Given that the enzymes that catalyze nitrogen fixation are inhibited by oxygen, what are two ʺstrategiesʺ that nitrogen-fixing prokaryotes might use to protect these enzymes from oxygen?

1.  couple them with photosystem II (the photosystem that splits water molecules)

2.  package them in membranes that are impermeable to all gases

3.  be obligate anaerobes

4.  be strict aerobes

5.  package these enzymes in specialized cells or compartments that inhibit oxygen entry

TLS Online TPP Program

#Question id: 34172

#Unit 3. Fundamental Processes

Frameshifts occur when an extra nucleotide is inserted or omitted. Which of sequence and property is most sensitive combination for the frameshift to occur

TLS Online TPP Program

#Question id: 34173

#Unit 3. Fundamental Processes

The 3’–5’ exonucleolytic activity is found in which subunit of bacterial DNA Polymerase III

TLS Online TPP Program

#Question id: 34174

#Unit 3. Fundamental Processes

Once bound to a primer:template junction, DNA polymerase interacts tightly with much of the double stranded portion of the DNA by

TLS Online TPP Program

#Question id: 34175

#Unit 3. Fundamental Processes

A. For processive DNA synthesis, proofreading occurs without releasing the DNA from the polymerase

B. When a mismatched base pair is present in the polymerase active site, the primer:template junction is destabilize

C. The DNA polymerase active site binds such a mismatched template poorly, but the exonuclease active site has a 10-fold higher affinity.

D. The incorrect nucleotide is removed by the 5’-3’-exonuclease nuclease activity

Choose true and false

TLS Online TPP Program

#Question id: 34176

#Unit 3. Fundamental Processes

A. The lagging strand must be synthesized in the form of Okazaki fragments. 

B. Both strands are synthesized discontinuously. 

C. Not all of the fragment population represents bona fide Okazaki fragments; some are pseudofragments

D. Primers start with the sequence pppAG positioned opposite the sequence 3’–GTC-5’ in the template

Choose true and false

TLS Online TPP Program

#Question id: 34177

#Unit 3. Fundamental Processes

Which of the following combination of the statements regarding polA mutants is correct

A. fail to join their Okazaki fragments 

B. fail to removes the RNA primer

C. fail to removes the mismatch errors

D. fail to synthesis Okazaki fragments