First cleavage reaction in nucleus leaves a 2-nucleotide overhang on the 3’ ends of the dsRNA product. This 3’ overhang is important for recognition of that RNA molecule by the next enzyme in the cytosolic pathway, Dicer.

TLS Online TPP Program

#Id: 3246

#Unit 3. Fundamental Processes

G modification. The figure shows specific sites on guanine that are vulnerable to damage by chemical treatment, such as alkylation or oxidation, and by radiation.

TLS Online TPP Program

#Id: 3247

#Unit 3. Fundamental Processes

Mutations are also caused by compounds that substitute for normal bases (base analogs) or slip between the bases (intercalating agents) to cause errors in replication. 

TLS Online TPP Program

#Id: 3248

#Unit 3. Fundamental Processes

One of the most mutagenic base analogs is 5-bromouracil, an analog of thymine.

TLS Online TPP Program

#Id: 3249

#Unit 3. Fundamental Processes

The presence of the bromo substituent allows the base to mispair with guanine via the enol tautomer

TLS Online TPP Program

#Id: 3251

#Unit 3. Fundamental Processes

5-bromouracil induces transitions in both directions, A:T ↔ G:C.

TLS Online TPP Program

#Id: 3254

#Unit 3. Fundamental Processes

Tautomeric forms of the four common bases in DNA.