Question

Refer to the given figure and consider the following statements regarding it.

I. A is present at the 5' end of the template strand.
II. B is antisense strand having 3' $\to$ 5' polarity
III. C may have AT rich region or palindromic sequences
IV. D acts as a non-template strand
Select the option with the incorrect pair of statements.

• A. I and IV
• B. II and III
• C. I and III
• D. III and IV

Answer 1

Answer: (C)

Transcription is the process of synthesizing mRNA from DNA sequence. The region of DNA that undergoes transcription is flanked is given the term transcription which includes a promoter region, terminator region and the structural gene.
The sequence of DNA undergoing transcription is the structural gene section which is used as template to make the copy of mRNA. This process is catalysed by DNA dependent RNA polymerase that catalyzes the reaction in $5’\to 3’$ direction only. Thus, the template sequence is in opposite polarity (3' $\to$ 5') as mRNA is complementary to it. The non-template strand of DNA is generally called as sense strand as it follows the same sequence as that of mRNA. Hence, template strand is also called anti-sense strand.
The structural gene sequence is flanked by two sequential region -
Promotor region found on the 3' end of template strand and helps in binding of RNA polymerase thus promoting transcription.
Terminator region is found on the opposite end of promoter on the 5' end of the template strand and it regulates the end of the transcription process. This region is composed of a palindromic sequence that forms a stem-loop that is rich in G-C base pairs followed by several T bases.