1. You have been provided with seven partial DNA sequences which originated from

Question

1.       You have been provided with seven partial DNA sequences which originated from seven different organisms. Each of these sequences is from a gene that codes for a b-globin chain (an immune-protein) from these organisms. The dotted line marks the border between an intron and an exon. Using what you know about introns and exons, and taking an evolutionary perspective, can you determine which side of the dotted line would be the intron and which the exon? Please justify how you arrived at your answer.

GGTGGTGAGGCCCTGGGCAG .    GTAGGTATCCCACTTACAAG

GGTGGTGAGATTCTGGGCAG    . GTAGGTACTGGAAGCCGGGG

GGGGGCGAAGCCCTGGGCAG . GTAGGTCCAGCTTCGGCCAT

GGTGGTGAGGCCCTGGGCAG . GTAGGTATCAAGGTTACAAG

GGTGGTGAGGCCCTGGGCAG . GTAGGTATCCAGGTTACAAG

GGTGGTGAGGCCCTGGGCAG . GTAGGTATCCTTTTTACAGC

GGCCATGATGCCCTGACCAG    .    GTAACTTGAAGCACATTGCT

Explanation / Answer

The spliceosome recognizes AG-GT exon intron junction sequence.
Here, the AG sequence belongs to the exon and GT sequence belongs to an intron.
So, the left side sequences in the given image represent exons and the right side sequences represent introns (or next exons).

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