant alleles that can be further studied or utilized in experiments.