ZOL 141 1st Edition Lecture 12 Outline of Last Lecture II Genes and Chromosomes III Mendelian inheritance in humans A Pedigrees B Albinism a Symptoms b causes C Hereditary Deafness a Symptoms b causes IV Principles of Independent Assortment V Branch Diagrams Outline of Current Lecture VI Variations on Concept of Dominance D Incomplete dominance E Codominance VII The Immune System a Antigens and Antibodies b Blood types and blood transfusions Current Lecture Variations on concept of dominance Incomplete dominance heterozygous offspring displays a phenotype that is intermediate of both parents phenotypes o Snapdragons flower color is controlled by single gene with two alleles but neither allele is recessive o R 1 red o R 2 white o R1R1xR2R2 R1R2 pink o Self cross R1R2xR1R2 1 2 1 o R1R1 red R2R2 white R1R2 pink o Not blended inheritance because traits are separable o Each genotype has specific phenotype Codominance full phenotypic expression of both alleles of a gene pair in a heterozygote o Blood types o ABO blood type is controlled by a single gene denoted I with three alleles but two alleles are codominant o I A A antigen o I B B antigen o I AI AxI BI B IAIB o 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 phenotypes o I AI A I Ai type a o I BI B I Bi type b o I AI B type AB o ii Type O The Immune System Antigens and Antibodies The immune system is a network of cells tissues and organs that protect the body from infection o Antigen substance to which the immune system can respond o Antibody protein that is used by the immune system to identify and neutralize an antigen o Antigens found in bodies like on red blood cells are known as selfantigens o Foreign antigen pathogen o Self antigenBlood types and transfusions o 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 capillaries o To avoid transfusion reaction donated blood must be compatible with the blood of the patient who is receiving transfusion o Example Ben has blood type AB and lauren has blood type O They have a child Possible blood types o I AI Bx ii o Possible gametes IA IB i i o 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 group o Rhesus blood group o Most commonly considered is the D antigen o Rh individuals make D antigen Rh individuals do not o Rh will not make anti D antibodies o Rh will not make anti D antibodies unless they encounter anti D antigen Hemolytic disease of the newborn o 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 antibodies o 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 destroyed o Doctor prescribes large amount of D antigens