产生变异

This implied that the genetic mutations of HN resulted in antigenic variations of these viruses and the search for new vaccines would be necessary.

这表明， NDV的分子变异已经对NDV的抗原性变异产生了影响，研制新型的疫苗成为必然。

The internal cause includes polarity variation , inbred variation , instability of hybridization and gene mutation . The external cause includes unfitting culture conditions , strain ag ing , unsuitable preservation and infection virus of asexuality propagation .

内因主要包括极性发生变异，自交产生的变异，杂交种性不稳定和基因突变；外因主要包括培养条件不适宜，菌种老化，菌种保藏不当和菌株无性繁殖体感染病毒。

In order to improve the local search ability, after the chiasma operation, simulation anneal mechanism is introduced, and a new aberrance operation is used.

为提高遗传算法的局部搜索能力，在交叉操作后引入模拟退火机制，并采用一种新的变异操作，每次变异产生二个子代，然后根据情况取舍，引入接受相对差的子代的概率，这样可以一定程度上避免陷入局部极值。

After two years continuous self-pollination,the variated specificities of five kinds of variations of maize induced by colchicine were examined and measured.

对秋水仙碱诱发产生的5种玉米变异材料，在自交2年后，进行了变异特性的追踪检测。

Available data on helminth genetic variability have shown that most helminth populations exhibit different levels of genetic variation resulting mainly from the pattern of life cycle,geographical distribution and parasite-host interaction,and several hypotheses have been proposed to explain the genetic variation.

应用这些遗传标记的研究表明，大多数寄生蠕虫群体遗传结构有不同水平的变异，这些变异的产生主要与寄生虫的生活史和群体生态、宿主的地理分布和环境等因素有关，并因此提出了有关遗传变异的一些假说。

We studied the optimum medium and hormone combination of callus induction from cotyledons, subculture of callus, shoot regeneration from callus, shoot-extension induction, root induction and identified the chromosome number of the plantlet. The results showed that: MS+2,4-D 2.0mg/L+KT 0.5mg/L, MS＋2,4-D 2.5mg/L＋KT 0.5mg/L, MS+2,4-D 0+KT 1.0mg/L, MS+KT 0.5 mg/L and basal MS medium. One plantlet among twenty two was determined as a tetraploidy based on the plant morphology, observation of the leaf stoma and chromosome number of the root, other two plantlets represented morphological variation.

结果表明，诱导章丘大葱子叶产生愈伤组织、愈伤组织的继代培养、愈伤组织芽分化、芽点的伸长及诱导生根的最佳培养基及激素配比分别为：MS+2，4-D 2.0mg/L+KT 0.5mg/L、MS＋2，4-D 2.5mg/L＋KT 0.5mg/L、MS+2，4-D 0+KT 1.0mg/L、MS+KT 0.5mg/L和MS基本培养基；试管苗经驯化移栽后，共有22株成活，成活率为92%，对成活的再生植株进行形态学、叶片气孔及根尖染色体鉴定表明，共有3株发生变异，其中2株为外部形态上的变异，而另一株为染色体的加倍变异。

The difference of the elevation in altitude and latitude bring about the difference of the temperature and light duration, and the integrated effect by heat and humidity was important to the geographical variation of the traits in stem growth of Akebia.

结果表明：三叶木通地理变异的基本模式是以海拔垂直梯度变异为主，纬向渐变为辅；海拔及纬度差异产生了温度和光照差异，水热因子的综合选择作用是三叶木通茎藤生长性状地理变异的重要原因，其中温度和光照是主导因子。

According to the clock that ticks off the increase in diversity of the DNA of a group of animals due to the accumulation of random mutations, this "population bottleneck" occurred at the beginning of the Younger Dryas.

通过统计出这群动物由于随机变异的积累所产生的DNA变异的情况，从而推算出种群变异的时间，发现这种&种群数瓶颈&恰恰发生在新仙女木期的开始阶段。

Fifty-five lines with different Wx genes from the DH population of Yangmai 10/Waxy C, and 12 waxy wheat varieties derived from the crosses or backcrosses of Yangmai 9 as no-waxy parent or recurrent parent with different waxy wheat varieties were used to study the effects of Wx genes on percentage of vitreous kernel. The grain protein content of 12 waxy wheat varieties with floury endosperm from different crosses was also tested.

为了明确Wx基因变异与小麦籽粒胚乳的关系，以玉米花粉诱导扬麦10号（角质胚乳品种，非糯小麦）与糯质供体Waxy C杂种F1产生的不同Wx基因变异类型的55个双单倍体系以及以扬麦9号与不同糯质供体亲本杂交、回交育成的12个糯小麦品系为材料，研究了Wx基因变异对籽粒胚乳质地的影响，同时测定了12个不同来源的粉质胚乳糯小麦籽粒蛋白质含量。

Compared with the exchange and mutation operation in genetic algorithm ,crossover operation becomes helpless when adaptive value of most individules in demes have little difference.The algorithm falls into local solution and can't be solved by exchange. Although mutation can make it shake off local convergence and jump out of local solution, denteric mutation may destroy the produced module that is constructive to form the optimal solution.

相比遗传算法中的交换和变异操作，当种群的多数个体适应值相差不大时交叉操作就显得无能为力，算法陷入局部解而不能由交换解决，突然变异能够使之摆脱局部收敛而跃出局部解，但是后期的变异可能破坏已产生的对形成最优解有建设性作用的模块。

With Death guitarist Schuldiner adopting vocal duties, the band made a major impact on the scene.

随着死亡的吉他手Schuldiner接受主唱的职务，乐队在现实中树立了重要的影响。

But he could still end up breakfasting on Swiss-government issue muesli because all six are accused of nicking around 45 million pounds they should have paid to FIFA.

不过他最后仍有可能沦为瑞士政府&议事餐桌&上的一道早餐，因为这所有六个人都被指控把本应支付给国际足联的大约4500万英镑骗了个精光。