Presentation on theme: "Genetics lecture #2 Gene Expression. GENE TO PROTEIN Genes hold the information for just about everything that happens in an organism. But information."— Presentation transcript:
Genetics lecture #2 Gene Expression
GENE TO PROTEIN Genes hold the information for just about everything that happens in an organism. But information alone doesn't do much. It would be like an architect with plans to build a structure. But the structure needs the construction workers in order to actually build something. And obviously, you need the bricks to build the house. In living things, those bricks are called AMINO ACIDS.
Gene to Protein cont. Genes basically have the instructions for putting amino acids (the bricks) together in a way that makes a structure that has a function. There is a repeating theme in biology: STRUCTURES HAVE A FUNCTION. A sweater has the function of keeping you warm. It can do this because of its structure. A sweater is made of yarn in a way that makes it retain heat to keep you warm. So if we think of that yarn being made of many small pieces, we can call those pieces AMINO ACIDS. And then we call the structure with a function (the sweater) a PROTEIN.
Gene to Protein cont.. Therefore, proteins are structures with functions. These functions can move bones (muscles) or change the rate of chemical reactions in an organism - ENZYMES. The meat of a steak is mainly protein just as chicken or pork meat. So to recap: Genes hold the information for putting together many amino acids to make proteins.
THE GENE TO PROTEIN PATHWAY If amino acids are the bricks for the house, then there are 20 kinds of bricks at the hardware store. Some are made at the store and some need to be shipped-in. The amino acids that need to be shipped-in are called the essential amino acids. Essential amino acids are the ones we need in our diet to be healthy. There are 20 amino acids with half (10) being essential, meaning we need to eat them. These 20 amino acids are put together in specific combinations to build structures that have a function (a protein).
PROBLEM? If genes (DNA) holds the information for putting amino acids together, how do we put together parts with 20 different names with only 4 words? The trick is that it takes 3 letters to specify one amino acid. This is called a TRIPLET CODE. Using this formula there are 64 possible names.....more than enough to specify the 20 amino acids that make proteins.
FLOW OF INFORMATION: THE ROLE OF RNA DNA is transcribed to Pre-messenger RNA (Pre-mRNA) Pre- mRNA is the same length of the DNA strand being copied. DNA has a lot of blank stretches that do not code for protein (INTRONS) strands that does code for proteins - expressed (EXONS) Like DNA, Pre-mRNA has both introns and exons. Before the mRNA can leave the nucleus to go to where proteins are made (ribosomes), it needs to be condensed by the pieces that are blank (introns) and pasting together the good pieces exons). Once the blanks have been removed, it is called mRNA. It is mRNA that takes the for putting together amino acids at ribosomes (the place where proteins are)
AT THE RIBOSOMES... A ribosome is made from ribosomal RNA (rRNA) and proteins. Once the mRNA arrives at the ribosome, a third kind of RNA comes into the picture. Transfer RNA (tRNA) is the taxi that picks-up lose amino acids and brings them to the ribosome to be put together into long chains (polypeptides) to make proteins. RECAP: DNA Pre-mRNA mRNA ribosomes + tRNA + amino acids = proteins!