BOLOGY 107 Lecture 24 Outline of Last Lecture I II III IV Test Cross Misconceptions Extensions of Mendelian Genetics Pedigree Analysis Chromosomal Basis of Inheritance Outline of Current Lecture V Chromosomal Basis of Inheritance a Sex linked traits b Gene linkage c Recombination frequency d Errors in chromosomal inheritance Current Lecture Chromosomal Basis of Inheritance 1 Sex linked traits a Genes located on the X or Y gene i Inherited chromosome determines allele inherited b Most cases are due to recessive X linked genes very few on Y i Rare in females 1 Double X genes allow for the recessive gene to be cancelled by te dominant healthy gene 2 Must have both recessive genes to show phenotype ii Common in males 1 Only one X chromosome so gene cannot be cancelled by a dominant allele iii Pedigree analysis for X linked trait 1 Affected females are rare usually only a carrier 2 Affected males never come from affected males 3 Inherited by maternal nephews of the affected 4 Descendants of non affected males cannot be affected 2 Gene linkage a Mendelian genetics posit independent assortment i In a cross progeny are can show parent type or recombination of genes b Gene linkage posits that genes on the same chromosome are passed together 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 i Morgan discovered genes crossing over as the way genes on the same chromosome are passed separate 3 Recombination frequency a Differs based on distance between genes on the chromosome b Allows for gene mapping on the chromosome i Approximate unit based on the Rf is the Morgan M 1 1 chance is 1 cM or about 1 million nucleotides 4 Errors in chromosome inheritance a Aneuploidy i A chromosome number different than the exact multiple of the ploidy 1 One too many trisomy 2 One too few monosomy 3 Human examples a Down syndrome Turner s syndrome Kleinfelter s syndrome Triple X 4 Rare for larger chromosomes ii Mechanisms to cause this 1 Non disjunction in meiosis I or II 2 Errors in crossing over or DNA repair a Deleation nucleotides are removed completely b Duplication DNA sequence is completely duplicated c Inversion DNA sequence is completely reversed d Translocation DNA paired with non homologous genes b Polyploidy i Accidental extra set is contained in the cells 1 Error in meiosis or cytokinesis 2 Result of interspecies cross
View Full Document
Unlocking...