Question

Zebrafish (Danio rerio) have over 26,000 protein coding genes but their genome is roughly 1.7 billion base pairs (Gbp) - half the size of the human genome. The average human has 20,000 or fewer protein coding genes. Explain which components of the human genome lead to its larger size. Additionally, explain the mechanism that the component(s) use to expand or grow bigger in the human genome.

Answer 1

Human genome has large number of introns that do not code for protein. And its vast majority makes it larger in size. For translation the genes are transcribed into mRNA which then gets spliced. In splicing the introns are getting removed and only exons gets translated into proteins. The protein that is required by the cell/organism is only transcribed and translated.

Prokaryotes don't have introns. It has been gained after prokaryote-eukaryote divergence. They play important role because alternative slicing is very important for diversity among protiens, producing multiple varients of proteins from a single gene.