BIOLOGY 111 1st Edition Lecture 17 Outline of Last Lecture I. Mendelian GeneticsII. Segregation of AllelesIII. Phenotype and GenotypeIV. Law of independent assortment V. Probability FormulasOutline of Current Lecture I. Epistasis II. Pedigree AnalysisIII. Inherited Disorders in HumansIV. Chromosome Theory of Inheritance Current Lecture- Epistasis a form of gene interaction where one gene effects the expression of the other (masks the phenotypic expression of another)o epistatic alleleo hypostatic allele (opposite of epistatic) o ex.  B controls color, E controls expression of B if a dog gets one dominant E allele (EE or Ee) the color expressed will depend on b allele (BB or Bb -black, bb-brown) if a dog gets a homozygous recessive e allele (ee), the dog will be golden regardless of the b allele - ee is epistatic to b allele- b allele is hypostatic to e allele - Pedigree Analysis - if given genotypes we should be able to recognize type of trait o dominant (AA or Aa) traits are observed in each generation and are more commono recessive (aa) traits tend to skip generations and are less common - Inherited Disorders in Humanso usually due to recessive inheritance (must inherit both (homozygous) recessive alleles)o Cystic Fibrosis o common lethal genetic disease (one in 2500)These 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.o recessive trait (CFTR gene) aa = cystic fibrosis (abnormal CFTR gene) A- (AA or Aa) = normal (normal CFTR gene)- homozygous aa pass on gene and have the gene- homozygous AA do not pass on nor do they have the gene- heterozygous Aa are carriers (they carry the gene but do notshow any of its affects and appear normal)o modifier genes (TGFB1 on chromosome 19) contribute to the severity of cystic fibrosis  influences immune response to infection, leading to more infection, more scarring of lung tissue inherited as a recessive allele- Sickle-cell anemia disease o common, affecting one out of 400 african americanso caused by a substitution of a single aa in the hemoglobin o aa = have the disease, Aa = carriers, AA = do not have the diseaseo Pros are resistant to malarial disease o Cons experience physical weakness, pain, organ damage, and sometimes paralysis o pleiotropic (one gene affects more than one phenotype character) ex. phenylketonuria (reduced hair pigmentation, mental retardation)- Achondroplasia (dwarfism)o rare dominant allele  lethal homozygous dominant alleles heterozygous dominant allele causes dwarfism- two dwarf parents (must each be heterozygous) have .5 chance having a normal child, .5 chance dwarf  homozygous recessive alleles are normal - Huntingtons diseaseo dominant allele disorder o it is a degenerative disease of nervous system- Chromosome Theory of Inheritance - transmission of chromosomes (genes reside on chromosome within the nucleus)- Sex determination Systemo Humans (X-Y)o Insects (X-O)o (Z-Y)o Haploid/Diploid system- Drosophila melanogastero XX-XY sex system, Y not male determining factoro ratio between X chromosomes determines the number of sets of autosomes (X/A) X/A = .5 (male) X/A = 1 (female)- Wild Types are normal in regards to mutation - Y-Chromosome [y-liked genes (mostly sex-determining factors)]- X-Chromosome (x-linked genes) o a phenotype determined by an allele on the x-chromosome o recessive x-linked genes: a normal copy on one X masks the recessive disease allele on the other X (female heterozygous carrier - shows no effect)o a male has a single X chromosome so he will show the effects of any recessive alleles located on the X-chromosome males have only one X chromosomes, they are hemizygous for x-linked gene)o dosage compensation maintains chromosome balance, inactivating one X-chromosome at random in each cell inactivates by XIST gene- Sex-linked genes (if genes found on one of the two chromosomes but not on