Edited with the trial version of Foxit Advanced PDF Editor To remove this notice visit www foxitsoftware com shopping BIOL 1543 1st Edition Lecture 12 Outline of Last Lecture I A review of mitosis II Chromosomes occur in homologous pairs III Gametes only have one set of chromosomes IV Meiosis V Meiosis I VI Meiosis II VII The steps of meiosis VIII A comparison of mitosis and meiosis IX Crossing over X How crossing over increases genetic variation XI ALTERATIONS OF CHROMOSOME NUMBER AND STRUCTURE XII Down syndrome XIII Abnormal numbers of sex chromosomes XIV Human sex chromosome abnormalities Outline of Current Lecture I Purebreeds vs Mutts II Genetics the study of heredity III Law of Segregation IV Alleles and chromosomes V Law of Independent Assortment 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 VI The chromosomal basis of Mendel s laws VII Independent assortment VIII A testcross can determine unknown genotypes IX Human Traits X Dominant Disorders XI Biotechnology reproduction XII Ethical Considerations XIII VARIATIONS ON MENDEL S LAWS XIV Incomplete dominance results in intermediate phenotypes XV Codominance XVI Blood type XVII Pleiotropic genes and polygenic traits XVIII Environmental effects on phenotypes XIX Linked Genes XX Chromosomes and sex determination XXI Sex linked genes XXII Sex linked disorders Current Lecture I Purebreeds vs Mutts a purebreeds are more predictable II Genetics the study of heredity Petal a Experimental genetics began with Gregor Mendel s experiments with pea plants i done around the Civil war b Mendel crossed bred pea plants Stamen Carpel that differed in certain characteristics and traced traits from generation to generation i used pea plants because easy to grow easy to distinguish the different varieties and very easy to have strict control over fertilization III Law of Segregation a Mendel hypothesized that there are alternative forms of genes the units that determine heritable traits b He figured this out in 1866 c Mendel s law of segregation describes the inheritance of a single characteristic i Mendel deduced that an organism has two genes alleles for each inherited characteristic 1 true breeding parents will always produce their color when bred 2 filial F1 generation son and F2 generation ii called a monohybrid cross when dealing with only one characteristic d For each characteristic an organism inherits two alleles one from each parent P generation true breeding parents Purple flowers White flowers F1 generation All plants have purple flowers Fertilization among F1 plants F1 F1 F2 generation 3 of plants 4 1 of plants 4 have purple flowers have white flowers e If the two alleles of an inherited pair differ then one determines the organism s appearance and is called the dominant allele f The other allele has no noticeable effect on the organism s appearance and is called the recessive allele g Mendel s law of segregation predicts that allele pairs separate from each other during the production of gametes i used a punnet square to show the outcomes of the two parents called running the punnet square IV Alleles and chromosomes a Homologous chromosomes bear the two alleles for each characteristic i Alternative forms of a gene reside at the same locus on homologous chromosomes b Must know the terms i heterozygote Gg ii Homozygote dominant GG iii Homozygote recessive gg Gene loci P P Genotype PP Homozygous for the dominant allele Dominant allele a B a b Recessive allele aa Bb Homozygous Heterozygous for the recessive allele V Law of Independent Assortment a The law of independent assortment is revealed by tracking two characteristics at once dihybrid cross i By looking at two characteristics at once Mendel tried to determine how two characteristics were inherited ii Mendel s law of independent assortment states that alleles of a pair segregate independently of other allele pairs during gamete formation VI The chromosomal basis of Mendel s laws a Genes are located on chromosomes whose behavior during meiosis and fertilization accounts for inheritance patterns i If there are 4 gamete possibilities 4 gamete punnet square there will always be the outcome of 9 3 3 1 VII Independent assortment a Di hybrid cross b PRA progressive retinal atrophy blindness VIII A testcross can determine unknown genotypes a The offspring of a testcross a mating between an individual of unknown genotype and a homozygous recessive individual can reveal the unknown s genotype Testcross Genotypes bb B Two possibilities for the black dog BB or Bb Gametes B b Offspring Bb All black B b b Bb bb 1 black 1 chocolate b Mendel s laws reflect the rules of probability i Inheritance follows the rules of probability c Rule of multiplication a compound event more than one possibility is the product of the separate probabilities multiply each possibility together IX Human traits a The inheritance of many human traits follows Mendel s laws b Sometimes these are disorders i Deafness is recessive 1 A carrier is someone who is heterozygote for a recessive gene that predisposes for a hereditary condition c Family pedigrees can be used to determine individual genotypes X Dominant Disorders a Some human genetic disorders are dominant i Achondroplasia dwarfism homozygote dominant would lead to death Mini Me has this and he is heterozygote ii Huntington s disease A degeneration of the nervous system 1 Not immediately harmful Doesn t appear till about middle age and then it is fatal Will die generally 10 20 years after diagnosis b Some disorders are fatal others are not immediately harmful Pedigree XI Biotechnology reproduction a New technologies can provide insight for reproductive decisions i Identifying Carriers 1 For an increasing number of genetic disorders tests are available that can identify carriers of genetic disorders ii Fetal Testing 1 Fetal cells can be tested for genetic abnormalities a Amniocentesis will remove some fluid from the uterus to test testing genotype for trisomy 21 b CVS Choriojicdillous sampling testing the placenta iii Fetal Imaging 1 Ultrasound imaging uses sound waves to produce a picture of the fetus testing phenotype iv Newborn Screening 1 Some genetic disorders can be detected at birth by simple tests now routinely performed in most hospitals in the U S a phenylketonuria can be controlled with a certain diet caused by an inability to break down