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1.
应用“连锁与互换规律”解题 ,是高中生物遗传学的难点 ,许多学生面对此类习题往往束手无策。为此 ,介绍一法 ,供同行参考。应用此法所要解决的问题 ,常常是“已知测交后代的类型 (基因型 )及其比例 (个体数 ) ,要求确定被测个体(一般是 3对等位基因 )的基因位置”。解题的步骤是 :( 1 )从测交后代的基因型中 ,依次减去测交亲本产生的仅含有隐性基因的配子基因型 ,剩下的即为被测个体产生的配子基因型 (一般是 3个基因 )。( 2 )两两分析 ,确定被测个体的基因位置。即对被测个体产生的配子 (剩下部分 ) ,作两对等位基因分析。若出现 4种基因… 相似文献
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狭义的测交指杂种第一代与隐性亲本的杂交,而实际上,测交可以泛指隐性个体与各种相应基因型个体的杂交,在中学生物遗传规律的教学中,测交可谓点睛之笔,不可轻描淡写,泛泛而论。 一、测交的性质 1.测交后代表现型的种类及比例,基因型的种类及比例与被测交者产生的配子的种类及比例均相同。致使“三个相同”的原因是:隐性亲本产生的配子中,不带有显性基因,从而对被测交者配子中基因的表达没有遮盖作用。 2.测交后代表现型已知,则可确定其基因型。原因是:测交后代的1/2基因来自于隐性亲本,如果表现出隐性性状,当然是隐性纯合体,如果表现出显性性状,则一定是杂合体。 二、测交的应用 1.测交可测知生物未知的基因型 生物的基因型、配子的基因型,是无法直接观察到的,能肉眼看到的只是生物的表现型,测交却能使我们透过测交后代的表现型,“看”到测交生物产生的配子的种类和比例,谁知生物未知的基因型。 例:在蕃茄中,缺刻叶和马铃薯叶是一对相对性状,显性基因B控制缺刻叶,基因型bb是马铃薯叶。紫茎和绿茎是另一对相对性状,显性基因A控制紫茎,基因型aa是绿茎。现有表现型均为紫茎缺刻叶的三个蕃茄品种, 相似文献
3.
2009年9月,省普通话培训测试中心率先在省里开展了计算机辅助普通话水平测试(以下简称机测)试点。目前为止,共有1000余名应试人参加了机测,笔者对应试人上机操作过程中出现的情况和问题进行了归类分析,并提出解决方案,以利机测在各市(州、地)更快更好地开展和普及。 相似文献
4.
文章着重研究了计算机辅助普通话水平测试后(以下简称"机测")出现的新特点与新情况,通过分析传统的测试员在现场评分(以下简称"人测")与机测在应试状态、应试心理等方面的不同及其对应试者产生的影响来探究机测后培训的内容、方法和策略,以期使应试者掌握机测的要领,切实提高应试者的普通话水平。 相似文献
5.
孟德尔通过8年的豌豆杂交实验,发现了基因的分离定律和自由组合定律.在基因的分离定律中,具有一对相对性状的纯合亲本杂交,F2表现出3:1的分离比,F1测交后代的比例为1∶1;在基因的自由组合定律中,具有两对相对性状的纯合亲本杂交,F2表现出9∶3∶3∶1的分离比,F1测交后代的比例为1∶1∶1∶1. 相似文献
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掌握准确快速解决遗传学自由组合定律相关问题的技巧对教师和考生来说是十分重要的,"合并同类项"在巧推自由组合规律特殊比值中是一种好方法.
1遵循自由组合定律的2对相对性状在后代中表现型以及测交结果的常规推导
位于两对同源染色体上,控制两对完全显性性状的等位基因,如甲性状(A、a)、乙性状(B、b).若亲本基因型分别为AABB、aabb(或为AAbb,aaBB),则F1基因型为AaBb;F1自交,则F2中表现型及其比例为9A_B_(甲显乙显)∶3A_bb(甲显乙隐)∶3aaB_(甲隐乙显)∶1aabb(甲隐乙隐),即9∶3∶3∶1;F1测交,即AaBb×aabb,则后代表现型及其比例为1Aabb(甲显乙隐)∶1AaBb(甲显乙显)∶1aaBb(甲隐乙显)∶1aabb(甲隐乙隐),即1∶1∶1∶1. 相似文献
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现在还未见到较为理想的凸极机等效电路。本文应用电路理论和凸极机的双反应理论,构造了两种等效电路,这对凸极机的理论研究和应用将提供必要的基础。1.凸极机等效电路的 CGVH 形式(见图1)凸极机的电势平衡方程为(?)(1)其中,(?)分别为直轴电流相量和交轴电流相量;X_d、X_q 分别为直轴同步电抗和交轴同步电抗。 相似文献
9.
关于基因分离定律和基因的自由组合定律,孟德尔在对其进行验证的时候都采用了测交实验,通过测交试验来看F1的基因型。孟德尔为什么用测交试验呢?以基因分离定律试验为例。基因分离定律指的是一对等位基因遗传的情况。F1为Dd,如果孟德尔采用自交来验证F1的基因型可不可以呢?这不 相似文献
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在近几年高考理综全国卷的生物试题中,经常结合减数分裂、生物图表、伴性遗传、生物育种等知识综合考查考生的能力。对遗传基本规律的考查,近几年高考主要集中在:(1)测交、基因型、表现型等基本概念的理解与运用;(2)根据亲(子)代的基因型或表现型比例推子(亲)代的基因型或表现型比例;(3)遗传系谱图的判定、亲子代基因型的推断及遗传概率的计算。其中遗传图谱分析是高考命题的热点,考查的知识点主要集中在以下几个方面:一是显性或隐性性状遗传的判定;二是常染色体或性染色体遗传的判定;三是亲子代表现型或基因型的确定;四是遗传病发生几率的分析及预测。 相似文献
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为了将玉米A型胞质不育准确归群,从分析A型不育系育性基因型入手,结合恢复性的遗传和小斑病的自然感染进行综合研究。采用启行设计的A型与T、S、C三类群的不育系(保持系)的互测杂交试验,初证出A型不育系的育性基因位点及对数;并用多型恢复进行辅助签定;14个自交系与A型不育系的杂交F_2代育性反应分别呈3∶1和9∶7,符合T型恢复性的遗传规律;最后再结合A型细胞质受小斑病感染的事实,初步将A型归入T群,试验结果表明,通过明确育性基因互位点上,有助于分析特定自交系测交育性反应的疑异和胞质不育的分类。 相似文献
12.
An excellent airfoil with a high lift-to-drag ratio may decrease oil consumption and enhance the voyage. Based on NACA 0012, an improved airfoil is explored in this paper. The class/shape function transformation has been proved to be a good method for airfoil parameterization, and in this paper it is modified to improve imitation accuracy. The computational fluid dynamics method is applied to obtain numerically the aerodynamic parameters of the parameterized airfoil, and the result is proved credible by comparison with available experimental data in the open literature. A polynomial-based response surface model and the uniform Latin hypercube sampling method are employed to decrease computational cost. Finally, the nonlinear programming by quadratic Lagrangian method is utilized to modify the multi-island genetic algorithm, which has an improved optimization effect than the method used on its own. The obtained result shows that the modified class/shape function transformation method produces a better imitation of an airfoil in the nose and tail regions than the original method, and that it will satisfy the tolerance zone of the model in a wind tunnel. The response surface model based on the uniform Latin hypercube sampling method gives an accurate prediction of the lift-to-drag ratio with changes in the design variables. The numerical result of the flow around the airfoil shows reasonable agreement with the experimental data graphically and quantitatively. Ultimately, an airfoil with better capacity than the original one is acquired using the multi-island genetic algorithm based nonlinear programming by quadratic Lagrangian optimization method. The pressure contours and lift-to-drag ratio along with the attack angle have been compared with those of the original airfoil, and the results demonstrate the strength of the optimized airfoil. The process for exploring an improved airfoil through parameterization to optimization is worth referencing in future work. 相似文献
13.
Previous twin studies of reading disability employed a comparison of concordance rates in identical and fraternal twin pairs
as a test for genetic etiology. Recently, a statistically more powerful multiple regression analysis of twin data has been
formulated to assess the importance of genetic factors in the development of reading difficulties. Application of this analysis
to twin data from the Colorado Reading Project yields definitive evidence for a genetic etiology. Results from this study
suggest that approximately 40 percent of the deficit observed in the disabled readers is due to genetic factors, 35 percent
is due to environmental influences shared by members of twin pairs, and about 25 percent is the result of environmental factors
unique to the individual and/or error variance.
This work was supported in part by a program project grant from the NICHD (HD-11681). 相似文献
14.
Despite cognitive neuroscience's emphasis on the modularity of cognitive processes, multivariate genetic research indicates that the same genetic factors largely affect diverse cognitive abilities, at least from middle childhood onward. We explored this issue for verbal and nonverbal cognitive development in infancy in a study of 1,937 pairs of same-sex 2-year-old twins born in England and Wales in 1994. The twins were assessed by having their parents use a measure of productive vocabulary (the MacArthur Communicative Development Inventory) and a novel measure of nonverbal cognitive abilities (Parent Report of Children's Ability). Verbal and nonverbal development correlated .42. A multivariate genetic analysis indicated that genetic factors were responsible for less than half of this phenotypic correlation. Moreover, the genetic correlation between verbal and nonverbal abilities was only .30, which indicates that genetic effects on verbal and nonverbal abilities are largely independent in infancy. These multivariate genetic results suggest that genetic effects on cognitive abilities are modular early in development and then become increasingly molar. The implications of this result for theories of cognitive development are discussed. 相似文献
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以合成具有生物活性的配合物为目的,首次合成了苊醌缩氨基硫脲Pt(II)配合物,通过元素分析、红外光谱、紫外光谱和热重差热分析等对配合物进行了结构表征,结果表明配合物为1:1型的配合物,配体配位过程中N-H上质子脱去,以ONS三齿螯合形式与Pt(II)配位。 相似文献
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采用Rietveld全谱拟合的方法对TiO2粉末中锐钛矿和金红石进行定量分析,通过标准样品数据和计算结果进行比较,对该方法的准确性、重复性以及普适性分析,计算结果与标准样品数据符合良好.该方法具有快速准确、成本低、可重复的特点,在高纯度矿物产品工业中将具有广阔的应用前景. 相似文献
18.
遗传算法在斜齿圆柱齿轮传动优化设计中的应用 总被引：1，自引：0，他引：1
遗传算法是一种模拟生命进化机制的搜索和优化方法，其全局优化和隐含并行性使得遗传算法适合求解大规模的复杂优化问题。该文在介绍遗传算法的基础上，系统论述了遗传算法在斜齿圆柱齿轮传动优化设计中的应用。经实例分析与计算，得到了较为理想的设计结果。通过与传统优化方法的比较，说明遗传算法在机械传动优化设计方面，具有广泛的应用前景。 相似文献
19.
为了提高直线感应电机的力能指标,提出一种新型自适应遗传算法,并对直线感应电机进行了优化设计.采用佳点集理论对遗传算法的初始化种群进行均匀设计,提高了遗传算法的优化效率.同时利用sigmoid函数改进了交叉概率和变异概率,使交叉率和变异率按照个体的适应度在平均适应度和最大适应度之间随sigmoid曲线进行非线性调整.在分析直线感应电机与旋转电机物理结构差异的基础上,得到考虑边端效应的直线感应电机的稳态性能,并给出直线感应电机力能指标的优化模型.通过对优化后的设计方案与原设计方案的比较发现:直线感应电机的力能指标显著提高,验证了方法的有效性. 相似文献
20.
《The Journal of educational research》2012,105(10):464-465
AbstractAn observation scale to measure behavior of teachers was constructed based on a Skinnerian framework of learning:: that pupils learn when their responses to the curriculum are promptly and consistently reinforced. Four categories of behavior were observed for five-minute periods for each of four teachers In preschool nurseries for underprivileged children. The observation categories are; (1) information giving; (2) response elicitation; (3) feedback and (4) teacher control. An analysis of variance of the results showed significant differences In the behavior of the teachers according to these categories. The most interesting result was the significant difference between teachers with respect to the ratio of feedback to response elicitation. According to Skinnerian theory, the larger this ratio, the greater is the likelihood of learning. This hypothesis could be tested by relating the ratio to measures of pupils' achievement. 相似文献