Question

Which of the following statements is TRUE regarding transcription in most organisms?

1. The RNA template strand is used to encode single-stranded RNA

2. All genes are transcribed from the same strand of DNA

3. Both DNA strands are used to transcribe from different strands of RNA

4. Different genes may be transcribed from different strands of DNA

5. The DNA template is used to encode single-stranded RNA

Answer 1

Correct statements are:

4. Different genes may be transcribed from different strands DNA

5. The DNA template is used to encode single stranded RNA

Discussion and explanation :

Process of RNA synthesis from DNA is termed as transcription. As we know DNA is a double stranded structure which forms a single stranded RNA after transcription with the help of RNA polymerase enzyme. For this only one strand of DNA acts as template for the single stranded RNA because if both strands are transcribed at same time, then both strands will be complementary to each other and bind thus inhibiting the goal of protein synthesis. Additionally both RNA molecules will produce two polypeptide which will differ in amino acid sequences.

At a time, only a part of DNA (gene) on single template strand termed as transcription unit is transcribed to produce mRNA coding for particular required polypeptide only. Transcription unit contains gene flanked by promoter and terminator.

Hence, false statements are :

1) RNA template strand is used to encode single stranded RNA ( actually DNA template strand is used to encode single stranded RNA)

2) All genes are transcribed from the same DNA strand (actually both strands have different genes which are transcribed separately as per requirement of the cell)

3) Both DNA strands are used to transcribe from different strands of RNA (Actually, one template strand is used for transcription into single strand of RNA or both DNA strands are used to transcribe for different strands of RNA).