Question

Sequence of nitrogen bases in coding strand of DNA was found to be CAT GTT TAT CGC. What would be sequence of nitrogen bases in mRNA synthesised over the corresponding region of template strand

• A. CAA GAA TAU GCC
• B. CAU GUU UAU CGC
• C. GTA CAA ATA GCC
• D. GUA CAA AUA GCC

Answer 1

The correct option is B CAU GUU UAU CGC

Nitrogen bases in DNA and RNA
1) The nitrogenous bases are of $2$ types - purines (adenine and guanine) and pyrimidines (cytosine, thymine and uracil).
2) RNA consists of adenine and guanine as purines.
3) RNA differs from DNA in terms of the pyrimidines that it possesses. It consists of cytosine and uracil in place of thymine. It does not contain thymine, unlike DNA.

Coding and non-coding strands of DNA
In DNA, the 5’-3’ strand is known as the coding strand. It is not used as a template for mRNA synthesis and is hence also known as the non-template strand.
The 3’-5’ strand is complementary to the coding strand and is used as a template for mRNA synthesis. It is known as the non-coding or template strand.

Sequence of template strand
The given sequence for a particular region of the coding strand is -
CAT GTT TAT CGC.
As the template strand is complementary to the coding strand, the sequence, the sequence of the template strand will be - GTA CAA ATA GCG.

Sequence of mRNA molecule
The sequence of the mRNA strand over the corresponding region of the template strand will be complementary to the sequence - GTA CAA ATA GCG.
As in the mRNA uracil will replace thymine, the sequence on the mRNA strand will be - CAU GUU UAU CGC

Final answer
(A) CAU GUU UAU CGC