连锁遗传及染色讲义体作图

P 有色、饱满、非糯 (++ ++ ++ ) × 无色、皱缩、糯性(cc shsh wxwx) F1 有色、饱满、非糯 (+c +sh +wx) × 无色、皱缩、糯性(cc shsh wxwx)
Phenotypes
Genotypes
no. of F2 assembled types
有色、饱满、非糯
亲本 灰身残翅 (male)
×
BB
vg vg
子一代
灰身长翅(female)
黑身长翅 (female)
b
b
Vg Vg
× 黑身残翅(male)
子代配子
B
b
vg
Vg
b
b
vg vg
配子比两两相等
B
B
bb
b
vg Vg vg Vg
vg
测交后代 亲本型83%
Bb vg vg
灰身残翅
41.5%
Bb
Vg vg
灰身长翅
Two-factor crosses (两点测验法)
eg. Maize:
有色C / 无色c
饱满Sh / 凹陷sh
非糯性Wx / 糯性wx
Crosses are set out below:
1. 有色、饱满
(CCShSh) ×
2.
无色、凹
陷(ccshsh)
3. F1 CcShsh
×
4.
无色、凹
陷(ccshsh)
* 发生交换的性母细胞比例为交换值的?倍
4.3 Mapping gene on chromosome
单交换(single cross-overs)：基因间分别发生单个交换 双交换(double cross-overs)：同源染色体上的等位基因间同时 发生两次单交换。
图距：If the recombination frequency is 14%, they have a map distance of 14 map units (图距) between them. 1% recombination is equivalent to 1 map unit. (1%的重组率等于1 个图距)
b
b
Vg Vg
× 黑身残翅 (female)
B
b
vg
Vg
b
b
vg vg
子代配子
B
b
b
vg
Vg 配子比1:1
vg
测交后代
B
b
vg
ຫໍສະໝຸດ Baidu
vg
灰身残翅
b
b
Vg
vg
黑身长翅
表型比1:1
Complete linkage
同源染色体上的基因随其染色体一起进入 到同一配子中去的遗传方式。
4.1.2 雌果蝇的不完全连锁遗传 (incomplete linkage)：
Frequency of cross-overs ={重组配子数(交换型配子数) / 总配子数(交换型+亲本型)}×100% = (No. of recombinant / Total no. of progeny) ×100% = 50% = 0 ~ 50% =0
The closer the two genes are together the less likely it is that a cross-over will take place between them. The frequency of recombinants give an indirect measure of how close the two genes lie to each other.
|----------------20----------|----3.6----|
wx
sh
c
|-------------20------------|
|-----3.6----|----16.4------|
sh
c
wx
3. 非糯性、有色(WxWxCC) × 糯性、无色(wxwxcc)
F1 WxwxCc × 糯性、无色(wxwxcc)
5. C、Sh交换值
重组
3.6%
6. 3.6 cM
2. 糯性、饱满(wxwxShSh) ×非糯性、凹陷(WxWxshsh) F1 WxwxShsh × 糯性、凹陷 (wxwxshsh)
W、Sh交换值20%, 20 cM
|-------------23.6-----------------------|
连锁 - 两个或两个以上等位基因一起从一代传递到下一代的现象。
4.1.1 Complete linkage (完全连锁):
e.g. 雄性果蝇的完全连锁遗传(测交后代表型与亲本完全一致,无新类型产生)：
亲本 灰身残翅 (male)
×
B
B
vg vg
子一代
灰身长翅 (male)
黑身长翅 (female)
精品
连锁遗传及染色体作图
4.1 Law of Linkage (连锁规律)
Linkage is the tendency for alleles of two or more genes to pass from one generation to the next in the same combination. Only genes situated on the same chromosome can show linkage. That means the closer together any two genes lie on the same chromosome the more linkage they are to show linkage and the stronger that linkage will be.
bb vg vg
黑身残翅
b
b
Vg vg
黑身长翅
8.5% 8.5% 41.5% 交换型 17%
Incomplete linkage 同源染色体上的基因既有连锁又有交换的遗传现象 — 连锁互换律 presented in 1910 by Morgan
4.2 Frequency of cross-overs (交换值)
+++
2238
parental
无色、皱缩、糯性
W、C 交换值22%，22cM
两值为什么不完全一致?
Three-factor crosses (三点测验法): These are more accurate than two-factor crosses, in that they identify and utilize many of the double cross-overs that are missed by two-factor cross.