发布时间 : 星期三 文章遗传学期末考试复习资料 - 图文更新完毕开始阅读
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 ? 1. Introduction.
? 2. Three laws of genetics.
? 3. The chromosome theory of inheritance. ? 4. The mapping and analysis of genomes. ? 5. Genetics of genomes. ? 6. Quantitative genetics. ? 7. Population genetics.
? 8. Gene functions in molecular level. ? 9. Extranuclear inheritance.
? 10. Gene mutation and epigenetic variation. ? 11. Genetic recombination and transposon. ? 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 varieties
Peas are small, easy to grow, short generation time Peas 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 + Environment
Crop 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
* Phenotype can be determined by treating drops of blood with antisera which react with the A or B sugar groups
? Mendel believed that all units of inheritance are passed on to offspring unchanged.
Unstable alleles are an important exception to this rule.
? The environment sometimes affects the expression of a gene, changing phenotypes ? * Example: Himalayan rabbit (喜玛拉雅兔)
? * Coat color in a warm environment (above 30 deg C) is white
? * At 25 deg C colder parts of the animal (ears, tip of nose, feet) are black ? * Melanin-producing gene is turned on in cells at low temperature ? A Character May Be Determined by More Than One Gene ? A good example is the feather color of budgies(相思鹦鹉)
? * Color caused by 2 genes: Y gene produces yellow pigment in outer feather; B gene
produces bluish pigment in core of feather ? * YYbb or Yybb -> yellow bird ? * yyBB or yyBb -> blue bird
? * YYBB, YyBB, YYBb or YyBb -> green bird ? * yybb -> white bird
? Sex Related Genetic effects ? An example of this is gout（痛风）, a disease that causes painfully inflamed joints. If the
gene is present, men are nearly eight times more likely than women to have severe symptoms.
? Some genes are known to have a different effect depending on the gender of the
parent from whom they are inherited. This phenomenon is referred to as genome imprinting (基因组印迹)or genetic imprinting. Apparently, diabetes, psoriasis（牛皮癣）, and some rare genetically inherited diseases, such as a form of mental retardation known as Angelman syndrome, can follow this inheritance pattern
3.Chromosome
“theory” of inheritance
? Somatic cell = any cell other than sperm or egg. Human somatic cells have 46
chromosomes ? Homologous chromosomes = chromosomes that have same centromere position, same
genetic loci, and same length. ? ? ? ?
How, then, are homologous chromosomes different from one another?
Genotypic sex determination system:与染色体或基因型有关的性别决定系统。
Enviromental or phenotype sex determination system: 与环境因素有关的性别决定系统。
? Sex chromosomes: 与性别决定有明显而直接关系的染色体。 ? Autosomes：性染色体以外的所有染色体。
?
? 果蝇的性别与Y染色体的存在无关，是由X染色体的数目和常染色体的套数之比例
(性指数)决定的，这种方式叫性染色体-常染色体平衡决定系统。（X Chromosome-autosome balance system of sex determination)
? 而对于人，则与比例无关，只要有Y就是男性。性染色体数目的增减，常使性腺发
育不全，失去生育能力。少一个性染色体的影响比多一个的影响要大些。 为什么Y染色体对男性发育重要？
人及哺乳动物Y染色体上有编码睾丸发育的决定因子（testis-determining factor, TDF）,它位于Y染色体的短臂上，编码223个氨基酸组成的多肽，称为SRY（sex-determining factor）基因。
巴氏小体
由于这种染色质小体与性别及染色体数目有关，所以称为性染色质体（sex-chromatin body），又名巴氏小体（Barr body）。巴氏小体是一种高度浓缩的、惰性的、异染色质化的小体，它就是失活的X染色体。 ?
ZW型性别决定 鸟类（包括家禽）、家蚕、两栖类（如青蛙等）、爬行类（蛇、鳄、乌龟）等 环境性别决定系统