2. Mid-digital hair – dominant Tongue rolling – dominant Widow's peak – dominant Earlobes – dominant Hitchhiker's thumb less than 45° - dominant Relative finger length An interesting sex influenced (not sex-linked) trait relates to the relative lengths of the index and ring finger. In males, the allele for a short index finger (S) is dominant. In females, it is recessive. In rare cases each hand may be different. If one or both index fingers are greater than or equal to the length of the ring finger, the recessive genotype is present in males and the dominant present in females. MENDELIAN GENETICS AND HUMANS Human Traits
3. MENDELIAN GENETICS AND HUMANS Human Blood Groups Let the allele for blood type be represented by “I” I A = Type A (dominant) I B = Type B (dominant) i = Type O (recessive) codominant
4. MENDELIAN GENETICS AND HUMANS Human Blood Groups I A = Type A (dominant) I B = Type B (dominant) i = Type O (recessive) Anti A, Anti B Type O ii O None Type AB I A I B AB Anti-A Type B I B i or I B I B B Anti-B Type A I A i or I A I A A Antibody Antigen (phenotype) Genotype Blood Types
5. MENDELIAN GENETICS AND HUMANS Human Blood Groups What are the genotype and phenotype ratios of the offspring between a Type AB male and Type O female? Parent genotypes: I A I B x ii Therefore: F1 genotypes 1 I A i : 1 I B i F1 phenotypes 1 Type A : 1 Type B I B i I A i i I B i I A i i I B I A
6. MENDELIAN GENETICS AND HUMANS Human Blood Groups Is it possible for a Type A father and a Type B mother to produce Type O children? Let’s assume the parents are homozygous I A I A and I B I B Parent genotypes: I A I A x I B I B Parent gametes: I A I A x I B I B Therefore: F1 genotypes 100% I A I B F1 phenotypes 100% Type AB blood None of the children have O-type blood. So let’s assume the parents are both heterozygous I A I B I A I B I B I A I B I A I B I B I A I A
7. MENDELIAN GENETICS AND HUMANS Human Blood Groups Is it possible for a Type A father and a Type B mother to produce Type O children? Let’s assume the parents are heterozygous I A i and I B i Parent genotypes: I A i x I B i Parent gametes: I A i x I B i Therefore: F1 genotypes 25% I A I B 25% I A i 25% I B i 25% ii F1 phenotypes 25% Type A, 25% Type B, 25% Type AB, and 25% Type O So it IS possible!!! i i I A i i I B i I A I B I B i I A
8. MENDELIAN GENETICS AND HUMANS Inheritance Patterns Autosomal recessive: Involves a recessive allele on a non-sex chromosome Autosomal dominant: Involves a dominant allele on a non-sex chromosome X-linked recessive: Involves a recessive allele on the X-chromosome X-linked dominant: Involves a dominant allele on the X-chromosome Y-linked: Involves an allele on the Y-chromosome
