Transcript Phenotype
For thousands of years farmers have selectively bred animals to get the traits they want. Farmers mate one animal with qualities they want with another with qualities they want hoping to get animals with both qualities. Case Study: In 1917 the average farmer wanted cows that would produce both milk and beef. Short horn (Durham) cows were popular with the farmers because they had large calves to sell for beef and gave a reasonable amount of milk. The condensed milk factories that bought the farmers’ milk wanted the farmers to keep Holsteins because they produced large quantities of milk. When the milk factories demanded Holstein cows, rather than buy a whole new herd, many farmers got together and purchased a Holstein bull and introduced the breed into their herds. The result was a cow that gave more milk, but still had a large, if not quite so beefy, calf. Gregor Mendel – 1822 Mendel was an Austrian (not Australian) monk. He notice 2 black horses that had a tan foal and wondered how that could happen? (no she wasn’t cheating ) At the monastery he worked in the garden. It was here that he noticed pea plants had 6 different characteristics (traits).*see next slide He observed some traits disappeared and then reappeared in later generations. Baby step through punnet squares http://users.adelphia.net/~lubehawk/BioHELP!/psquare.htm Why peas? Grow Quickly Many different varieties. Self-pollinating Studying on trait at time. Mendel used only purebreds for each trait. (TT, tt) Mendel’s 1st experiment: Round vs Wrinkled He mated a RR X rr. What happened? The offspring are called first generation (F1) and they were all Round. What happened to the wrinkled trait? What happened to the wrinkled Mendel then crossed two offspring from the F1 generation. Ss X Ss In the second generation F2, the wrinkled trait shows up again. Mendel repeated this for the other traits he studied and saw the same phenomenon. Your eyes are green but his are grey and mine are brown All caused by genes…… Now you try it…….. •Cross a Homozygous Red parent with Homozygous blue parent. What are the offspring's: Genotype: •Genotype 100% AA •Phenotype __________ Phenotype: 100% RED •Cross to Heterzygous Parents. •What are the offsprings… •Genotype •Phenotype Genotype AA: Aa: aa 1 : 2 : 1 Phenotype Red : Blue 3 : 1 • • • We each have genes Found on every chromosome They code for traits • You have two genes per trait, • ONE from mom • ONE from dad They’re called ALLELES!! homozygous Two of the same alleles is called, homozygous (YY /Yy) Or…. Two different alleles is called, heterozygous (Yy) heterozygous It’s genetics, It’s genetics: How traits are passed on Phenotype expression of genes, what you look like… These are your traits: - Color –eyes / hair Shape- body / face Genotype the genes that control characteristics Are On….. chromosomes Dominance expressing one trait over another. Recessive is masked but expressed only when both alleles are recessive. Autosomes 1st -22ndpair chromosome, do not determine gender, Sex Chromosomes 23rd pair – determines sex Complete Dominance Incomplete Dominance Codominant Blood Type COMPLETE DOMIANCE -Only Dominant & Recessive -Only 2 Phenotypes CODOMIANCE -Both Alleles expressed equally. -Third phenotype = speckled BB- Black Bb- Black bb- White INCOMPLETE DOMIANCE -Both Alleles blend together -Third Phenotype = new color BB- Black Bb- Speckled bb- White BB- Black Bb- Gray bb- White Animation created by Molly in Ulead Gif Animator www.promotega.org/.../inheritance_patterns.htm Blood Types - Multiple Alleles and Codominance •In humans, there are four blood types (phenotypes): A, B, AB, and O. •Blood type is controlled by three alleles. A, B, O. •O is recessive, OO alleles must be present for the person to have type O. •A & B are codominant. •If you have an A allele and a B allele, their blood type is type AB •Crosses involving blood type often use an I to denote the alleles - see chart. How do they study genes? Uses in everyday life? Doctors take amniotic fluid from the unborn child. (amniocentesis) Scientist then take one cell, break it open and extract the DNA. The picture looks like this… Then they match up the homologous chromosomes to create the following picture x x Male Female What is the difference??? Clearer view Determining Genotypes Test Cross Pedigrees Used to determine genotype of organism. How to testcross: Cross an individual of unknown genotype with an individual with a known genotype. For example: A Red Flower …is it RR or Rr? Testcross with a known (homozygous recessive) to determine genotype. Geno-typically what would this look like? rr _RR_ X ___ Do the Cross…(click to see cross) rr _ Rr__ X ___ aa _AA_ X ___ Phenotype: 100% Red *No matter always yields Dominant trait. Aa x aa Phenotype: 50 % White 50% Red * Recessive white appears. http://courses.bio.psu.edu/fall2005/biol110/tutorials/tutorial4_files/fig_14_6.gif PUREBRED Keeps blood lines pure. Selective Breeding – breeder chooses trait which is passed on. Harmful traits appear. Examples Blue People Czar of Russia HYBRID A mixing of genes. Natural Breeding – nature determines which trait is passed on. Dominant Trait appear thus making stronger healthier individuals. Examples Blake Lab Used to determine Genotypes Shows patterns of inheritance. Uses symbols to represent members of a family. Male Male Female Unaffected Female Affected Blue People of Kentucky Click Picture to see Pedigree The filled in symbol represent individuals who express the trait. Pedigree of the Fugate Family The Story of Hemophilia Late in the summer of 1818, a human sperm and egg united to form a human zygote. One of those gametes, we don't know which, was carrying a newly mutated gene. A single point mutation in a nucleotide sequence coding for a particular amino acid in a protein essential for blood clotting. The zygote became Queen Victoria of England and the new mutation was for hemophilia, bleeder's disease, carried on the X chromosome. A century later, after passing through three generations, that mutation may have contributed to the overthrow of the Tsar and the emergence of communism in Russia. Victoria passed the gene on to some of her children and grandchildren, including Princess Alexandra, who married Nicholas II, Tsar of Russia, in 1894. By 1903, the couple had produced four daughters. The next year, the long awaited male heir appeared - His Imperial Highness Alexis Nicolaievich, Sovereign Heir Tsarevich, Grand Duke of Russia. From his father, the baby Alexis inherited the undisputed claim to the throne of all the Russias. From his mother, he inherited an X chromosome carrying a copy of the mutant gene for hemophilia. Soon after his birth, signs of Alexis' mutant gene appeared. At six weeks, he experienced a bout of uncontrolled bleeding and by early 1905 the royal physicians had concluded that he was suffering from hemophilia. •Inbreeding: creating purebreds •Marrying close relatives, as often occurred in royal families did increase the chances that recessive harmful alleles (like hemophilia) would be inherited. •Impacts of Inbreeding: •Inbreeding has caused many breeds of dogs to have harmful genetic traits. •Dalmations are often deaf, and other dog breeds have high frequencies of epilepsy, blindness, and hip displaysia. BLAKE What race is Blake? First bred in the 1970’s by Wally Conron , the Labradoodle is a very lovable dog, known for their exceptional intelligence and trainability, low to non-shedding coat, low allergy coat, and lack of doggie odor. One of the finest family pet around! A Labradoodle is a crossbred or hybrid dog created by crossing the Labrador Retriever and the Standard or Miniature Poodle. Initially bred for hunting with guns, quick running, swimming, and fighting...and their sense of smell is hardly to be credited."