Non-Mendelian Inheritance PDF

- Heterozygotes (pink flowers) Non-Mendelian Inheritance: P: 1:2:1 - hetero is intermediate between two homo 1. Lethal Genotypes - a certain genotype (combination of alleles) that causes death 3. Codominance - distinct, hetero...

- Heterozygotes (pink flowers) Non-Mendelian Inheritance: P: 1:2:1 - hetero is intermediate between two homo 1. Lethal Genotypes - a certain genotype (combination of alleles) that causes death 3. Codominance - distinct, hetero is not /disease intermediate - usually stillbirth or miscarriage - where 2 alleles are expressed (multiple - dies early in development alleles) in heterozygous individuals - no interaction will happen, both of them Two types: will appear (1:2:1) (a) Lethal Dominant Ex. Red Cow + White Cow = Roan Cow -whenever the dominant allele is present, Blood type the disease will appear on that organism or worse can cause death still- birth (Huntington’s Disease) G: 1:2:1 P: 0:1 -whenever dominant allele is present, it can cause death (b) Lethal Recessive - in order for it to be manifested on the organism, it must receive two copies of - type A is of equal dominance with type B, recessive traits. (Sickle cell anemia) meaning whenever A and B are present G: 1:2:1 P: 3:0 then both of them will be expressed - A and B are dominant over O, meaning if in Lethal Genotypes... either A or B will be paired with O then A or Mendel's Laws are still correct and still B will be inherited being followed: safest combination (hetero-hetero) - two alleles (one dominant + One - we cannot see any other blood type recessive) outside the cross - producing the 1:2:1 genotypic ratio - Only phenotypic ratio that is changed 4. Overdominance - heterozygote can express a phenotype 2. Incomplete Dominance that is more extreme than either parent - one allele is not completely dominant over - heterozygote has better characters the other; Causing the heterozygote to have (healthier, bigger,etc.) a third different phenotype -(1:2:1) - the dominant trait is not entirely dominant over the recessive Heterosis - heterozygote that possesses - due to INTERACTION, not the same as the traits that are extreme/supreme than the blending parents Ex. Four o'clock flower color Blending in flowers Sickle Cell Anemia - Homo Dominant (red flowers) SS= sickle cell anemia - Homo Recessive (white flowers) SA= malaria resistance (good) AA= Malaria susceptibility EX. Hypercholesterolemia - some individuals have extremely high cholesterol 5. Penetrance from birth, others control with diet and - sometimes the same genotype will not exercise and lead to normal lives produce the phenotype in all individuals - has genotype, but no phenotype (Penetrance vs. Expressivity) Both follow Mendel’s laws Penetrance - genotypic ratio (1:2:1) - the percent of individuals who have a - phenotypic ratio is affected certain genotype and show the expected phenotype Both have to do with "amount" phenotype - "Mendel's traits penetrance = 100% is present - Some traits penetrance is less than 100% - Penetrance (all or none, person is affected - decreased penetrance or "low penetrance" with disease or not) means that some people inherit genotype - Expressivity (severity of the phenotype) and yet do not show the phenotype. - penetrance is calculated as: 7. Pleiotropy - One gene causes more than one No. of individuals who have genotype. and phenotype expected phenotype - Occurs when one gene controls more than Total no. of individuals who have genotype one. pathway or is expressed in more than (any phenotype) one body part - one gene governs a lot of characters - usually decrease caused by interaction of (mutation of this gene could lead to additional environment complications of a lot of characters) - even if you have the gene, there is a tendency that it will not manifest, either fully Ex. manifested or not manifested at all (all or One gene makes connective tissue (fibrillin nothing) (0 or 100) 1 or FBM 1) - due to coiling of the gene by the protein - needed for lens of eye - heart muscle limbs, skin, and muscles 6. Expressivity - sometimes the same genotype will Therefore mutation in this one gene will produce different “degrees” of phenotype in cause defects in eye sight, heart attacks individuals and weakness in muscles and limbs - genotype with phenotype but vary intensity *Marfan Syndrome *Pleiotropy in chickens Expressivity - the severity or extent of the phenotype an 8. Phenocopies individual shows - trait is not genetic at all - you may have the gene, it will manifest, (environmentally caused trait that appears but the degree of manifestation varies from to be genetic/ inherited) or person to person Environmentally caused phenotype that is the same as an inherited phenotype) - there is a trait that emerged that is not found in the genome Ex. Hydrangea macrophylla flower color depends on soil pH Acidic soil - blue Basic soil - red (b) Locus heterogeneity Phocomelia - more than one gene producing the same (when infants were subjected they have phenotype normal genome; it was due to what Ex. Retinitis Pigmentosa happened in the womb environment) Osteogenesis Imperfecta (chromosome 17 - COL1A1) 9. Genetic Heterogeneity (chromosome 7 - COL1A2) - more than one gene producing the same phenotype Two types: 11. Epistasis (a) Allelic heterogeneity - product of one gene masks or changes the - more than one allele in the gene produce expected phenotype of one or more other the same phenotype genes - more than one allele that would produce or - two genes interact with one another but lead to the same manifestation of a trait, one gene masks over the effect of the other regardless if dominant allele or recessive gene. allele it will code for the same manifestation of gene Types of Epistasis: - in reality there are a lot of variations (a lot (a) Recessive Epistasis (9:3:4) of dominant in every variation) - homozygous recessive is epistatic or masks the effect of the other gene Ex. - A dominant to a Cornelia de Lange Syndrome - B dominant to b - has three variations (allele A, B, and C) aa is epistatic to B and bb - but regardless which allele will be - 9:3:4 possessed, one will still have Cornelia Waardenburg-heterochroma Rats Ex. A - brown (agouti) a - black C - pigment c - white (albino) 9 A_C_ - brown 3 A_cc - white 3 aaC_ - black 1 aacc - white (9:3:4) Labrador (dogs) (b) Dominant Epistasis (12:3:1) - One gene when dominant is epistatic to the other - A dominant to a - B dominant to b (12:3:1) (c) Dominant Suppression Epistasis (13:3) (d) Duplicate Recessive Epistasis (9:7) - one gene when dominant is epistatic to the - either gene when homozygous recessive other; one gene when homozygous is epistatic to the effects of the dominant recessive is epistatic to the homozygous allele of the other gene recessive state of the first stage - A dominant to a - A dominant to a - B dominant to b - B dominant to b aa epistatic to B - A epistatic to B and bb bb epistatic to A bb epistatic to aa A and bb is same expression (e) Duplicate Dominant Epistasis (15:1) - when dominant is epistatic to the recessive of the other - A dominant to a - B dominant to b A epistatic to bb B epistatic to aa Complete dominant (3:1) - heterozygotes are phenotypically identical to homozygous dominant (f) Polymeric Gene Interaction (9:6:1) - two dominant alleles have similar effect when they are separate, but enhanced effect when come together Multiple alleles - many variants or degrees of a phenotype occur Polygenic Inheritance - multiple genes influence the expression of a trait that is usually quantitatively variable (g) Novel Phenotypes (9:3:3:1) - new phenotypes are produced from the interaction between dominants and between both homozygous recessive - A dominant to a - B dominant to b A interacts B - new phenotype Aa interacts bb - new phenotype - one character only but 4 phenotypes