Gregor Mendel - father of Genetics and 18th century Austrian monk -studied pea plants, developed idea of traits and inheritance Genetics - The study of heredity. Heredity - The passing on of traits from an organism to its offspring. Trait - characteristics of an organism Genes – (allele) Units of heredity. One set from each parent. Dominant - One gene dominates another. - ex: Brown eyes dominate blue eyes. Recessive - Weaker trait; Ex.blue eyed genes are dominated by Brown eyed genes. Purebred - Genes that are the same for a given traits. Ex. - 2 Brown eyed genes. BB BB or Bb bb Hybrid – Two different types of genes for a given trait. Example one (B) brown eyed gene and one blue (b) eyed gene. Bb 1 Incomplete Dominance - Neither gene in an allele masks the other. Ex : Red rose and white rose have pink offspring. WW RW RR Law of Segregation - One gene (chromosome) from each pair of parent’s genes goes to egg or sperm cell. Independent Assortment - Each set of genes is independently inherited. - random sorting - Ex. Tallness gene is randomly assorted from eye color gene. *** Some genes that are close to each other on a DNA molecule do not follow this rule. Principles of Modern Genetics - Traits, or characteristics, are passed on from one generation to offspring. - An organism inherits genes in pairs, one from each parent. - Some genes are dominant and some are recessive. - Dominant genes hide recessive genes. - Some genes are not dominant or recessive; they blend traits, incomplete dominance. 2 Genetics and Probability -Probability is the chance or likelihood that something will happen. Punnett Squares - A chart showing the possible gene combinations (or chromosomes) in a cross between two organisms. Phenotype - What the organism looks like. Ex. Brown Dog Genotype - Gene makeup of organism. Ex. Bb - A brown dog with one brown gene and one white gene. BB - A brown dog with 2 brown genes. bb – A white dog with 2 white genes Question : Cross a white dog (bb) with a black dog (Bb). B b Phenotype = 50% Bb b 50% bb Bb b b Genotype = 50% Brown Bb 50% white b b b 3 Chromosomes Chromosomes - rod-like shaped structures made of coiled DNA Walther Flemming - (1882 , German) - discovered chromosomes Walter Sutton - American 1902 : Discovered that chromosomes come in pairs. - Sperm and egg cells have half the normal number of chromosomes. Theory of Heredity - Genes are carried from parents to their offspring on chromosomes. Meiosis - process of cell division producing sex cells - each cell has a haploid amount of chromosomes Haploid - 1/2 the number of chromosomes (sex cells) Diploid - normal number of chromosomes ( somatic or body cells ) 4 Thomas Hunt Morgan - American Zoologist discovered sex chromosomes in fruit flies. Sex Chromosomes - X and Y chromosomes determine sex. - X is larger than Y Male = XY Female XX Hugo De Vries - Dutch Botanist discovered mutations in primroses. Mutation - A change in a gene or a chromosome. A mutation in a somatic cell only affects that organism. A mutation in a sex cell affects its offspring. Most mutations are harmful or neutral. Mutations happen when DNA is damaged. Causes (Mutagens) - X rays, UV rays, Pollutants, toxic chemicals, old age Beneficial - Some mutations help an organism survive in an environment. A mutation in a plant that can produce a toxin that protects it from insects. A major force behind evolution. 5 Human Genetics Y chromosome - Triggers the production of the male hormone testosterone. - Testosterone is a hormone that controls male secondary sexual characteristics. i.e. deep voice, Adam’s apple Multiple Alleles - Some characteristics are control by more than two alleles. - example - blue, brown and green eyed genes Blood Surface Proteins - Two alleles A , B ( O is lacking in all three ) - codominant - all are expressed Mom- AB A B 50% = AA A AA AB 50% = AB A AA AB Dad - AA Inherited Diseases - A mutation in a gene that codes for an important protein. - example : Sickle Cell Anemia- A mutation in the gene for hemoglobin. Cause red blood cell to have a sickle shape. S = gene mutation (sickle cell) A = Normal gene A S 25%=Normal AA AS A 50%= Carriers S AS SS 25%= Sickle cell 6 Genetic Diseases - Mutations can hide in hybrids. - Some have benefits. Sickle cell- Carriers have some protection from malaria. Cystic Fibrosis - May have offered some resistance to typhoid. Genetic Engineering - Future of modern medicine. - Actually correcting the problem “gene” that causes the disease. Nature Vs Nurture- Heredity Vs Environment - Twin studies suggest a 40% nature and 60% nurture. Sex-linked Traits- Traits that are on X chromosome. - color blindness, hemophilia Pedigree - A family tree showing the frequency of a trait. males females Human Genetic Disorders Nondisjunction - The failure of a chromosome pair to separate during meiosis. - Body (somatic) cells may have more or less than normal amount of chromosomes, usually lethal. Karyotype - Shows the size, shape and number of chromosomes in an organism. Down Syndrome: An extra chromosome (trisomy) on the 21 chromosome. Have various physical and developmental problems, and mental retardation. 7 DNA Deoxyribonucleic Acid - “ The Blueprints of Life” contains all the information to make an organism. - DNA stores and passes on genetic information from one generation to the next. - DNA is a large molecule. James Watson and Francis Crick - Nobel prize winners for their discovery of the structure of DNA. Rosalind Franklin and Maurice Wilkins - Used X rays to discover the shape of DNA. Structure of DNA - Double helix, looks like a twisted ladder. - Each rung (step) is made of two nitrogen bases connected to each other. Nitrogen bases - Adenine (A), Thymine (T), Guanine (G), and Cytosine ( C ) Rules for Connection A (adenine) only combines with T (thymine) G ( guanine ) only combines with C ( cytosine ) 8 Reading Strand - Only one side of the ladder is read, the reading strand. Complimentary strand - Opposite strand of reading strand. A copy incase reading is damaged. DNA is read like a book. The words are codons. Codons are 3 nitrogen bases long. Ex: ATT or GTC Each codon codes for an amino acid. These amino acids made in ribosome make up proteins. Genes code for Proteins DNA Replication: Replication: The DNA molecule unzips itself and is both sides are copied. In interphase stage of Mitosis a complete copy is made. RNA - Ribonucleic Acid RNA is an opposite copy of DNA RNA is a messenger. It takes information out of nucleus to ribosomes. Does not contain thymine, uracil ( U ) connects with Adenine ( A ) 9 Applied Genetics Plant and Animal Breeding Selective Breeding - crossing plants or animals with desirable traits to produce offspring with those traits. Hybridization -Crossing two organisms (usually from the same or close species) with different variations of a trait. Examples - corn, rice, mules, dogs. + = Inbreeding - Crossing animals or plants with similar genes. - Used to keeps animals or plants purebreds. Genetic Engineering -The process in which genes are transferred from one organism to another or designed. 10 Recombinant DNA - Inserting a gene into another genome. Plasmid - Free floating circular pieces of bacterial DNA. Bacterial Transformation; 1) Cut Plasmid with a restriction enzyme. Break the circular DNA. Leaving two sticky ends. 2) Insert a gene. Human gene for insulin. Inserted into a plasmid 3) Force plasmid into bacteria cell. Placed in a bacteria. 4) Plasmid forces bacteria to make gene product. Bacteria produce insulin. Products of Genetic Engineering Medical - Using bacteria to make drugs, hormones, and enzymes. - Correcting genetic diseases. - Designing genes to combat disease. 11 Agriculture - Genetically altering plants for better produce. - Genetically altering plants for disease prevention. Many plants that you buy in stores are genetically modified. - ex: tomatoes , corn, and wheat Gel Electrophoresis - Running cut pieces of DNA on an agarose gel for analysis. Restriction Enzymes - Enzymes that cut DNA at specific sites. - Identifies an organism through its genes, used in forensics. ex: crime scenes, food analyses, and endangered species protection PCR- Polymerase Chain Reaction - Making multiple copies of a segment of DNA. - forensics and the study of genes 12 Types of Gene Therapy in vivo - “ in life ” - placing good genes in cells invitro - “ in glass ” - correcting the genetic disease inside a test tube in situ - “ in position ” - correcting the disease inside a cell in the body Future of Genetics Gene Therapy : - inserting “good” genes in a virus virus infects human cell , inserts good gene - inserting corrected genes into an actual cell - finishing of the Human Genome Project The Secret Code of Life 13 .