BIOL 111 1st Edition Exam 3 Study Guide Before Mendel 1860s ideas about inheritance o Gregor Mendel 1822 1884 the Revolutionary monk o Training in mathematics o Simple system Pea plants True breeding plants Very prolific get lots of offspring grow very quickly have lots of characteristics that are easy to follow If you let the plant self fertilize the characteristics of the plant stay true Study one characteristic at a time Mendel didn t try to study everything at once and used different experiments to study different characteristics Use quantitative analysis determine patterns Counting measuring to get data Experiment 1 o Monohybrid cross two true breeding plants What traits appear in F1 Purple and white flowers the dominant trait is purple and the recessive is white Review P the parents F1 the offspring True breed Hybrid one of each of the traits from the true breeding parents Dominant the trait that appears Recessive the trait that is covered up by the dominant trait o Mendel s simple system True breeding pea plants Study one characteristic at a time Count and determine patterns Experiment 2 o What traits appear in F2 o Repeat with different characteristics o Notice ratio 3 1 Why Realized that the blending hypothesis did not work anymore and decided to make a different model o What is an allele or heritable factor Like sister chromatids except that alleles are different from one another because one is from mom and one is from dad while sister chromatids are exactly identical to each other o Review F2 second generation of species Allele heritable factors that can be passed down form generation to generation Meiosis o o Where are alleles during gamete formation An individual trait has only one allele in gamete formation How to geneticists represent alleles o Dominant trait CAPITAL letter o Recessive trait lower case letter o Use letters to show all possible alleles present in gametes o Punnent square used to predict possible offspring allele combos from parents with known genetic makeup Law of segregation o Following one trait o Allele pairs separate segregate suring gametogenesis and re pair at fertilization o Review Homozygous same alleles AA aa Heterozygous different alleles Aa Phenotype the outward appearance of an individual flower color purple Genotype the actual genetic make up of the individual the alleles AA o F2 ratios Experiment 3 Test Cross o Determine unknown genotype of a dominant phenotype by crossing with recessive homozygote why If you did not cross with the homozygote you would not know whether the unknown was homozygous or heterozygous o Experiment 4 Dihybrid cross follow two traits for two generations o Now following two traits start out with true breeding individuals and wants to find out if two traits are inherited independently dependently o How to alleles segregate Independently or dependently Law of independent assortment o Determine possible gamete alleles for P generation RRYY rryy o Predict genotype and phenotype of F1 Dependent assortment you would get YYRR YyRr YyRr yyrr and would get a phenotypic ratio of 3 1 Independent assortment you would get YYRR YYRr YyRR YyRr YYRr YYrr YyRr Yyrr YyRR YyRr yyRR yyRr YyRr Yyrr yyRr yyrr and the phenotypic ratio is 9 3 3 1 o Following two traits at a time dihybrid cross o Each allele pair segregates independently of other pairs of alleles during gamete formation Sex determination in mammals o Sex chromosomes XY system o Sex linked genes Examples in mammals SRY gene sex determining region of Y chromosomes DAX gene dosage sensitive gene on X chromosome Sex linked traits disorders o Due to gene on a sex chromosome X or Y o Often recessive Female XX carrier if heterozygous or affected by homozygous Male XY hemizygous affected if have gene Ex Color blindness hemophilia o Sex linked traits were one of the original pieces of evidence for genes associating with chromosomes Discovery timeline o 1860s Mendel s laws of inheritance o 1870 1890s physical process of mitosis and meiosis discovered o 1902 Sutton and Boveri propose chromosomal theory of inheritance Medelian genes have specific loci positions on chromosomes Thomas Hunt Morgan early 1900 s o Provided physical evidence for genes associating with chromosome o Used Drosophilia melanogaster Fig 15 3 o Studied sex linked traits o Morgan s correlation a trait eye color correlates with an individual s sex lends support to chromosomal theory of inheritance Genetic variation recombination of genes o Independent assortment recombines unlinked genes Examine figure 15 2 do all of the offspring look like the parents o Independent assortment recombines unlinked genes Use TESTCROSS to study figure 15 UN2 Pg 294 o Crossing over recombines linked genes Figure 15 9 Morgan s experiment 3 TESTCROSS o If TESTCROSS results in Parental type greater than 50 offspring phenotypes Recombinant type much less than 50 offspring phenotypes new combos THEN Linked genes genes located on the same chromosome tend to be inherited together but not always du to crossing over Abnormal chromosome number o Nondisjunction when homologous chromosomes or sister chromatids do NOT separate Aneuploidy offspring with abnormal number of a particular chromosome monosomy trisomy Ex Down syndrome trisomy 21 klinefelter syndrome XXYY turner syndrome XO Polyploidy offspring with more than 2 complete chromosome sets Triploidy 3N tetraploid 4N etc Testing for Genetic Disorders o Identify carriers use in vitro fertilization and screen embryos o Fetal testing Fig 14 18 amniocentesis chorionic villus sampling ultrasound o Newborn screening PKU phenylketonuria treat with special diet
View Full Document
Unlocking...