HOW DOES DNA WORK? Section 4.2

Vocabulary RNA: RiboNucleic Acid... A molecule that is present in all living cells and plays an important role in protein production. Ribosome: A cell organelle composed of RNA and protein... The site of protein synthesis. Mutation: A change in the nucleotide-base sequence of a gene or DNA molecule.

Unraveling DNA... In prokaryotic cells (cells that lack a nucleus), DNA forms a loose loop within the cell. In eukaryotic cells (cells with a nucleus), DNA and proteins are bundled into chromosomes. As we discussed in section 4.1, the structure of DNA allows it to hold important information for the cell.  The order of bases (ATGC) on one side of the molecule is a code that carries information.  A gene consists of a string of nucleotides that give a cell information about how to make a specific trait.

Genes and Proteins... DNA is read like a book... From one end to another and in one direction.  The bases form the alphabet of the code.  Groups of 3 bases are the codes for specific amino acids.  Long strings of amino acids form proteins.  Essentially, each gene is usually a set of instructions for making a protein. PROTEINS are found throughout cells and cause most of the differences you can see among organisms.  Proteins act as chemical triggers and messengers for many of the processes with cells.  An organism could have thousands of genes that code for thousands of proteins. RNA (RiboNucleic Acid) is similar to DNA and serves as a temporary copy of a DNA sequence during protein production.  Several forms of RNA help in the process of changing DNA code into proteins. MAKING PROTEIN...  First, a copy of one side of DNA segment is made (this mirror-like copy is RNA... This copy segment is called messenger RNA (or mRNA). After it is made, it moves out of the nucleus and into the cytoplasm of the cell.  Then, the messenger RNA id fed through a protein assembly line. Ribosomes are the “factories” that run the protein assembly lines. During this process, the messenger RNA is fed through a ribosome (3 bases at a time). Then, transfer RNA translate the RNA message ad attack correlating bases (3 at a time) to the messenger RNA... This forms the amino acids necessary to produce protein molecules.

Making proteins...

Changes in Genes... MUTATIONS: Changes in the number, type, and order of bases on a piece of DNA are known as mutations.  Deletion is when a base is left out.  Insertion is when a base is added.  Substitution is when the wrong base is used Do mutations matter?  Three things may happen as a result of a genetic mutation: an improved trait, no change, or a harmful trait. How do mutations happen?  Mutations occur regularly because of random errors when DNA is copied.  Damage to DNA by be caused by abnormal things that happen to cells... Any physical or chemical agent that can cause a mutation is called a mutagen (radiation, UV radiation, asbestos, and chemicals in cigarette smoke).

Mutations continued... Types of mutations >

Sickle Cell Disease... A simple change in an amino acid can cause sickle cell disease.  Sickle cell disease affects red blood cells...  When valine is substituted for glutamic acid (both different amino acid chains), the red blood cells are changed into a sickle shape. This is bad because sickle cells are not as good as carrying oxygen and are more likely to get stuck in blood vessels and cause dangerous clots.

Uses of Genetic Knowledge... GENETIC ENGINEERING: Scientists can manipulate genes within organisms (combining traits). Scientists also use genetic engineering to create new products (drugs, foods, and fabrics). GENETIC IDENTIFICATION: Because your DNA is unique, it can be used like a finger print to identify you. DNA fingerprinting identifies unique patterns in an individual’s DNA. This can be useful in crime scene investigations, identifying family relations, and identifying hereditary diseases.  Only identical twins have the same DNA... Except, more recently, some scientists have created clones, or new organisms that have an exact copy of another organism’s genes.

Homework Now, open your textbooks to page  Define the 4.2 vocabulary terms  Then read the section and begin working on the 4.2 packet 