Question

Read the following passage:

Generally, in eukaryotic cells the average length of a transcription unit along a DNA molecule is about 8,000 nucleotides, so the RNA product of the transcription is also that long. But it only takes about 1200 nucleotides from the above RNA product to translate average sized polypeptide of 400 Amino acids.

1. Name this RNA product transcribed from the DNA that subsequently translates into a polypeptide of 400 amino acids. Mention the enzyme responsible for transcribing this type of RNA from the DNA.     [1]
2. Name and explain the process the RNA molecule transcribed from 8000 nucleotide long DNA undergoes to be able to translate a polypeptide of 400 amino acids.     [2]
3. Write the number of RNA polymerases involved in the transcription of DNA in a prokaryote and eukaryotes.     [1]
   OR
   Mention the difference in the site of transcription in a prokaryote and eukaryote cell.     [1]

Answer 1

1. Messenger RNA (mRNA) is the RNA product generated from the DNA that later transforms into a 400 amino acid polypeptide. RNA polymerase is the enzyme in charge of transcription of mRNA from DNA.
2. Translation is the process by which an mRNA molecule can translate a polypeptide containing 400 amino acids. Translation takes place in the cytoplasm of eukaryotic cells. During translation, ribosomes read the mRNA molecule and assemble amino acids into a polypeptide chain based on the codons (three-nucleotide sequences) on it. Transfer RNA (tRNA) molecules transport the amino acids to the ribosome, where they are incorporated into the developing polypeptide chain.
3. In prokaryotes, such as bacteria, DNA transcription is normally performed by a single kind of RNA polymerase. In contrast, eukaryotes contain many RNA polymers. In humans, for example, there are three varieties of RNA polymerases: RNA polymerase I, II, and III, each of which transcribes a different form of RNA molecule.
   OR
   In prokaryotic cells, transcription occurs in the cytoplasm since there is no distinct nucleus. The DNA is present in the cytoplasm and RNA polymerase binds directly to the DNA to initiate transcription. In contrast, in eukaryotic cells, transcription primarily occurs within the nucleus.