Question

What is a gene and how does the enzyme that catalyzes transcription find the start of the gene?

What is the DNA chain/thread read in the transcript?

Do the eukaryotes also have only one enzyme that catalyzes the transcription of RNA?

How are the eukaryotic primary mRNA transcripts processed before they can be transported from the cell nucleus to the ribosomes in the cytosol?

Answer 1

A gene is the basic unit of heredity. Genes are made up of deoxyribonucleic acid (DNA). DNA in each cell are finally translated to produce proteins, following the central dogma of biology. DNA is first replicated to daughter DNA which are then trasncribed to form messenger RNA (mRNA) which is finally translated in the ribosome to form a polypeptide that undergoes several post-transaltional modifications to give rise to a functional protein.

DNA is first scanned for a promoter region which is usually upstream of the transcription start site (eg. the TATA box). Once a transcription factor binds to the promoter region. the DNA is held in place nad transcription occurs by the enzyme RNA polymerase. There are different types of RNA polymerase present that varies in function. In eukaryotes, the main enzyme responsible for synthesising mRNA is RNA polymerase II. The mRNA prodcued in eukaryotes undergo 3 main processes- capping of 5' end by guanine residues, tailing and polyadenylation which serve as signals for the mRNA to be translocated outside the nucleus into the cytosol snd ribosome for transaltion.