STANDARD 16_ HEREDITY & REPRODUCTION
SC.912.L.16.9 Universality of the Genetic Code
SC.912.L.16.9 Universality of the Genetic Code
- Explain how and why the genetic code is universal and is common to almost all organisms
The Genetic Code is nearly Universal
- The genetic code is the language organisms use to convert instructions in the DNA into proteins. Scientists call it the Central Dogma of molecular Biology.
- The central dogma of molecular biology describes the two-step process, transcription and translation, by which the information in genes flows into proteins: DNA → RNA → protein. Transcription is the synthesis of an RNA from a segment of DNA. Translation is the process by which mRNA is used to make a polypeptide using the genetic code.
- The genetic code is a triplet code. DNA has 4 nucleotides bases (A, T, C, G) and RNA also uses 4 bases (A,U,C,G); the bases combine in groups of 3 forming a codon. Each of the codons in all organisms code for a specific amino acid, except for the stop codons, which only signal the end of translation.
- Recall that mitochondria and chloroplasts have their own DNA, and make their own proteins? They were considered to be independent organisms very long time ago before they became engulfed by another cell, beginning a symbiotic relationship that has persisted over time (Endosymbiotic Theory). The genetic code is nearly universal, because there are few exceptions. In 1979 scientists found that chloroplasts and mammalian mitochondria differ from the universal code. Few codons of their codons don't code for the same amino acids than in the rest of the organisms.
- The genetic code provides a strong evidence that all living things share a common ancestor
- Genetic engineering has also proved that the genetic code is universal. Scientist are able to insert genes from one organism into another. and produce the same proteins. For instance, inserting human insulin in a bacterium, which then expresses the gene by producing human insulin.
Why can bacteria recognize a human gene and then produce a human protein?
- A. DNA replication in bacterial and humans is the same.
- B. Bacterial cells contain the same organelles as human cells.
- C. The basic components of DNA are the same in humans and bacteria.
- D. Bacterial cells and human cells contain the same kind of chromosomes.