Question

in peas puppe flowers are dominant to whote flowers. a homozygous purple flower is crossed to a whitw flower. what proportion of their offspring should be predicted to be white

and where does alternative mRNA SPLICING occur?

Answer 1

When a homozygous purple flower is crossed to a white flower, with purple as dominant there is a 1/2 or 50% proportion of their offspring to be white, with respect to the Mendel's law of inheritance.

Alternative mRNA splicing:

Alternative mRNA Splicing is a regulated process during gene expression that results in a single gene coding for multiple proteins, it occurs on particular exons which has to be removed or spliced from the final, processed mRNA from that gene.

When the pre-mRNA has been transcribed from the DNA, it includes several introns and exons. The exons to be retained in the mRNA are determined during the splicing process. The regulation and selection of splice sites are done by trans-acting splicing activator and splicing repressor proteins as well as cis-acting elements within the pre-mRNA itself such as exonic splicing enhancers and exonic splicing silencers.

Splicing of mRNA is performed by an RNA and protein complex known as the spliceosome, containing snRNPs designated U1, U2, U4, U5, and U6 , U1 binds to the 5' GU and U2, with the assistance of the U2AF protein factors, binds to the branchpoint A within the branch site. The complex at this stage is known as the spliceosome A complex. Formation of the A complex is usually the key step in determining the ends of the intron to be spliced out, and defining the ends of the exon to be retained and it determines the position where alternative mRNA Splicing occurs.