Problem

Solutions For An Introduction to Genetic Analysis Chapter 8 Problem 7P

Step-by-Step Solution

Solution 1

The hnRNA (heteronuclear ribonucleic acid) or pre-mRNA (messenger ribonucleic acid) has two kinds of sequences, namely introns and exons. The coding sequences are called exons and non-coding sequences are called introns. The processing of hnRNA, results removal of all introns, it is also called splicing. After splicing the hnRNA will get converted into an mRNA and it has only exons.

Step #2 of 5

Types of splicing are as follows:

• Group I (self-splicing intron sequences)

• Group II (self-splicing intron sequences)

• Pre-mRNA splicing (Spliceosomal complex)

• tRNA splicing

Step #3 of 5

The Adjoined figure shows spliceosome assembly and function (Figure 8-16):

$C:\Users\rajesh.r\Desktop\Spliceosome assembly and function.jpg$

Pre-mRNA splicing (Spliceosomal complex) requires 5 types’ snRNPs (small nuclear ribonuclear proteins) to cleave introns and join exons. These snRNPs include U1, U2, U4, U5 and U6. The functions of these snRNPs are as follows:

Step #4 of 5

U1 and U2 arrange splice sites at any termination site of an intron in a line by making hydrogen bonds between exon and the intron. U4, U5 and U6 form a Spliceosomal complex, which catalyzes the removal of intron by S_N1 (nucleophilic substitution) reaction. Finally, removes the intron and join the two exons.

Step #5 of 5

The Adjoined figure shows molecular reactions catalyzed by U4, U5 and U6 in exons splicing (Figure 8-17):

$C:\Users\rajesh.r\Desktop\Reactions in exons splicing.jpg$