Question

1. Using the following terms, describe the process of transcription a. Template strand, non-template/coding strand, DNA, RNA, RNA polymerase, 3 5, 5 3', uracil, promoter, termination sequence, enhancer, nucleus, cytoplasm. What process often follows transcription? How is the genetic code used in this process ?

Answer 1

Ans.1) Transcription is process of processing of RNA from DNA molecule. Two strands of DNA has opposite polarity one with polarity 3' $\rightarrow$5' (also known as template strand) as RNA polymerase can polymerise ribopolynocleotide only in direction 5'$\rightarrow$3'.

Enhancer sequences are short sequences present over DNA but plays very vital role in increasing the transcription of genes present over that DNA. Enhancers are bounded by activator proteins.

RNA polymerase binds to promoter site over template strand and synthesizes a RNA transcript with complimentary nucleotides, only difference in nucleotides over RNA and DNA is presence of Uracil as complimentary nucleotide to adenine in place of thymine.

RNA polymerase keeps on adding new ribonucleotides (polymerising) until it encouters termination sequence. Termination sequnces acts as signal to stop transcription.

The complete process of synthesis and processing of RNA occurs in nucleus and after mature RNA is formed, it is translocated to cytoplasm to another process to be followed i.e translation of this RNA to protein. Proteins perform several functions inside the cell.

Transcription is followed by process of translation i.e protein synthesis.

Genetic code is present over mRNA which is coded by DNA molecule, genetic code is present in form of triplets of nuleotides. This triplet is called codons. Each codon codes for a particular amino acid. Series of codons present over mRNA helps in synthesizing a polypeptide sequence. Trancription involves ribosomes, tRNA, free amino acids and many other cytosolic factors.