Question

In detail, describe and/or illustrate each of the chemical processes whereby genetic information is transferred from nuclear genes in a eukaryotic cell to the final usable protein.

Answer 1

Genetic information is flow from nucleic acid to protein, which are stored in genes. Genes are made up of DNA (consist of two long polynucleotide chains composed of four types of nucleoside subunits: adenosine, guanosine, thymine and cytosine). Two chains are held together by hydrogen bonds between bases on complementary strand. This information is transcribed onto RNA and from RNA translated into sequence of amino acids or polypeptides. And then polypeptide undergoes post-translational modification to become a functional protein. The detail process of transfer of Genetic information from nuclear genes to the final usable protein is described in following steps:

1. Transcription (DNA?RNA)

  

It is the first step in gene expression. In transcription a RNA copy of a gene's DNA sequence is transcribed. The RNA copy carries the information needed to build a polypeptide. There are three stages in transcription: initiation, elongation, and termination.

1. Initiation. RNA polymerase binds to the promoter, a sequence of DNA.

2. Elongation. The template strand, acts as a template for RNA polymerase.

3. Termination. Terminators signal that the RNA transcript is complete.

The RNA molecules processed after transcription get spliced and have a 5' cap and poly-A tail on their ends.

This produces messenger RNA having the information in nucleotide sequence and can be used to synthesize protein.

2. Translation (RNA?protein)

mRNA carries the instructions for building a polypeptide and read in groups of three nucleotides (As, Us, Cs, and Gs) called codons. Transfer RNAs are molecular "bridges" that connect mRNA codons to the amino acids they encode. One end of each tRNA has an anticodon, which can bind to specific mRNA codons. The other end of the tRNA carries the amino acid specified by the codons.

Ribosomes are the structures where polypeptides (proteins) are built, where all process of translation launches.

Translation further divided into three stages: initiation , elongation and termination .

3. Protein further goes into post translational modification.