Intron and Exons Essay

1000 WordsApr 17, 20134 Pages
Why does DNA have introns and exons and what is the function of junk DNA? DNA, or deoxyribonucleic acid, is the hereditary material in humans and almost all other organisms. Nearly every cell in a person’s body has the same DNA. Most DNA is located in the cell nucleus (where it is called nuclear DNA). An important property of DNA is that it can replicate, or make copies of itself. Each strand of DNA in the double helix can serve as a pattern for duplicating the sequence of bases. This is critical when cells divide because each new cell needs to have an exact copy of the DNA present in the old cell. Before 1977, the mRNA molecules that transport information from DNA to ribosomes (the parts of cells that make proteins) were believed to be copies of the DNA, with each mRNA molecule aligning exactly with the stretch of DNA that coded for it. Then, in 1977, US biologist Phillip Sharp and British biologist Richard Roberts both discovered that genes are often separated or split by stretches of DNA that don't do anything. They called the active parts exons and the inactive parts introns. Before genes get to work, the cell makes a copy with the introns chopped out. Exons and introns refer to specific nucleotide base sequences in the genetic code that are involved in producing proteins. Exons are the DNA bases that are transcribed into mRNA and eventually code for amino acids in the proteins. Introns are DNA bases, which are found between exons, but are not transcribed. Genes which contain introns are known as interrupted genes. The discovery of introns and exons occurred independently in 1977 by American molecular biologists Richard Roberts and Phillip Sharp. Before this, it was said that eukaryote genes were strange as they contained more DNA than was copied into RNA. The two scientists ran experiments which attempted to identify DNA from the resulting mRNA. It was

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