Modern Genetics

Multiple Alleles More than two alleles can be inherited –Example: Blood Types –Alleles= I A, I B, i Blood Type (Phenotype) Type of Antigen Possible Genotypes AAI A I A, I A i BBI B I B, I B i AB IAIBIAIB ONoneii

Multiple Alleles: Cont’d Agglutination –Blood coagulates or clumps together –Antibodies recognize antigen on surface of blood and attack it i.e. B antibodies recognize B antigens Phenomenon occurs because of genotypes!

Multiple Alleles: Punnett Squares Heterozygous A x Heterozygous B Genotypes: I A i x I B i Type O x AB Genotypes: ii x I A I B

Chromosomes & Sex Determination 23 pairs of chromosomes found in nuclei of a human cell or 46 total chromosomes Pairs 1-22: Somatic Pair #23: Sex- determining chromosome Karyotype 1.Extract chromosomes from nucleus of a cell 2.Pair up matching chromosomes 3.Arrange chromosomes by size

Sex Determination Female: XX Male: XY Baby’s sex determined by male –Mom  X –Dad  X or Y X chromosome Y chromosome

Sex-Linked Traits The X chromosome carries the trait, not the Y MaleFemale Normal Carrier Diseased Person

Sex-Linked Traits Examples Sex-linked diseases: Color blindness, hemophilia Example: Carrier Female & Normal Male

Incomplete Dominance Contrasting alleles 1 allele is partially dominant Intermediate traits are expressed Example: Cross Red Flower & White Flower F1 GenerationF2 Generation

Codominance Heterozygous with both alleles expressed Homozygous red cow mates with homozygous white bull C R C R x C W C W C R C W (roan)

Polygenic Traits Traits controlled by 2 or more genes –Additive effect Example: Height  Combination of all body parts put together; determined by many genes on different areas of chromosomes

Environmental Factors The environment an organism lives in can change its phenotype Examples: Snowshoe hare Example: Hydrangea pH and presence of iron affect color