Question

42. Which of the following is not a normal property of the eukaryotic mRNAs?
A. Most have a significant untranslated region that doesn't direct assembly of amino acids
B. They are processed from pre mRNAS to mRNAs in the nucleus and are exported through the nuclear pore complex
C. All of the answers are true
D. They are found in the cytoplasm
E. They are often being translated by more than one ribosome at a time in a structure known as polyribosome or polysome

Answer 1

Answer: ‘C’ all of the answers are true.

Explanation: All are the normal properties of the eukaryotic mRNAs

A. Most have a significant untranslated region that doesn't direct assembly of amino acids : Untranslated regions (UTR) are sequences of nucleotides which are present either on 5’ region of mRNA or 3’ region of mRNA. If it is on the 5’side, it is known as leader sequence and if on 3’side it is known as trailer sequence. These regions are not translated in a polypeptide (sequence of amino acids). The 5’UTR is functional in initiation of translation for recognition by the ribosome and 3’UTR is functional in termination of translation.

B. They are processed from pre mRNAS to mRNAs in the nucleus and are exported through the nuclear pore complex : eukaryotic pre-mRNAs has introns(non coding region) in between the exons (coding regions), removal of introns is a part of post transcriptional modification with the help of which pre-mRNA is converted into mature mRNA, this process takes place in the nucleus where the mRNA is synthesized with the help of spliceosomes. Once the mature mRNA is formed it is transported to the cytoplasm for the translation process which takes place on the ribosomes. The mature mRNA is transported through nuclear pore complex which are present in between the nuclear membrane for transport of material in and out of the nucleus.

D.   They are found in the cytoplasm: Though mRNA are synthesized in the nucleus, they need to be transferred to the cytoplasm where they attach on the ribosomes and serve as the transcript for the process of addition of amino acids in the process of translation

.
E. They are often being translated by more than one ribosome at a time in a structure known as polyribosome or polysome: polysomes consist of a mRNA molecule with multiple ribosomes bound to it. Because of the limited number of mRNA, more number of same polypeptides can be synthesized using a single mRNA molecule with the help of polysomes.