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Non-Mendelian Genetics Mendelian Genetics: Dominant & Recessive Review One allele is DOMINANT over the other (because the dominant allele can “mask” the recessive allele) genotype: PP genotype: pp genotype: Pp phenotype: purplephenotype: white phenotype: purple Review Problem: Dominant & Recessive In pea plants, purple flowers (P) are dominant over white flowers (p). Show the cross between two heterozygous plants. GENOTYPES: - PP (25%) Pp (50%) pp (25%) - ratio 1:2:1 PHENOTYPES: - purple (75%) white (25%) - ratio 3:1 P p P PP Pp p Pp pp Non-Mendelian Genetics Incomplete Dominance Codominance Multiple Alleles Polygenic Traits Sex-Linked Traits Fur colors black agouti yellow Incomplete Dominance a third (new) phenotype appears in the heterozygous condition as a BLEND of the dominant and recessive phenotypes. Ex - Red (RR) + White (WW) = Hybrid Pink (RW) RR = red WW = white RW = pink Problem: Incomplete Dominance Show the cross between a pink and a white flower. GENOTYPES: - RR (0%) RW (50%) WW (50%) - ratio 1:1 R W W RW WW W RW WW PHENOTYPES: - pink (50%); white (50%) - ratio 1:1 Codominance in the heterozygous condition, both alleles are expressed equally with NO blending! Represented by using two DIFFERENT capital letters. Example: Sickle Cell Anemia - NN = normal cells SS = sickle cells NS = some of each Codominance Example: Speckled Chickens BB = black feathers WW = white feathers BW = black & white speckled feathers Notice – NO GRAY! NO BLEND! Each feather is either black or white Codominance Example: Rhodedendron R = allele for red flowers W = allele for white flowers Cross a homozygous red flower with a homozygous white flower. Codominance Example: Roan cattle cattle can be red (RR – all red hairs) white (WW – all white hairs) roan (RW – red and white hairs together) Codominance Example: Appaloosa horses Gray horses (GG) are codominant to white horses (WW). The heterozygous horse (GW) is an Appaloosa (a white horse with gray spots). Cross a white horse with an appaloosa horse. W W G GW GW W WW WW Problem: Codominance Show the cross between an individual with sickle-cell anemia and another who is a carrier but not sick. N S GENOTYPES: - NS (50%) SS (50%) - ratio 1:1 S NS SS PHENOTYPES: - carrier (50%) sick (50%) - ratio 1:1 S NS SS MULTIPLE ALLELES • Many traits have more than 2 alleles that determine the phenotype Forensic Science T. Trimpe 2006 http://sciencespot.net/ What is blood made up of? • The red blood cells contain hemoglobin, a protein that binds oxygen. Red blood cells transport oxygen to, and remove carbon dioxide from, the body tissues. The white blood cells fight infection. The platelets help the blood to clot, if you get a wound for example. The plasma contains salts and various kinds of proteins. Blood Facts The average adult has about FIVE liters of blood inside of their body, which makes up 7-8% of their body weight. Blood is living tissue that carries oxygen and nutrients to all parts of the body, and carries carbon dioxide and other waste products back to the lungs, kidneys and liver for disposal. It also fights against infection and helps heal wounds, so we can stay healthy. There are about one billion red blood cells in two to three drops of blood. For every 600 red blood cells, there are about 40 platelets and one white cell. http://www.bloodbankofalaska.org/about_blood/index.html History of Blood Groups and Blood Transfusions •Experiments with blood transfusions have been carried out for hundreds of years. Many patients have died and it was not until 1901, when the Austrian Karl Landsteiner discovered human blood groups, that blood transfusions became safer. He found that mixing blood from two individuals can lead to blood clumping. The clumped RBCs can crack and cause toxic reactions. This can be fatal. • http://nobelprize.org/medicine/educational/landsteiner/readmore.html Multiple Alleles there are more than two alleles for a gene. Ex – blood type consists of two dominant and one recessive allele options. Allele A and B are dominant over Allele O (i) Blood Types Type A Type B Type O Type AB AUTOSOMAL CHROMOSOME A The alleles for Blood group are in the same place on the chromosome 9. However the genes have a different code giving the different blood group B Susan one alleles from Pete and one from Susan. Pete AB0 blood grouping system Blood group A If you belong to the blood group A, you have A antigens on the surface of your RBCs and B antibodies in your blood plasma. Blood group B If you belong to the blood group B, you have B antigens on the surface of your RBCs and A antibodies in your blood plasma. Blood group AB If you belong to the blood group AB, you have both A and B antigens on the surface of your RBCs and no A or B antibodies at all in your blood plasma. Blood group O If you belong to the blood group O (null), you have neither A or B antigens on the surface of your RBCs but you have both A and B antibodies in your blood plasma. Multiple Alleles: Blood Types (A, B, AB, O) Rules for Blood Types: A and B are co-dominant (Both show) IAIA = type A IBIB = type B IAIB = type AB A and B are dominant over O (Regular dom/rec) IAi = type A IBi = type B ii = type O Allele Can Can (antigen) Donate Receive Possible on RBC Blood Blood Phenotype Genotype(s) surface To From A IAi IAIA A A, AB A, O B IBi IBIB B B, AB B, O AB AB A, B, AB, O O A, B, AB, O O AB O IAIB ii Problem: Multiple Alleles Show the cross between a mother who has type O blood and a father who has type AB blood. GENOTYPES: - Ai (50%) Bi (50%) - ratio 1:1 PHENOTYPES: - type A (50%) type B (50%) - ratio 1:1 i i A Ai Ai B Bi Bi Problem: Multiple Alleles Show the cross between a mother who is heterozygous for type B blood and a father who is heterozygous for type A blood. GENOTYPES: -AB (25%); Bi (25%); Ai (25%); ii (25%) - ratio 1:1:1:1 A i B AB Bi PHENOTYPES: i -type AB (25%); type B (25%) type A (25%); type O (25%) - ratio 1:1:1:1 Ai ii Polygenic Traits traits produced by multiple genes example: skin color Sex-Linked Traits Gene is attached to the X chromosome only, not found on the Y chromosome at all. (women have XX, men have XY chromosomes). These disorders are more common in boys. examples: red-green colorblindness Sex-Linked Traits in males, there is no second X chromosome to “mask” a recessive gene. If they get an X with the disorder, they have it. Girls must inherit defective X’s from both parents. Sex-Linked Traits A: 29, B: 45, C: --, D: 26 Normal vision A: 70, B: --, C: 5, D: - Red-green color blind A: 70, B: --, C: 5, D: 6 Red color blind A: 70, B: --, C: 5, D: 2 Green color blind