BIO 325 1st Edition Lecture 4 Outline of Last Lecture I. Mendelian GeneticsOutline of Current Lecture II. Genetic Complexitiesa. Multiple genesb. Complementary gene actionc. Epistasisd. Redundant genesIII. Penetrance and ExpressivityIV. Binomial Probability FormulaCurrent LectureI. Multiple genesa. Many traits are determined by alleles of more than one genei. Mendel only studied 2 genes that controlled 2 traitsb. What about when two genes control the same trait?i. New phenotype appeared in F2ii. Ratio is still 9:3:3:1 but the 1 is homozygous for the recessive alleles of 2 genesII. Complementary gene actiona. Genes that have effects in pairsi. Ex: Need two genes to make pigment in a flowerb. 9:7 ratio indicative of complementary gene actionc. Complementation test: If the offspring of individuals showing a recessive phenotype do not show the phenotype, then the parents possess recessive alleles of 2 different genes. 1. Ex: Parents have the recessive alleles in different genes causing deafnessa. AAbb x aaBB (both parents deaf)b. F1 generation: AaBb (child not deaf)c. Complementation2. Ex: Parents have the recessive alleles in the same genea. AAbb x AAbb (both parents deaf)b. F1 generation: AAbb (deaf)III. EpistasisThese 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.a. Alleles of one gene mask the effect of alleles of another genei. Ex: Bombay phenotype: In rare instances, parents who are apparently blood group O will have a child that is A or B. 1. What sugars are produced is determined by the genotype at I, but the sugars A and B are attached to red blood cells via Substance H.a. A rare h allele prevents the production of substance H in homozygous individualsb. Regardless of I gene genotypes, individuals homozygous recessive for the h allele have no sugars attached to red blood cells and thus appear to be blood group O.c. Thus h is epistatic to I2. Recessive epistasis: Homozygous recessive alleles of one gene mask the effect of both alleles of another genei. Labrador Retrieversb. bbE: (brown)c. –ee: (yellow)d. B-E-: (black)e. No matter if the b allele is dominant or recessive, ee Labrador retrievers are always yellow. E is recessively epistatic to Bf. 9:3:4 ratio3. Dominant epistasis: Dominant allele of one gene masks the effect of both alleles of another genea. 12:3:1 ratioIV. Redundant genes: A or B is required for maize leaf development. To have leaves, need either A or B. If leaf has aa bb, no leavesa. 15:1V. Environment and chance can also effect phenotypea. Temperature sensitive alleles: Gene products only function in a limited temperature range.b. Temperature-dependent sex determination1. Ex: Crocodiles a. >34 degrees produces malesb. 30-34 degrees produces males and femalesc. <30 degrees produces femalesVI. Penetrance and expressivitya. Penetrance: The frequency at which individuals with a given genotype show the associated phenotypei. Individuals with a certain genotype may not always show the associated phenotypeii. Mendel’s traits were completely penetrantb. Expressivity: The severity/degree to which the phenotype is exhibited. i. Individuals with a certain genotype have a range of phenotypesii. Mendel’s traits did not vary in their expressivityVII. Refer back to Basic probability1. Binomial Probability Formula: P (k number of event n) = [n!/k!(n-k)!] x