Author Question: What sequence of bases on the second strand of DNA is complementary to the following? (5') ... (Read 133 times)

ss2343 · **on:** Aug 23, 2018

What sequence of bases on the second strand of DNA is complementary to the following?

(5') GCATTA (3')

Question 2

In some instances, base pairs other than the familiar GC and AT matches can form. For these alternate pairs to form, one of the two bases must tautomerize. Based on this information, draw a CA pair and determine the number of hydrogen bonds that would stabilize the pair.

Question 3

Describe, in general terms, the steps involved in the automated synthesis of the DNA sequence GCT.

akudia · **Reply #1 on:** Aug 23, 2018

Answer to Question 1

(3') CGTAAT (5') or (5') TAATGC (3')

Answer to Question 2

Two hydrogen bonds can form in a CA pair.

Answer to Question 3

Step 1
Attachment of 5'-DMT-N-benzoyl-2'-deoxyaguanosine to the polymer support by a 3' ester linkage.
Step 2
Deprotection of the 5'-hydroxyl by cleavage of the DMT ether with dichloroacetic acid in CH₂CL₂.
Step 3
Phosphite formation between the free 5'-hydroxyl of the polymer-bound N-protected 2'-deoxyguanosine and the phosphoramidite protected 5'-DMT-2'-deoxycytidine in the presence of tetrazole followed by oxidation to the phosphate triester with I₂.
Step 4
Repeat step 2 to deprotect the 5'-hydroxyl of the polymer-GC.
Step 5
Repeat step 3 to form the phosphate triester between 5'-hydroxyl of 2'-deoxycytidine residue and phosphoramidite protected 5'-DMT-N-benzoyl-2'-deoxythymidine.
Step 6
Cleave all protecting groups from the heterocyclic bases from the phosphates, as well as cleave the ester bond holding the DNA to the silica by treatment with aqueous ammonia.