Question

100 300 400 200 A>G 800 500 AGGUA 600 exon 1 Hexon 2 exon 3 700 exon 4 CAG UGA AUG UAA AAAAA Lane: 1 2 3 Lane: 1 2 3 4 5 4 5 approx. size (bp) -900 approx. size (Da) -12,000 -11,000 -800 -700 - 10,000 -600 -9000 -500 -8000 -7000 -400 -300 -6000 Northern Blot Western Blot (fig56) At the top of the figure above is a gene diagram for a hypothetical gene, noting the length of each exon using the ruler at the top. Shown are the start and stop codons in exons 1 and 4, respectively, and also the polyadenylation signal sequence. Assume that polyadenylation will add a 200 nucleotide poly(A) tail onto the mRNA produced by this gene. Below the gene diagram are images of a northern blot and western blot. Assume that the samples in the same lane in both correspond with the same sample. For each scenario below, use the northern and western results to decide which lane best fits the scenario. An individual lane may match to more than one scenario, or none at all. For the western blot, assume a single amino acid has a mass of 120 daltons (Da). Normal splice variant, including all 4 exons [Choose ] [Choose none of these A cryptic U1 recognition site in intron 3 is lane 4 used instead of the normal site, incorporating lane 3 a premature UAA codon in frame lane 2 lane 1 lane 5 A mutation preventing use of the exon 2 [Choose] exonic splicing enhancers: AC>U RNA edit occurs at the CAG codon in exon 4 [Choose] An A>URNA edit occurs at the CAG codon in exon 4 [Choose]

Answer 1

1. None of these - Four lane for 4 exon are not in colinear order.

2. lane 3 - UAA genetic codon corresponding exon size is 500 bp and its corresponding Nothern blot is lane 3.

3. lane 5

4. lane 4

5. lane 2