Question

I am a beginner in experiment design so please correct me if I made any mistakes. If we want to study the behavioral changes after a particular mutation of a gene, it seems to be a must for all individuals to be genetically identical before we induce the mutation (otherwise those changes may not be caused by the mutation, but other genetic variants)

For example, if we are using fruit flies for genetic study, we need to enclose them (with food and air) such that they can only mate over many generations in that container.

Question: After many generations, supposedly a very large number offspring which has very similar genetic makeup can be generated ready for mutagenesis. However, may I ask how to test whether they are 100% genetically identical? I have thought of gene sequencing, but is highly impractical since there is a very large population involved.

Answer 1

Testing for 100% genetic identity in a large population is impractical. However, implementing rigorous breeding practices, such as sibling mating for several generations, can lead to a highly genetically homogeneous population, reducing the likelihood of significant genetic variation.

Step-by-step explanation:

To ensure genetic homogeneity, researchers often employ a technique known as sibling mating. By repeatedly mating siblings over several generations, the gene pool narrows, increasing the likelihood of genetic uniformity. Let's denote the initial generation as G0, and subsequent generations as G1, G2, and so forth. After multiple rounds of sibling mating, the majority of the population will share identical genetic material. However, achieving absolute genetic identity in a large population is practically impossible due to the potential for spontaneous mutations and genetic drift.

While sibling mating promotes genetic homogeneity, it does not guarantee 100% identity. Theoretically, after N generations of sibling mating (G_N), the relatedness coefficient (r) among individuals within the population increases. The relatedness coefficient quantifies the probability that two alleles at a given locus are identical by descent. Despite this increase in relatedness, small genetic variations may still persist.

Given these limitations, performing complete gene sequencing on the entire population becomes impractical due to the sheer size of the population. Instead, researchers often rely on statistical sampling and monitoring of specific genetic markers to assess the genetic homogeneity of the population. This strategy balances the need for practicality and the desire for a sufficiently homogeneous genetic background for subsequent mutagenesis studies.