Methods of Post-Transcriptional Regulation

POST TRANSCRIPTIONAL REGULATION OF GENE EXPRESSION,
Method 1: Alternative splicing


Alternative splicing can produce different forms of a protein from the same gene.



RNA splicing has to do with shortening transcripts of many eukaryotic genes by removing introns from
the pre-mRNA.



1.) In the first step, the pre-mRNA is cut at the 5' splice site (the junction of the 5' exon and the
intron).



2.) The 5' end of the intron (U1 snRNP) then is joined to the branch point (U2snRNP) within the
intron. This generates the loop-shaped mRNA molecule characteristic of the splicing process.



3.) Adenine in branch point “attacks” 5’ site (U1 snRNP)  lariat formation (loop-like formation)
and free 3’OH.



Drosophila sex determination

In humans’ sex depends on an X or Y chromosomes. In flies sex determination depends on ratio of
autosomes to sex chromosome.

Ratios that determine males, females, super males, and super females

1 X chromosomes: 2 autosome -> male

1 X chromosome: 1autosome -> female

<1 X chromosome: 2 autosome -> super male

<1 X x chromosome: 1 chromosome -> super female

There are 3 genes involved in drosophila sex determination

1.) Sex-lethal(sxl) -> this is a splicing repressor