Mendelian Inheritance Patterns PDF

Molecular Biology and Genetics Mendelian inheritance patterns 1 Inheritance Patterns Mendelian Non-Mendelian Dominant Autosomal...

Molecular Biology and Genetics Mendelian inheritance patterns 1 Inheritance Patterns Mendelian Non-Mendelian Dominant Autosomal Recessive All chromosomes other than sex chromosomes Dominant X-linked Next Lecture x - chromosome Recessive 2 1  Mendelian Inheritance Patterns Homozygous I- Autosomal; a) Dominant inheritance (or diseases) Genotype AA Aa aa Phenotype Affected Affected Normal Heterozygous eee eee eee eee eee eee eee 3 Mendelian Inheritance Patterns I- Autosomal; a) Dominant inheritance (or diseases) characterized by: - There are no carriers - Males and females will inherit the disease in equal proportions - An affected offspring has an affected parent (unless the affected is expressing a new mutation) - An affected individual with one affected parent will have 50% affected offspring 4 2  Mendelian Inheritance Patterns I- Autosomal; a) Dominant inheritance (or diseases) characterized by: - Two heterozygous parents will have 75% Affected 25% Normal 50% Heterozygous affected 50% Homozygous A a (25% Affected 25% normal) A AA Aa a Aa aa - Homozygous dominant allele individuals usually have more severe symptoms 5 Mendelian Inheritance Patterns I- Autosomal; a) Dominant inheritance (or diseases) : Examples of autosomal dominant disorders include - Achondroplasia (dwarfism) - Marfan syndrome - Hypercholesterolemia - β-thalassemia - Polycystic kidney disease 6 3  Mendelian Inheritance Patterns Homozygous I- Autosomal; b) Recessive inheritance (or diseases) : Genotype AA Aa aa Phenotype Normal Normal Affected Heterozygous (Carrier) Consanguineous matting (between relatives) 7 Mendelian Inheritance Patterns I- Autosomal; b) Recessive inheritance (or diseases) characterized by: - Affected individuals may have two unaffected parents - 25% of the children of two heterozygote (carrier) parents are affected - Two affected individuals have 100% affected children - The trait occurs with the same frequency in both sexes - Heterozygote individuals are carriers 8 4  Mendelian Inheritance Patterns I- Autosomal; b) Recessive inheritance (or diseases) : Examples of autosomal recessive disorders include - Albinism - Cystic fibrosis - Phenylketonuria - Sickle cell anemia 9 Mendelian Inheritance Patterns II- X-linked inheritance The name is X-linked not sex linked….. Why? Mendelian inheritance divided into autosomal and x-linked ….. Why? X chromosome is five times larger than Y chromosome, and if females expressed all of the genes on both X chromosomes, they would express many genes much more than males. Lyon Hypothesis To keep gene dosage equal between the sexes, Mary Lyon proposed that one of the two X chromosomes in every cell of female mammals is inactivated (Barr body). Inactivation is random as to the origin (may of maternal or paternal) 10 5  Mendelian Inheritance Patterns II- X-linked inheritance Lyon Hypothesis 11 Mendelian Inheritance Patterns II- X-linked inheritance a) Dominant b) Recessive The most common X-linked disorders are recessive in nature that characterized by; - Males cannot be carriers (No Father to son transmission) - Males are affected substantially more often than females - An affected male will have 100% carrier daughters & 100% normal sons, if the mother is not a carrier - A carrier mother will have 50% affected sons and 50% carrier daughters - An affected mother will have 100% affected sons and 100% of her daughters will be carriers, if the father is unaffected. 12 6  Mendelian Inheritance Patterns II- X-linked inheritance b) Recessive Examples of X-linked recessive disorders include - Hemophilia A - Lesch-Nyhan syndrome - Duchenne muscular dystrophy - Red-Green color blindness 13 Mendelian Inheritance Patterns N.B. Sex-influenced traits: - Are autosomal traits that are influenced by sex e.g. Male & female Pattern Baldness & Length of index finger 14 7  Mendelian Inheritance Patterns Activities Report a short note on - Lesch-Nyhan syndrome as a cause of metabolic gout 15 16 8