Genetic Code DNA & RNA anyone??

Genetic Code Genetic Anything that relates to heredity This code is a way in which the cell stores the "program" that they need

Is something that we all Know today… DNA & RNA being THE CODE OF LIFE Is something that we all Know today… But, how did they figure out That these molecules were SO extremely important???

Frederick Griffith British microbiologist Did an experiment with the disease-causing bacteria pneumococcus and laboratory mice Griffith's experiment dealt with two strains of the bacteria pneumococcus. One was a virulent (deadly) strain with a smooth polysaccharide coat necessary for infection The other was a non-virulent (non-deadly) strain with a rough coat that could not cause infection

Frederick Griffith Griffith injected one group of mice with the smooth virulent strain and these mice died after a few days. He then injected another group with the rough non-virulent strain and these mice continued to be healthy Griffith took a heat-killed strain of the virulent bacteria and injected it into mice and observed that they did not die. Griffith's fourth experiment was to inject heat treated, killed, smooth virulent strain mixed with the non virulent rough strain. He injected this mixture and found that after a few days the mice died

Transformation When Griffith looked at the blood of the dead mice he found: The virulent bacteria was present and very much alive Griffith retested and found the same to be true Some how, the dead VIRULENT strain transformed the non-virulent strain But how is this possible… It was DEAD?!

Nucleic Acids Once the same experiment was broken down into its most basic building blocks, it was found that the nucleic acids were what caused the transformation They found that if they broke down the deoxyribonucleic acid that the transformation did not occur Therefore, the “genetic code” must be found in this macromolecule

This is a bacterial virus! Bacteriophage Phage = Virus Bacterio = Bacteria This is a bacterial virus!

Alfred Hershey & Martha Chase Radioactively labeled DNA or protein coat of bacteriophage (virus) Found that bacteriophage injected DNA into cells in order to replicate This meant that DNA is the genetic material, not proteins (which make up more than 50% of a chromosome)

Components of a Nucleotide Phosphate group Sugar Nitrogenous (Contains a nitrogen) Base

This will actually help When finding the directionality Of DNA. Sugar A sugar is an organic compound with a carbonyl group C=O This will actually help When finding the directionality Of DNA. The C=O is always pointing At the 5’ end!

The Roof of the Sugar Molecule All sugar molecules have a distinct, house like, shape. At the point of the roof is the C=O. Remember! That always points at the five prime end!

Chargaff’s Theory Found that the #of bases (Purines & Pyrimidines) are the same The # of A’s = # of T’s The # of C’s = # of G’s Found that these bases must be relevant to its matching pair

Watson & Crick Model Chemists found that DNA polymerized through the formation of phosphodiester linkages This concluded a sugar-phosphate backbone By analyzing the total number of purines and pyrimidines it was found that the number of A’s and T’s were equal to the number of C’s and G’s This was called Chargaff’s rule after Erwin Chargaff X-ray diffraction showed a repeating scatter pattern (.34 nm, 2.0nm, 3.4nm) This repeating pattern only makes sense if the molecule is shaped as a double helix

Scatter Pattern X-ray Diffraction Watson & Crick began to analyze the size and geometry of deoxyribose, phosphate groups, and nitrogenous bases. Using things like bond angles, and measurements, they were able to devise 2.0nm probably represented the width of the helix, and .34 was likely the distance between bases stacked in the spiral They arranged two strands of DNA running in opposite directions (5`-3` and 3`-5`)

DNA Size Width of the helix = 2.0nm Length of one full complete turn of helix = 3.4nm Distance between bases = .34nm

Base Pairing Using the x-ray diffraction patterns and measurements, it was found only to work if: Adenine always bonded with Thymine Guanine always bonded with Cytosine This phenomena is called Complimentary Base Pairing

DNA REPLICATION Occurs during S-phase of the cell cycle DNA has a special “complimentary structure that acts as a template for reproduction This means, it allows for simple DNA copying The strand unzips, and the old strand acts for a model to create a new “compliment” The strand copies in two directions: The Leading strand starts at the 3’ end and moves towards the 5’ end The Lagging strand pieces together new nucleotides starting at the replication fork and works toward the 5’

How Does a Cell Make Proteins? The RNA molecule comes out of the nuclear envelope after it is transcribed from DNA (Its like a photocopy) Transcription is the process of creating an RNA strand from a template of DNA nucleotides The process of protein synthesis is called translation Translation refers to the process of converting the “3-nucleotide RNA codons” into amino acids and then into amino acid chains

RNA & Protein Synthesis RNA has very specific blue prints that it uses to build the various amino acids (proteins) called Codons. These codons allow for the difficult job of the synthesis of the many proteins to be grouped into simple readable prints (codons) including “stop and start” codons

RNA Ribonucleic acid is very similar to Deoxyribonucleic acid, except that it contains an extra oxygen then DNA It also contains the nitrogenous base “Uracil” instead of the “Thymine” base. The final and often most obvious difference between the 2 nucleic acids is the fact that RNA is NOT normally a double stranded molecule

DNA & RNA Where DNA is the “book” of your life, RNA is the photocopy DNA = synthesized or replicated in the nucleus RNA = Transcribed from DNA in the NUCLEUS and translated in the RIBOSOME Transcription is a process by which a molecule of DNA is copied into a complementary strand of RNA Because DNA does not leave the nucleus, the DNA information is brought to a ribosome through the use of a messenger RNA

How Does DNA Control a Cell? DNA controls a cell by having the ability to be turned on or off. Remember, DNA makes up our genes Genes are regulated by being turned off or on When a gene is turned on it is said that it is being “expressed” If a gene is turned off it is said that it is “silenced” The ability to control whether or not a gene is expressed or silenced is the GOAL of genetics

A Group of Genes = Operon An Operon will have different segments that are used to control it. The Promoter: is where RNA polymerase binds when beginning transcription The Operator: is where the repressor binds in order to “silence” the genes The Initiator: The codon that signals the start of transcription The Terminator: The codon that signals the end of transcription (also called “stop codon”)

Lac Operon & Hox Gene One of the more famous operons is the Lac Operon Named because it controls the production of a protein called Lactase which breaks down the sugar Lactose found in milk Another important gene mentioned is the Hox Gene This gene controls differentiation of cells in animals and is common among many species

What is a Mutation? A mutation is ANY change to genetic information (DNA) Changing your hereditary information It can happen as simply as an A changing to a T, or a G changing to a C when the DNA is synthesized They can occur in ANY cell It is why our bodies try to be incredibly precise when duplicating our genetic information, ESPECIALLY when transmitting it to the next generation

Types of Mutations Mutations that affect your reproductive cells (often called ‘germ cells’) are called Germ Mutations It is these mutations that are often studied in genetics (Tall, short, yellow, green) Other mutations that affect the other cells are called Somatic mutations (occur in somatic cells Because they do not affect the reproductive cells, somatic mutations are not inheritable Often, somatic mutations are cancerous

2 Levels of Mutation Both somatic & germ mutations can occur at 2 different levels: The level of Chromosomes Involve segments of the chromosome, whole chromosomes, and even sets of chromosomes The level of Genes Involve ONLY individual genes

Chromosomal Mutations Whenever a chromosomal mutation occurs, there is a change in the number or structure of a chromosome There are 4 types of Chromosomal mutations: 1. Deletion 2. Duplication 3. Inversion 4. Translocation

Nondisjunction Chromosomal mutations that involve whole chromosomes or complete sets of chromosomes result from a process known as nondisjunction Nondisjunction is the failure of homologous chromosomes to separate normally during meiosis (Nondisjunction literally means ‘failed to separate’)