ZOL 141 1st Edition Lecture 12 Outline of Last Lecture II. Genes and ChromosomesIII. Mendelian inheritance in humansA. PedigreesB. Albinisma. Symptomsb. causesC. Hereditary Deafnessa. Symptomsb. causesIV. Principles of Independent AssortmentV. Branch DiagramsOutline of Current Lecture VI. Variations on Concept of DominanceD. Incomplete dominanceE. CodominanceVII. The Immune Systema. Antigens and Antibodiesb. Blood types and blood transfusionsCurrent LectureVariations on concept of dominance- Incomplete dominance: heterozygous offspring displays a phenotype that is intermediate of both parents’ phenotypeso Snapdragons flower color is controlled by single gene with two alleles, butneither allele is recessiveo R^1= red o R^2= whiteo R1R1xR2R2=R1R2 (pink)o Self cross: R1R2xR1R2= 1:2:1o R1R1= red R2R2= white R1R2= pinko Not blended inheritance because traits are separableo Each genotype has specific phenotype- Codominance: full phenotypic expression of both alleles of a gene pair in a heterozygoteo Blood typeso ABO blood type is controlled by a single gene (denoted I) with three alleles, but two alleles are codominanto I^A=A antigeno I^B=B antigeno I^AI^AxI^BI^B= IAIBo IAIBxIAIB= 1:2:1- Complete dominance: heterozygote will express one of the two homozygous phenotypes- Incomplete dominance: heterozygote will express a phenotype that is intermediate of either of the two homozygous phenotypes- Codominance: heterozygote will express both of the homozygous phenotypes- Multiple alleles: Genes that have more than two allelic forms within a population- Blood type genotypes and phenotypeso I^AI^A, I^Ai-type ao I^BI^B, I^Bi-type bo I^AI^B- type ABo ii- Type OThe Immune System- Antigens and Antibodies- The immune system is a network of cells, tissues, and organs that protect the body from infectiono Antigen: substance to which the immune system can respondo Antibody: protein that is used by the immune system to identify and neutralize an antigeno Antigens found in bodies (like on red blood cells) are known as “self-antigens”o Foreign antigen-pathogeno Self antigen-- Blood types and transfusionso When patients receive transfusions their immune system will attack donor blood cells that contain antigens that differ from self Ex: body makes antibodies to blood type b, or a, depending on what your blood type is. Immune system would attack wrong blood cells being transfused Hemolytic transfusion reaction- Hemolysis: Red blood cells burst: hemoglobin precipitates in kidney- Clumping blocks blood flow in capillarieso To avoid transfusion reaction, donated blood must be compatible with the blood of the patient who is receiving transfusiono Example: Ben has blood type AB and lauren has blood type O. They have a child. Possible blood types?o I^AI^Bx iio Possible gametes: IA IB i io Possible genetypes? iIA iIB iIA iIB- The Bombay Phenotype (Hh blood group)o H antigen is building block for the production of antigens of the ABO blood group (in order to have A antigen, you first must have H antigen) Homozygous recessive individuals (hh) unable to add A or B antigens to surface of cells Phenotypically they are blood type O, even though genotypically they may carry IA IB or i alleles 1/10,000 in India, 1/1,000,000 in Europe Epistasis: interaction of two or more non-allelic genes to control single phenotype- The Rh blood groupo Rhesus blood groupo Most commonly considered is the D antigeno Rh+ individuals make D antigen, Rh- individuals do noto Rh+ will not make anti-D antibodieso Rh- will not make anti-D antibodies, unless they encounter anti-D antigen- Hemolytic disease of the newborno First pregnancy If Rh- woman is carrying an Rh+ fetus Rh+ cells can enter her bloodstream during late pregnancy or childbirth She will begin to produce Rh+ antibodieso Second pregnancy If woman is carrying another Rh+ fetus Rh+ antibodies bind antigen on red blood cells of fetus Fetus’s red blood cells will be destroyedo Doctor prescribes large amount of D