Intro to gene expression (central dogma) (article) | Khan Academy
6 days ago Most genes contain the information needed to make functional molecules called proteins. (A few genes produce other molecules that help the. How genes in DNA can provide instructions for proteins. For example, Mendel's flower color gene provides instructions for a protein that helps make colored These relationships between codons and amino acids are called the genetic. While your genetic makeup does indeed determine physical traits like eye color, hair color and so forth, your genes affect these traits indirectly.
The size of a protein is an important physical characteristic that provides useful information including changes in conformation, aggregation state and denaturation. Protein scientists often use particle size analysers in their studies to discuss protein size or molecular weight.
Archibald Garrod Archibald Garrod was one of the first scientists to propose that genes controlled the function of proteins. Inhe published his observations regarding patients whose urine turned black.Genes to Proteins
This condition known as alkaptonuria happens when there is a buildup of the chemical homogentisate, which causes the darkening of urine. In most situations, excess amounts of amino acid phenylalanine are metabolised by the body.
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This led Garrod to surmise that the enzyme responsible for its breakdown must be defective in these patients. In addition, since the black urine phenotype was passed from generation to generation in a regular pattern, Garrod reasoned that a gene had to be responsible for the production of the defective enzyme.
Regulatory regions of the gene also contribute to protein synthesis by determining when the gene will be switched on or off.
Sciencing Video Vault Proteins In active genes, genetic information determines which proteins are synthesized and when synthesis is turned on or off. These proteins fold into complicated three-dimensional structures, somewhat like molecular origami. Because each amino acid has specific chemical characteristics, the sequence of amino acids determine the structure and shape of a protein. For example, some amino acids attract water, and others are repelled by it.
Some amino acids can form weak bonds to each other, but others cannot.
Teaching Unit 1: The Relationship between Genes and Proteins
The helix-loop-helix motif is found in calcium binding proteins, and a variant of it is found in regulatory proteins that bind DNA. The zinc-binding motif, also found in DNA binding proteins, is termed the zinc finger, because of the way that the residues protrude outward, like a finger. Figure Secondary structure motifs. Determining protein sequence If we purify a particular protein, we find that we can specify a particular ratio of the various amino acids that make up that specific protein.
But the protein is not formed by a random hookup of fixed amounts of the various amino acids; each protein has a unique, characteristic sequence. For a small polypeptidethe amino acid sequence can be determined by clipping off one amino acid at a time and identifying it.
Frederick Sanger worked out a brilliant method for deducing the sequence of large polypeptides. There are several different proteolytic enzymes—enzymes that can break peptide bonds only between specific amino acids in proteins.
Proteolytic enzymes can break a large protein into a number of smaller fragments, which can then be separated according to their migration speeds in a solvent on chromatographic paper. Because different fragments will move at different speeds in various solvents, two-dimensional chromatography can be used to enhance the separation of the fragments Figure When the paper is stained, the polypeptides appear as spots in a characteristic chromatographic pattern called the fingerprint of the protein.
Each of the spots can be cut out, and the polypeptide fragments can be washed from the paper. Because each spot contains only small polypeptides, their amino acid sequences can be easily determined. Figure Two-dimensional chromatographic fingerprinting of a polypeptide fragment mixture.