BIOB 272 1st Edition Lecture 9Outline of Last Lecture Sex Cont… DominanceI. A few more Examples of Sexual Reproductiona. Anisogamyb. HermaphroditesII. Chromosome Theory of InheritanceIII. Key Features of X-linked InheritanceIV. Molecular Basiss of Dominance-Recessivity:V. Metabolic PathwaysVI. Genotype/Phenotype Relationship- Co-dominance- Multiple alleles- PleiotropyVII. Multiple LociVIII. Genes and Environment: Expression VariationOutline of Current Lecture Dominance Continued, Pedigrees, and LinkageI. Mutiple LociII. Genes & environment: Expression variation III. Pedigree Analysis1. Autosomal, recessive 2. Autosomal, dominant3. X-linked, recessiveThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.4. X-linked, dominantIV. Linkage & Mendel’s Principles1. Dominance2. Segregation3. Independent AssortmentV. LinkageCurrent LectureDominance Continued, Pedigrees, and LinkageI. Mutiple Loci:- Sometimes gene products from different loci may interact with each other to produce unexpected results.- Epistasis occurs when the phenotypic expression of one gene is affected by thaction of another gene.- Example: White and Purple Flowersprecursor=> intermediate=> anthocyaninGenotype CC or Cc + enzyme C= Genotype PP or Pp + enzyme P=**CcPp x CcPp= 9/16 purple, 7/16 whiteII. Genes & environment: Expression variation a. Incomplete penetrance - sometimes the trait predicted by a genotype just does not occur (ex. dominant polydactly)b. Expressivity - sometimes traits are expressed to different degrees (ex. Disease severity)**Both of these show complex interactions of genes with other genes and the environment1. Example: Polydactylypp= normal, Pp and PP= polydactyl (some Pp not polydactyl)Penetrance about 70%2. Example : Some cat fur color spots are temperature-dependentTyrosin (temp-dependent)=> L-DOPA=> Melanin Temperature determines what parts of cats/bunnies body has darker sports (darker around colder areas i.e. the limbs and head)3. Example: BaldnessSex-influenced-Dominant in males, recessive in females related to relative levels of male sex hormonesAutosomal, not sex-linked*, rather sex-influenced Phenotype:Genotype Males Females BB bald bald Bb bald normal bb normal normal*There are other forms of baldness that are sex (X) linkedIII. Pedigree Analysis:Use of family trees and information about affected individuals to: Deduce genetic basis of a disease or trait from its pattern of inheritance Predict risk of disease in future offspring in a family (genetic counseling) Dominant traits often rare in the population Alleles causing recessive traits may be common in the population alleles may come into the pedigree from 2 sources: identity by descent or mutation Often traits are more complex- affected by environment, other genes, and/or sex-limited Basic patterns of inheritance 1. Autosomal, recessive 2. Autosomal, dominant 3. X-linked, recessive 4. X-linked, dominant1. Autosomal recessive traits Trait is often rare in pedigree Trait often skips generations (hidden in Hz carriers) Trait affects males and females equally Most common: Cystic fibrosis, Sickle cell anemia, Phenylketonuria (PKU), Tay-Sachs disease2. Autosomal dominant pedigrees Trait is common in pedigree Trait found in every generation Affected individuals transmit trait to ~1/2 of progeny (regardless of sex) Relatively few examples of human diseases, but non-disease traits can be autosomal dominant-Ex: achondroplasia (skeletal disorder causing dwarfism)3. 3. X-linked recessive pedigrees- Trait is rare in pedigree- Trait may skip generations- Affected fathers do not pass trait to their sons- Males are more often affected than females- Example: color-blindness- red, green vision deficiencyo Much more common in maleso Mom carries recessive gene and then can give to son/daughter (daughter might carry it, but won’t affect her vision)4. 4. X-linked dominant pedigrees- Trait is common in pedigree- Affected fathers pass to ALL of their daughters- Males and females are equally likely to be affected- Extremely unusual because are often lethal (before birth) in malesand only seen in females- ex. incontinentia pigmenti (skin lesions)- ex. X-linked rickets (bone lesions)IV. Linkage & Mendel’s Principles1. Dominance2. Segregation3. Independent Assortment*- Alleles of different genes segregate (or assort) independently of each other. * Usually true if genes on different chromosomesV. Linkage- Eukaryotes : 1000s of genes on relatively few chromosomes- Genes located on nonhomologous chromosomes assort independently; equal probability of all possible gamete combinations- Linkage terms: o Synteny – co-localization of genes on same chromosome in an individual or species. Syntenic genes are physically linked. Genes on same chromosome may be genetically linked as well if they do not meet the predictions of independent