遗传复习资料（白痴粗略版，参考要慎重，呵呵！另外没按老师讲课的顺序）Lecture Contents v 1. Introduction. v 2. Three laws of genetics. v 3. The chromosome theory of inheritance.v 4. The mapping and analysis of genomes.v 5. Genetics of genomes. v 6. Quantitative genetics. v 7. Population genetics.v 8. Gene functions in molecular level.v 9. Extranuclear inheritance.v 10. Gene mutation and epigenetic variation.v 11. Genetic recombination and transposon.v 12. Developmental genetics（待定）.2.Three laws of genetics.基因的分离定律，自由组合定律，连锁与互换定律Segregation An individual inherits a unit of information (allele) about a trait from each parent During gamete formation, the alleles segregate from each other Independent assortment Traits are not inherited together In forming the gametes, the “Factors” for any two traits assort independently from one another Mendel concluded that the two “units” for the first trait were to be assorted into gametes independently of the two “units” for the other trait Members of each pair of homologous chromosomes are sorted into gametes at random during meiosis 连锁与互换定律：处在同一染色体上的两个或两个以上基因遗传时，联合在一起的频率大于重新组合的频率；在配子形成的过程中，同源染色体的非姊妹染色单体间发生局部交换的结果导致重组类型的产生。What are the advantages of peas?Large # of pea varietiesPeas are small, easy to grow, short generation timePeas can self-fertilize; bisexual Dominance显性=the ability of one allele to express its phenotype at the expense of an alternate allele; the major form of interaction between alleles; generally the dominant allele will make a gene product that the recessive can not; therefore the dominant allele will express itself whenever it is present Recessive隐性= an allele whose expression is suppressed in the presence of a dominant allele; the phenotype that disappears in the F1 generation from the cross of two pure lines and reappears in the F2 generation Genotype = the genes of an organism; for one specific trait we use two letters to represent the genotype. A capital letter represents the dominant form of a gene (allele), and a lowercase letter is the abbreviation for the recessive form of the gene (allele). Phenotype = the physical appearance of a trait in an organism Allele-one alternative form of a given gene pair; tall and dwarf are the alleles for the height of a pea plant; more than two alleles can exist for any specific gene, but only two of them will be found within any individual Allelic pair等位基因对 = a combination of two alleles Homozygote = an individual which contains only one allele at the allelic pair; for example DD is homozygous dominant and dd is homozygous recessive; pure lines are homozygous for the gene of interest Heterozygote = an individual that contains two different alleles at the allelic pair; for example the Dd heterozygote Backcross = the cross of an F1 hybrid to one of the homozygous parents; for pea plant height the cross would be Dd x DD or Dd x dd; most often, though a backcross is a cross to a fully recessive parent Testcross = the cross of any individual to a homozygous recessive parent; used to determine if the individual is homozygous dominant or heterozygous Monohybrid 单因子杂种= the offspring of two parents that are homozygous for alternate alleles of a gene Monohybrid cross = cross between parents that differ at a single allelic pair (usually AA x aa) sex-linked inheritance伴性遗传Exceptions to Mendelian Genetics Phenotype = Genotype + EnvironmentCrop Yield = Genotype+ Minerals+ Water+ Light- Pests etc.Human Skin Color = Genotype+ Sun (UV) Exposure- Aging Factors All of the characters studied by Mendel had traits that were dominant or recessive * For many characters the 2 alleles give a blended result * Example: flower color in snapdragons(金鱼草) * Blending of this sort is called incomplete dominance（不完全显性） * In another type of blending both alleles seem to assert their whole effect; example- blood group antigens (see multiple alleles section below); this is called codominance（共显性） * Dominance may depend upon which function of the gene is monitored: Example sickle cell anemia(镰刀型贫血症) gene * Sickle cell gene acts like a recessive in producing anemia * Hemoglobin（血色素） mutation, causes hemoglobin to form crystals, damaging red blood cells * AA = normal (A is normal hemoglobin allele) * AS = heterozygous, relatively normal (no anemia) * SS = homozygous for sickle gene, causes severe anemia * If you look at the amount of hemoglobin produced the alleles look like they are codominant * AS person produces 50% hemoglobin A, 50% hemoglobin S Multiple Alleles Example: ABO blood groups in humans* 3 alleles: A, B, O * A & B dominant over O * A & B codominant to each other * Type O produces no sugar antigens * 6 genotypes and 4 phenotypes