The sequence of nitrogen bases of the template strand of DNA in a transcription unit is 3'-ATTGAACTG-5'. The sequence of nitrogen bases in its mRNA transcript would be:

5'-UAACUUGAC-3'

The correct answer is Option (2)- 5'-UAACUUGAC-3'

Transcription: Transcription is the process of copying a DNA sequence into an RNA molecule. During this process, RNA polymerase uses the DNA template strand to build a complementary RNA molecule.

Base Pairing: RNA polymerase follows the rule of complementary base pairing:

Adenine (A) pairs with Uracil (U) in RNA.

Guanine (G) pairs with Cytosine (C).

Thymine (T) in DNA is replaced by Uracil (U) in RNA.

Following these rules:

The template strand has 3'-ATTGAACTG-5' sequence. The complementary RNA molecule (mRNA transcript) will have: Uracil (U) instead of Thymine (T). The sequence will be read in the 5' to 3' direction for RNA. Therefore, the mRNA transcript sequence will be: 5'-UAACUUGAC-3'.