Alternative splicing is a common mechanism for eukaryotes to expand their repertoire of gene functions. At least one estimate indicates that approximately 50 percent of human genes use alternative splicing, and approximately 15 percent of disease-causing mutations involve aberrant alternative splicing. Different tissues show remarkably different frequencies of alternative splicing, with the brain accounting for approximately 18 percent of such events.
(1) Choose the definition of alternative splicing.

a) Alternative splicing occurs when the nucleotide sequence of a pre-mRNA is actually changed prior to translation.
b) Alternative splicing occurs when copies of cis-regulatory elements upregulate or downregulate transcription yielding various combinations of proteins.
c) Alternative splicing occurs when group 1 intron are self-excised from a pre-mRNA yielding various combinations of exons in the final mRNA products.
d) Alternative splicing occurs when copies of a pre-mRNA are spliced in more than one way, yielding various combinations of exons in the final mRNA products.
e) Alternative splicing occurs when pre-mRNA has several different reading frames specifying more than one polypeptide.
(2) What is the evolutionary advantage of strategy alternative splicing offers to organisms?

a) The evolutionary advantage is that an organism can remove an exon containing the mutation during alternative splicing.
b) The evolutionary advantage is that an organism can encode more proteins without an increase in gene number.
c) The evolutionary advantage is that an organism increases the number of mRNAs to encode various proteins.
d) The evolutionary advantage is that an organism can increase gene number to encode varieties of similar proteins.