How does dna encode information

The genetic code is degenerate as there are 64 possible nucleotide triplets 4 3 , which is far more than the number of amino acids.

These nucleotide triplets are called codons; they instruct the addition of a specific amino acid to a polypeptide chain. Sixty-one of the codons encode twenty different amino acids. Most of these amino acids can be encoded by more than one codon.

Three of the 64 codons terminate protein synthesis and release the polypeptide from the translation machinery.

These triplets are called stop codons. The stop codon UGA is sometimes used to encode a 21st amino acid called selenocysteine Sec , but only if the mRNA additionally contains a specific sequence of nucleotides called a selenocysteine insertion sequence SECIS. The stop codon UAG is sometimes used by a few species of microorganisms to encode a 22nd amino acid called pyrrolysine Pyl.

The codon AUG, also has a special function. In addition to specifying the amino acid methionine, it also serves as the start codon to initiate translation. The reading frame for translation is set by the AUG start codon. The genetic code is universal. With a few exceptions, virtually all species use the same genetic code for protein synthesis. The universal nature of the genetic code is powerful evidence that all of life on Earth shares a common origin.

Codons and the universal genetic code. Ribosomes are able to read the genetic information inscribed on a strand of messenger RNA and use this information to string amino acids together into a protein. It states that genes specify the sequence of mRNA molecules, which in turn specify the sequence of proteins. The translation of this information to a protein is more complex because three mRNA nucleotides correspond to one amino acid in the polypeptide sequence.

Transcription is the first step in gene expression. The ribosome travels down the mRNA, reading the codons and linking the appropriate amino acids together into a chain. A complete protein has hundreds of amino acids in its chain and may have more than one chain. Once assembly is complete, the ribosome falls off of the mRNA message and the completed chain of amino acids folds up into its functional protein structure.

The protein is now able to perform its job in the plant. A molecule called a ribosome is present in the cytoplasm and reads the RNA strand three nucleotides at a time. Each group of three nucleotides codon codes for a specific amino acid.

As the ribosome reads the RNA strand it places the proper amino acids together in the order encoded in the strand. Once all of the amino acids have been linked together, the protein folds up into the shape dictated by the order of the amino acids. This shape gives the protein its function and allows it to do its work in the cell. Genes Encode Proteins The information for making a specific protein is encoded in a single gene.

Proteins Proteins are chains of amino acids. Previous Page Next Page. The DNA segments that carry genetic information are called genes, but other DNA sequences have structural purposes, or are involved in regulating the expression of genetic information.

In eukaryotes such as animals and plants, DNA is stored inside the cell nucleus, while in prokaryotes such as bacteria and archaea, the DNA is in the cell's cytoplasm. Other proteins such as histones are involved in the packaging of DNA or repairing the damage to DNA that causes mutations.

DNA is a long polymer of simple units called nucleotides, which are held together by a backbone made of sugars and phosphate groups. This backbone carries four types of molecules called bases and it is the sequence of these four bases that encodes information. The major function of DNA is to encode the sequence of amino acid residues in proteins, using the genetic code.

These RNA copies can then used to direct protein synthesis, but they can also be used directly as parts of ribosomes or spliceosomes. Reference Terms. All known cellular life and some viruses contain DNA.