Q17.3-1CC - Campbell Biology

Question

There are about 20,000 human protein-coding genes. How can human cells make 75,000-100,000 different proteins?

Step-by-Step Solution

Answer

Every gene present in the cell can produce different types of mRNA and, in turn, produce mRNA. It can lead to the formation of multiple proteins. 

Step 1: Definition of coding and non-coding genes

There are two types of regions present in a gene, known as a coding and non-coding gene. The coding genes are the genes that code for a particular protein. The non-coding genes are the genes that do not code for a protein.

In a whole DNA segment, the coding regions are limited compared to the non-coding region. Humans possess 20,000 coding genes.

Step 2: Explanation of protein synthesis

The translation is the process of protein synthesis. The proteins are decoded from the nucleotides from the mRNA to create a protein. There are many proteins formed from the mRNA. 

In human cells, more than 75,000 to 1 lakh proteins are produced.

Step 3: Reason for the formation of different types of proteins

Exons are the coding region present in the mRNA sequences. Alternative splicing is the mechanism that incorporates or removes the non-coding region to produce different types of several proteins. It is the process that can increase the diversity of protein in a living organism. 

It is the reason that several proteins are produced from a limited number of coding genes. The alternative splicing can produce multiple mRNAs from which different types of proteins are made.

Hence, the alternative splicing of the coding region is the reason for the formation of 75,000-100,000 different proteins from 20,000 human protein-coding genes.