Question

Name the enzymes responsible for transcription of tRNA and hnRNA from template DNA strands.

Answer 1

Transfer RNA or tRNA is a small RNA chain that transfers a specific amino acid to a growing polypeptide chain during translation. It has a site for amino acid attachment and a three-base region called the anticodon that recognizes the corresponding three-base codon region on mRNA via complementary base pairing. In eukaryotic cells, tRNA transcription is done by RNA polymerase III. RNA Pol III moves along the DNA and matches the DNA nucleotides with a complementary RNA nucleotide to create a new RNA molecule. The copying of the DNA continues until the RNA Pol III reaches a termination signal, which is a specific set of nucleotides that mark the end of the gene to be copied. The initial transcripts produced from tRNA genes are precursor molecules which are processed into mature tRNAs.

In eukaryotes, the primary transcript is much larger than the mature mRNA and is called Heterogeneous nuclear RNA (hnRNA). hnRNA undergoes processing and finally, the mRNA is produced so it is called mRNA precursor or pre mRNA. Synthesis of hnRNA is done by RNA polymerase 2 enzyme which reads the DNA sequence and adds the complementary nucleotides to create new RNA molecules.