Chapter 15, Problem 21P

You have isolated another cDNA clone of the CRABS CLAW gene from a cDNA library constructed in the vector shown in Problem $20$. The cDNA was directionally cloned using the EcoR $\text{I}$ and Xho $\text{I}$ sites. You sequence the recombinant plasmid using primers complementary to the T $7$ and T $3$ promoter sites flanking the MCS (the positions of these sequences are shown in the figure in Problem $20$). The first $30$ to $\text{60}$ bases of sequence are usually discarded since they tend to contain errors.

Which of the sequence shown below represents the $5\prime$ end of the gene? Which sequence represents the $3\prime$ end of the gene?

Will the long stretch of T residues in the T $3$ sequence exist in the genomic sequence of the gene?

Can you identify which sequences are derived from the vector (specifically the MCS) and which sequences are derived from the cDNA clone?

Can you identify the start of the coding region in the $5\prime$ end of the gene? What does the sequence preceding the start codon represent?