I. Relating MendelismA. Physical Basis During Sexual Life Cycles1875: Mitosis research by cytologist and 1890s: Meiosis Chromosome Theory of Inheritance is a basic principle that states genes are located on chromosomes and that the behavior of chromosomes during meiosis accounts for inheritance patterns.B. Gene To A Specific ChromosomeThomas Hunt Morgan, embryologist from Columbia University, says specific genes are on specific chromosomes. He did not believe Mendelism or chromosome theory.a. Choice of Experimental OrganismMorgan uses fruit flies to experiment because they breed quickly and produce hundreds at each mating. It has only four chromosomes -- three pair of autosomes and one pair of sex chromosomes. 1. Wild Type: the normal phenotype for a character of an organism2. Mutant Phenotype: abnormal (or mutated) phenotype for a character of an organismb. Discovery of Sex LinkageMorgan discovered that only male fruit flies possessed white eye meaning that the gene had to be sex-linked. Since females have two X chromosomes both of them has to have the allele for white eyes for them to acquire that phenotype. The trait is recessive.1. Sex-Linked Genes: genes located on the sex chromosomesC. Linked Genes Inherited TogetherWhen genes are linked together, they generally resemble the phenotypes of the parents and the F1 generation. Although major of the phenotypes match those of the parents, all possible phenotypes were represented.1. Linked Genes: genes that are passed together from parent to offspring as a unitD. Genetic RecombinantsDefinitions: The production of offspring with new combinations of traits inherited from two parents. a. Recombinants of Unlinked GenesThere is a 50% frequency of recombinants for genes located on different chromosomes. It occurs at metaphase I of meiosis on homologous chromosomes that have unlinked genes. Ratio -- 1:1:1:11. Parental Types: having the phenotype of the P generation2. Recombinants: new combinations of a specific characterb. Recombinants of Linked GenesWhen completely: Ratio 1:1:0:0 with only the P generation phenotype.E. Recombination Data To Map Genetic Loci1. Genetic Map:2. Linkage Map:3. Map Units:4. Cytological Maps:II. Sex ChromosomesA. Chromosomal Basis of Sex B. Sex-Linked Genesa. Sex-Linked DisordersDisorders carried on the X or Y chromosome, although majority are carried by the X chromosome. The Y chromosome doesn’t have a matching gene. It is easier for a male to acquire a sex-linked disorder because they only have one X chromosome while females have two that have to match in order to have a disorder.1. Color Blindness: 2. Duchenne Muscular Dystrophy: recessive gene disorder where muscles can’t repair themselves because of missing dystrophin3. Hemophilia: recessive gene disorder where there is no factor 8 protein, so blood doesn’t clotb. X Inactivation in Females1. Barr Body: the inactive X chromosome in each cell of a female. It is later reactivated in the ovary cells that become ova.III. Errors and ExceptionsA. Alterations of Chromosome Number or Structurea. Alterations of Chromosome Number1. Nondisjunction: a pair of homologous chromosomes do not separate properly during meiosis I or sister chromatid fail to separate in meiosis II 2. Aneuploidy: abnormal chromosome number3. Trisomic: the cell has an extra chromosome (2n+1)4. Monosomic: the cell is missing a chromosome (2n-1)5. Polyploidy: a cell contains more than one set of homologous pairs (3n) or (4n)b. Alterations of Chromosome Structure1. Deletion: removes a chromosomal segment2. Duplication: repeats a chromosomal segment3. Inversion: reverses a segment within a chromosome4. Translocation: moves a segment from one chromosome to another, nonhomologous one. c. Human Disorders1. Down Syndrome: extra chromosome 21 causing mental retardation and other health problems (XXX)2. Turner’s Syndrome: female doesn’t have a second X chromosome, so she will not go through puberty. (XO)3. Klinefelter’s Syndrome: male has an extra X chromosome, so he will be sterile. (XXY)4. Jacob’s Syndrome: male has an extra Y chromosome, he will be sterile and have mental retardation (XYY)5. Triple X: female has an extra X chromosome, normal healthB. Phenotypic Effects1. Genomic Imprinting: genes are expressed in a parent of origin, meaning depending on the parent the chromosome was retrieved determines the physical expression or disease.2. Fragile X Syndrome: abnormal X chromosome, the tip is hanging by a thin thread, which causes mental retardation in both male and femalesC. Extranuclear Genes1. Mitochondria and plastids in plants reproduce by replications by the way of extranuclear DNA found in the organs themselves. They do not follow the Mendelian inheritance belief because their way of distribution does not follow the same rules. The maternal mitochondria is the same in all of its
View Full Document
Unlocking...