Question

Mutations in the promoter can affect termination of transcription.

T or F

2.

Primase has 3' to 5' exonuclease activity

T or F

3.

Always termination of transcription requires the transcription of the terminator sequence.

True

False

4.

Why do longer double-stranded molecules of DNA melt at higher temperatures than longer double-stranded molecules of DNA?

		Because longer double-stranded molecules of DNA have more covalent bonds than shorter double-stranded molecules of DNA
		Because longer double-stranded molecules of DNA have more hydrogen bonds than shorter double-stranded molecules of DNA

Answer 1

1.

Promoter helps in the binding of transcription factors and initiation of transcription at the appropriate sites of DNA. Mutation in the promoter region causes transcription inhibition. Transcription termination has to occur only after initiation. As initiation do not occur, termination will also not occur.

It is appropriate to state that mutation in promoter region causes transcription inhibition.

So, the statement is false.

2.

RNA primase catalyzes the synthesis of RNA primers, so that the growing chain continues on RNA primer. This is vital in initiation of replication. Later, the RNA primers are removed by 5’to 3’ exonuclease activity.

However, primase do not have exonuclease activity.

So, the statement is false.

3.

The termination sequence acts as signal for termination of transcription. After the transcription of the termination sequence, which is highly specific, there occurs a loop formation due to the ‘U’ and GC-rich region on the transcribed sequence.

For termination to occur, the termination sequence gets transcribed.

So, the statement is true.

4.

The melting temperature of DNA (T_m) depends on length and specific nucleotides of a DNA molecule. With increase in length, the hydrogen-bonds in the molecule increase, causing it difficult to melt the DNA.

Thus, longer ds DNA molecules melt at a higher temperature than shorter ds DNA molecules, due the high number of hydrogen bonds in the longer strand.