This chapter explain the chromosomal theory of inheritance and its discovery, explain why sex-linked diseases are more common in human males than females, distinguish between sex-linked genes and linked genes, explain how meiosis accounts for recombinant phenotypes, explain how linkage maps are constructed. | Ch. 15 Warm-Up A white-eyed female fruit-fly is mated with a red-eyed male. What genotypes and phenotypes do you predict for the offspring? Neither Tim nor Rhoda has Duchenne muscular dystrophy (X-linked recessive disorder), but their firstborn son has it. What is the probability their 2nd child will have it? Colorblindness is a sex-linked recessive trait. A colorblind male and a female with normal vision have a son who is colorblind. What are the parents’ genotypes? Definitions: Sex-linked gene Barr body SRY gene Linked genes Linkage map Warm up What is a Barr body? How are linkage maps constructed? (See. Fig. in Campbell 9th ed.) Determine the sequence of genes along a chromosome based on the following recombination frequencies: A-B, 8 map units; A-C, 19 map units; A-D, 20 map units; B-C, 11 map units; B-D, 28 map units. What does a frequency of recombination of 50% indicate? What is the pattern of inheritance of the trait (shaded square/circle) shown in the pedigree? How many chromosomes are in a human cell that is: a) Diploid? b) Triploid? c) Monosomic? d) Trisomic? Warm-Up THE CHROMOSOMAL BASIS OF INHERITANCE CHAPTER 15 What you must know: How the chromosome theory of inheritance connects the physical movement of chromosomes in meiosis to Mendel’s laws of inheritance. The unique pattern of inheritance in sex-linked genes. How alteration of chromosome number or structurally altered chromosomes (deletions, duplications, etc.) can cause genetic disorders. How genetic imprinting and inheritance of mitochondrial DNA are exceptions to standard Mendelian inheritance. Chromosome theory of inheritance: Genes have specific locations (loci) on chromosomes Chromosomes segregate and assort independently Chromosomes tagged to reveal a specific gene (yellow). Thomas Hunt Morgan Drosophila melanogaster – fruit fly Fast breeding, 4 prs. chromosomes (XX/XY) Sex-linked gene: located on X or Y chromosome Red-eyes = wild-type; white-eyes = mutant Specific gene carried on . | Ch. 15 Warm-Up A white-eyed female fruit-fly is mated with a red-eyed male. What genotypes and phenotypes do you predict for the offspring? Neither Tim nor Rhoda has Duchenne muscular dystrophy (X-linked recessive disorder), but their firstborn son has it. What is the probability their 2nd child will have it? Colorblindness is a sex-linked recessive trait. A colorblind male and a female with normal vision have a son who is colorblind. What are the parents’ genotypes? Definitions: Sex-linked gene Barr body SRY gene Linked genes Linkage map Warm up What is a Barr body? How are linkage maps constructed? (See. Fig. in Campbell 9th ed.) Determine the sequence of genes along a chromosome based on the following recombination frequencies: A-B, 8 map units; A-C, 19 map units; A-D, 20 map units; B-C, 11 map units; B-D, 28 map units. What does a frequency of recombination of 50% indicate? What is the pattern of inheritance of the trait (shaded square/circle) shown in the pedigree? How many
