Question

For the numbered steps below, select the option that places them in the correct order. 1) The ribosome binds to the mRNA and uses tRNAs to translate mRNA into the corresponding amino acid polypeptide sequence. 2) The spliceosome removes introns. 3) The primary structure of the polypeptide chain undergoes hierarchical foldings to form the tertiary structure. 4) RNA polymerase binds to the promoter region of a gene and initiates transcription.
(A) 1 > 2 > 3 > 4
(B) 3 > 1 > 4 > 2
(C) 2 > 1 > 4 > 3
(D) 4 > 2 > 1 > 3

Answer 1

Answer:

(D) 4>2>1>3

Explanation:

In order to answer the query, we need to understand the various steps of protein synthesis.

First of all, RNA polymerase binds to the promoter region of a gene on the DNA and initaties transcription. Transcription is the process by which we get mRNA (coding RNA) which is used as a template for protein synthesis.

After transcription, the resulting mRNA undergoes modification and maturation. This  involves removal of introns, addition of 3'-poly-A tail and 5'-cap. Introns are sequences that do not code for protein and are hence removed. The structure that removes introns is the spliceosome.

Then mature mRNA travels to the cytoplasm. Ribosome (composed of rRNA) binds to mRNA and tRNA to start the process of protein synthesis. The process of formation of protein is called translation.

During translation, the particular sequences on mRNA are read and corresponding tRNA with the relevant amino acid bind to the ribosome. The amino acids carried by various tRNAs are joined together to form the polypeptide (protein).

Finally, primary structure of protein may undergo folding to form a tertiary structure.

From the answer choices,

(D) 4 > 2 > 1 > 3

describes the process in correct order and is the correct answer choice.