How DNA Works section 2

Unraveling DNA DNA is often wound around proteins, coiled into strands and bundled up in prokaryotic cells- loose loop in eukaryotic cells - bundled into chromosomes

Allows it to hold information Structure of DNA Allows it to hold information The order of the bases on one side is the code for the information carried Genes- string of nucleotides that give a cell information on how to make a specific trait There is an enormous amount of DNA, so there is a variety of genes to hold it Human DNA contains 3 billion base pairs If you could print a book containing all the genetic information found in one cell, it would be 500,000 pages long ou

Genes and Proteins DNA code is read like a book one end to the other bases form an alphabet 3 bases = code for a specific amino acid CCA = proline AGC = serine long strings of amino acids make proteins so each gene is instruction to make a specific protein

Proteins and Traits proteins are found throughout the cell and cause most differences we see proteins act as chemical triggers and messengers for many processes with in the cell proteins help determine height, colors we see, curly or straight hair, etc proteins exist in an almost limitless variety thousands of genes = thousands of code for proteins

Help from RNA RNA = ribonucleic acid helps the proteins similar to DNA serves as a temporary copy of DNA several forms to help transform DNA into proteins tRNA - transfer RNA mRNA - messenger RNA

Making a protein copy one side of a DNA segment with RNA copy is called mRNA; it moves out of the nucleus into the cytoplasm mRNA is fed through the protein assembly line in the ribosomes mRNA is fed in 3 bases at a time tRNA translates the 3 bases of the mRNA tRNA matches an animo acid to the bases animo acids become linked in chain chain leaves the ribosome and folds into a new protein molecule

Changes in Genes Changes in the number, types or order of bases in a piece of DNA is a mutation 3 types of mutations deletion - base is left out insertion - base is added substitution - when the wrong base is used ( most common)

Do mutations matter? There are 3 possible consequences to changing DNA can improve a trait no change at all can create a harmful trait Cells can make proteins to detect and fix errors, but repairs are not accurate and become part of the genetic code If the mutation is in the sex cells, the change can be passed down to the next generation

How do mutations happen? Happens regularly because of errors when the DNA is copied Can happen when something abnormal happens to the cell Any physical or chemical agent that causes a mutation is called a mutagen Mutagens include high energy radiation- x-rays, UV rays asbestos chemical in cigarettes

An Example of a Substitution A mutation, like substitution, can be harmful because it can cause a gene to make the wrong protein example - GAA (glutamic acid) if copied as GTA ( valine acid) This change can cause sickle cell disease When valine is substituted for glutamic acid in the blood protein, the red blood cells are changed into a sickle shape sickle cells : not good oxygen carriers get stuck in blood vessels cause painful and dangerous blood clots

An Example of Substitution Chain of amino acids forming normal hemoglobin Normal red blood cell Mutated DNA Complementary copy Chain of amino acids forming mutated hemoglobin Sickled red blood cell

Uses of Genetic Knowledge Since Watson and Crick made their model, scientists have learned a lot about DNA used to benefit humans has also caused ethical and scientific debates

Scientists can manipulate individual genes within an organism Genetic engineering Scientists can manipulate individual genes within an organism called genetic engineering transfer genes from one organism to another ex. transfer biochemical from firefly to plant produced a glowing plant scientists may use genetic engineering to create new products drugs, food, fabrics bacteria producing proteins found in spider's silk cow proteins used to create human proteins produce proteins needed for a human with a genetic disease scientists also worry about creating genetically engineered organisms

(drag & drop into wells) Elapsed Time DNA Gel Electrophoresis DNA Gel Electrophoresis START Run 5 min 10 min 15 min 20 min 25 min 30 min 35 min 40 min 0 min 45 min Negative Ultraviolet wells: Kilobases 10.0 8.0 6.0 5.0 4.0 3.0 2.0 1.5 1.0 0.5 Positive Agarose Gel STOP A Samples C D 1kb Ladder B Infinite Cloner (drag & drop into wells)

Genetic Identification DNA is unique, like fingerprints DNA fingerprinting is used to identify patterns in a human's DNA DNA fingerprinting is used as evidence in criminal investigations Also can be used to help identify individuals like World Trade Center victims Can be used to show family relationships or hereditary diseases

Cloning A clone is a new organism that has an exact copy of another organisms genes this has done with small mammals cloning humans is being debated