Question

What is the mechanism(s) that allows Drosophila P male and female strains to crossbreed and have fertile offspring?

1) Direct methylation of the P element in both P strains by DNMT1 inactivates P element.
2) Innate immunity mechanism based on epigenetic silencing of P element transposition, and differential splicing of the transposase mRNA.
3) Transposase mRNA is intact only in the somatic tissue and not in the germline; hence, gonads are not impaired.
4) There is a special protein, which binds to the 3rd intron in transposase mRNA and prevents its splicing out in germline resulting in an inactive transposase enzyme.

Answer 1

The crossing of Drosophila P male and female strains resulting in fertile offspring is facilitated by epigenetic silencing and differential splicing mechanisms which regulate transposase activity of the P element.

Step-by-step explanation:

The fertility of offspring from crossing Drosophila P male and female strains involves various mechanisms that regulate the activity of the P element, which is a transposon. The P element's ability to transpose is controlled to prevent genetic instability in offspring. One key mechanism involves epigenetic silencing, where mechanisms such as DNA methylation and RNA interference (siRNAs) target and inactivate the P element to prevent transposition.

The specificity of this process allows Drosophila P males and females to crossbreed and have fertile offspring by maintaining genome integrity. Mechanisms include the differential splicing of transposase mRNA in the sex determination pathway, which is intricately connected to the functioning and regulation of the P element. Females have two X chromosomes with genes like Sxl and tra that are spliced differently from males. This splicing determines the production of proteins that are essential for sex-specific development and function. Similarly, epigenetic mechanisms ensure that males, with only one X chromosome, have sufficient gene expression and prevent harmful overexpression in females.

Therefore, it is not just one but a complex interplay of mechanisms that ensures that when P male and female strains crossbreed, the transposase of the P element is rightly regulated, allowing for fertile progeny without genetic complications arising from transposition.