1. Pedigrees

2. Spinal Muscular Atrophy  Severe muscle weakness from birth  Loss of motor neurons in the spinal cord

3. Evaluating Mode of Inheritance Autosomal Dominant?

4. Evaluating Mode of Inheritance Autosomal Recessive?

5. Fred’s Pedigree

6. Get to Know Your Classmate  Pair up (preferably) with someone you do not know  Pick a trait or disease found in your family or you partner’s family  Draw a pedigree depicting the inheritance of the trait/disease  Try to determine the mode of inheritance

7. Dad Mom Vicki Johnny Elizabeth Mildred Bob Joe ZoeySavannahJasmine Elizabeth JeffreyJerryJimmyJoey DougStuart DAM Roger Billy Marion Norm Blondeness in Professor Morrissette’s Family

8. Variations to Mendel’s Laws Extensions and Exceptions

9. Alterations to Mendel’s Ratios  In these cases, genotypic ratio is as Mendel predicted but phenotypic ratio is altered Lethal allele combinations Lethal allele combinations Multiple alleles Multiple alleles Different dominance relationships Different dominance relationships Epistasis Epistasis Penetrance and expressivity Penetrance and expressivity Pleiotropy Pleiotropy Genetic heterogeneity Genetic heterogeneity Phenocopies Phenocopies

10. Lethal Allele Combinations

11. Multiple Alleles  Give a range of phenotypes  Each of us has 2 alleles for any given gene 1 from mom and 1 from dad 1 from mom and 1 from dad  There can be many different alleles for a gene Different alleles are formed by mutations Different alleles are formed by mutations

12. Example of Multiple Alleles -PKU  Phenylketonuria (PKU) Enzyme that breaks down phenylalanine is deficient Enzyme that breaks down phenylalanine is deficient Phenylalanine accumulatesPhenylalanine accumulates There are hundreds of possible alleles There are hundreds of possible alleles Allelic combinations give rise to different phenotypes Allelic combinations give rise to different phenotypes Severe mental retardationSevere mental retardation Moderate PKUModerate PKU Mild PKUMild PKU Asymptomatic PKUAsymptomatic PKU

13. Different Dominance Relationship – Incomplete dominance  The heterozygous phenotype is intermediate between the homozygous dominant and the homozygous recessive  Blended phenotype

14. Different Dominance Relationship – codominance  Phenotypes of both alleles are expressed

15. Codominance –Blood Type

17. Epistasis  One gene affects the expression of another Example: If a dog has the hairless gene, the genes that affect hair color will not be expressed Example: If a dog has the hairless gene, the genes that affect hair color will not be expressed

18. Penetrance and Expressivity  Describe degrees of inheritance  Due to multifactorial inheritance Expression of a gene is influenced by other genes and by environment Expression of a gene is influenced by other genes and by environment  Penetrance =all-or-none expression of a gene 100% of the people who inherit mutant amyloid precursor protein (mAPP) develop Alzheimer disease so mAPP is 100% penetrant 100% of the people who inherit mutant amyloid precursor protein (mAPP) develop Alzheimer disease so mAPP is 100% penetrant  Expressivity =severity of gene expression Polydactyly has variable expressivity Polydactyly has variable expressivity Some have an extra toe and others have an extra toe and an extra finger.Some have an extra toe and others have an extra toe and an extra finger.

19. Pleiotropy  Gene affects several functions Phenotype is varied Phenotype is varied  Example: Porphyria variegata

20. Genetic Heterogeneity  Different genes produce the same phenotype  Example: Hearing loss may be due to one of 132 different genes that follow autosomal recessive inheritance Hearing loss may be due to one of 132 different genes that follow autosomal recessive inheritance B, b =gene for hearing loss type 1 R, r =gene for hearing loss type 2 BBrrbbRR BbRr deaf NOT deaf

21. Phenocopy  An environmentally caused trait that appears to be inherited Example: Phocomelia is a rare genetic disorder whose effects are mimicked by the teratogen, thalidomide Example: Phocomelia is a rare genetic disorder whose effects are mimicked by the teratogen, thalidomide Example: AIDs transmission from mother to offspring Example: AIDs transmission from mother to offspring