PowerPoint 프레젠테이션

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1 Application of Statistics in Genetics Chapter 2

2 Section 1. Probability What is Probability? In mathematics, the number is less than 1, it refers to the overall likelihood of an eve nt 又称机率 / 几率 / 或然率 : 在数学上是小于 1 的数, 它是指在总体中某一事件发生的可能性 ( 几率 )

3 Principle P-- a certain thing probability of occurrence, the absolute value of a Q --- a certain thing does not occur, the absolute value of b Event--- Refers to things a certain situation or some sort of test results obtained a+b=total p+q=1 p=a/a+b q=b/a+b

4 Probability Probability number of times an event is expected to happen number of times an event could happen Probability can be expressed a a percentage, a decimal or a fraction eg. 50%, 0.50 or 1/2

5 Fundamental theorem Product Rule ( 乘法定理 ) 两个独立事件同时或相继发生的概率等于各个事件发生的概率的乘积 Two separate events (independent events) occur simultaneously or in succession in all probability is equal to the product of the probability of occurrence P(AB) = P(A) P(B)

6 Sum Rule ( 加法定理 ) 两个互斥事件中某一事件发生的概率是各个事件各自发生的概率之和 Two mutually exclusive events in the probability o f occurrence of an event is the events and of their p robability of occurrence. P(A+B)=P(A)+P(B) Exclusive Event ( 互斥事件 ): In one experiment, a n event occurs, another event is exclusion

7 Probability & genetics Outcome of 1 toss has no impact on the outcome of the next toss probability of tossing heads each ti me? 50% probability making a P gamete eac h time? 50% Pp P p

8 Pedigree Analysis of Human 正常男性婚后未生育死于本病正常女性死于其它病婚配双卵双生携带者 I 1 2 单卵双生 X 连锁隐性基因携带者 II 患者性别不详近亲婚配先证者死产或流产

9 Human eye colour? What is the probability of a child being born with blue eyes?

10 Human eye colour Bb Bb P(BB)=1/3 P(Bb)=2/3 Bb P(b)=2/3x1/2=1/3 P(b)=1/2? P(bb)=1/3x1/2=1/6

11 eg, if an individual in the third generation lacks a widow s peak, but both her pa rents have widow s peaks, then her parents must be heterozygous for that gene

12 The same family tree to trace the distribution of attached earlobes ( 耳垂 ) a dominant allele (F) have free earlobes. Some individuals may be ambiguous, free earlobes could be heterozygou s or homozygous dominant.

13 Dominant Disorders Achondroplasia ( 软骨发育不全 ) type of dwarfism 典型侏儒症 Huntington s disease degenerative disease of the nervous system 神经系统退行性疾病

14 常染色体 -- 软骨发育不全并指显性遗传病 X 染色体 -- 抗维生素 D 佝偻病

15 常染色体 : 白化病苯丙酮尿症先天性聋哑隐性遗传病 X 染色体 : 血友病色盲进行性肌营养不良

16 Characters of AD parents are normal, but carrier asynechia ( 不连续性 ) consanguineous mating raised the frequency of attack. 成骨不全 ; 多发性家族性结肠息肉 ; 亨汀顿舞蹈症

17 鱼鳞癣

18 Characters of AR Cystic Fibrosis strikes 1 /2,500 whites of Europ ean descent Sickle Cell disease, 镰状细胞 ( 贫血 ) 病 strikes 1 1/400 African American.

19 智力低下,60 % 患儿有脑电图异常头发细黄, 皮肤色浅和虹膜淡黄色, 惊厥, 尿有发霉臭味或鼠尿味苯丙酮尿症

20 Polygenic/multifactorial inheitance Multifactors interact with environments Family orientation ( 呈家族倾向 ) Inconsistent with Mendelian laws Frequency about 1%- 10% eg. 无脑儿脊柱裂和其它神经管缺损大多数先天性心脏病癌症高血压冠心病痛风精神分裂症抑郁症及糖尿病等

21 多基因遗传的特点 1. 有家族聚集倾向, 没有明显的孟德尔遗传方式 2. 发病风险与遗传度密切相关 3. 亲缘关系的远近与发病率也有关系 4. 家庭中若有一个以上的成员患病再发风险率增高 5. 病情越严重, 亲属的再发风险率越高 6. 当某疾病在一种性别的发病率高于另一种性别的发病率时, 发病率低的性别其后代再发风险升高 7. 双亲近亲婚配, 子女再发风险率高

22 无脑儿 (anencephalus), 女婴占绝大多数, 胎头缺少头盖骨, 脑髓暴露, 脑部发育极为原始, 不能存活面部尚正常, 但双眼常突出常伴有羊水过多, 致早产 ; 如不伴有羊水过多, 则常发展为过期产垂体及肾上腺发育不良, 故孕妇尿中雌三醇常呈低值 ; 无脑儿脑膜直接暴露于羊水中, 羊水中甲胎蛋白常呈高值

24 Binomial distribution formula Section 2

25 如怎样来处理涉及某种事件组合出现的概率呢? 如 Aa aa 杂交产生两个子裔推算这两个子代具有某种遗传组成的概率. * 两个都是 Aa, 概率是?(1/4) * 两个都是 aa, 概率是?( 1/4 ) * 一个 Aa, 一个 aa 概率是? ( 2/4 )

26 若不管次序先后, 把相应数值积加起来, 以 p 代 Aa;q 代 aa 则有公式 (p+q) 2 =p 2 +2pq+q 2 = (Aa) 2 +2(Aa) (aa)+(aa) 2 从概率分布值看, 恰好是公式的系数

27 二项式公式与通式用于分析两对立事件 ( 非此即彼 ) 在多次试验中每种事件组合发生的概率设 A B 为对立事件,P(A)= p, P(B)= q,n 为估测其事件出现概率的事件数显然 P(A+B)=p + q = 1 r: 在 n 次事件中 A 事件出现的次数 ; n-r: 在 n 次事件中 B 事件出现的次数 ;

28 Represents all of the possibilities for a given set of unorder ed events P = n! x! (n x)! px q n x where p = probability that the unordered number of events will occur n = total number of events x = number of events in one category p = individual probability of x q = individual probability of the other category

29 Tests for goodness of fit: chi-square tests Section 3

30 适合度检验 X 2 的定义 : X 2 = ( 实测值 - 预期值 ) 2 O - E) 2 = 预期值 E 显著水平 : 通常以 5% 为大偏差,95% 为小偏差, 落在 5% 区间为差异显著实测值 Observed, 预计值 Expected

31 3 X 2 测验计算 X 2 值后, 查 X 2 表 ( 表 2-5), 如概率值落在小区间 (5%), 为差异显著, 落在大区间 (95%) 为差异不显著 4 自由度: 观察总算与各项预期值确定以后, 在被考察的项数中能够自由变动的项数一般情况下 : 自由度 (df)= 考察的项目数 -1

33 Eg. 真实遗传紫茎, 缺刻叶植株 (AACC) 与真实遗传的绿茎马铃薯叶植株 (aacc) 杂交 F2 代 : 紫缺 (247); 紫马 (90); 绿缺 (8 3); 绿马 (34) 问: 1) 总共 454 株后中, 四种表型预期数? 2) 进行测验 3) 问这两对基因是否自由组合的?

36 2 x 表差异显著性标准差异极显著性标准 P df 自由度 : 在各项预期值决定后, 实得数中能自由变动的项数 df= n-1( 分离组数 -1)

37 Any Questions?

Microsoft PowerPoint - NCBA_Cattlemens_College_Darrh_B

Microsoft PowerPoint - NCBA_Cattlemens_College_Darrh_B Introduction to Genetics Darrh Bullock University of Kentucky The Model Trait = Genetics + Environment Genetics Additive Predictable effects that get passed from generation to generation Non-Additive Primarily