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遗传学上,最小群体数是指杂交后代各性状都能得以充分表现的后代群体最小数目。它是子代性状分离比之和的具体体现,而后者又反映了亲本配子的组合方式。因此,利用最小群体数,可以推测亲本产生配子的种类,进而结合亲本性状,推知其基因型。这种推断基因型的方法,称为最小群体法。 我在运用最小群体法,推断生物基因型的习题教学中,取得了良好的效果。现对其具体使用步骤归纳如下： （１）由亲本性状,写出基因组成。 （２）依据子代性状分离比,求出最小群体数。如果给出的子代是实得个体数,应先约简,再求最小群体数。 （３）利用最… 相似文献
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性别决定一般是指雌雄异体的生物决定性别的方式。生物性别主要是由性染色体决定的。性染色体的类型，在生物界中普遍存在两种：XY型和ZW型。譬如，属于XY型的生物，雌性的性染色体为XX，产生的卵细胞含X染色体；雄性的性染色体为XY，产生的精子含X染色体或Y染色体，两者比例相等。且与卵细胞结合的机会均等，故后代雌雄比例相当。那么， 相似文献
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哺乳动物在自然受精的情况下．后代性别为雄性和雌性的几率约各占50％。性别控制的关键就是将X精子与Y精子分离开来，然后进行体外受精或人工受精，这样就能有选择地生产出预期性别的动物。 相似文献
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<正>1题目火鸡的性别决定方式是ZW型(♀ZW,♂ZZ)。曾有人发现少数雌火鸡(ZW)的卵细胞未与精子结合,也可以发育成二倍体后代。遗传学家推测,该现象产生的原因可能是:卵细胞与同时产生的3个极体 相似文献
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自由组合规律是高中生物的重点和难点内容之一，试题难度大，题型多，计算复杂，但也有一定规律可循。a．个体产生的配子种数。２n（n代表等位基因的对数）。例如：基因型为AaB－bCcDdEE的个体产生的配子种数为２４。b．结合方式数：雌雄配子种数的乘积。例如：AaBbCcDdEE×aaBBCcDdEe，结合方式为：２４×２３＝２７，即１２８种。c．子代表现型种数：两亲本各对性状分别相交，产生表现型种数的乘积。例如：AaBbCcDdEE×aaBBCcDdEe。Aa×aa，子代表现型为２种；Bb×BB，子代表现型为１种；Cc×Cc，子代表现型为２种；Dd×Dd… 相似文献
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贵刊1996年第八期上，刊出王柏龄老师的一文中说：加深了“对生男生女取决于父方”的认识；在其它有关杂志上也有所见；不少中学生物教师在上课时，对XY型性别决定的分析时，也有同说。我认为生男生女应由夫妇双方共同决定，取决于男方的说法是不妥当的。理由是：第一，从性别遗传的角度看，男方可以提供含有X染色体的精子，也可以提供含有Y染色体的精子，且比例大致相等。至于哪一种精子与卵细胞结合是完全随机的，男方并不能主观上控制哪种精子与卵细胞受精，从这个角度看．后代中生男生女的机会就应均等。因此，那种“生男生女取决于男… 相似文献
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文章在论述风险投资运行特点的基础上,对风险投资运作时产生的委托代理问题及其风险进行了分析,在风险投资激励机制和风险企业家薪酬激励等方面做了一定的探讨和研究。 相似文献
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Christopher Wilson 《Learning & behavior》1988,16(1):83-88
A series of experiments was carried out to investigate the ability of different types of stimulation to induce or intensify the “transport response” in 15-day-old rat pups when an initial stimulus, a pinch to the nape of the neck, produced either no transport response or only a very weak response. Rat pups given supplemental tactile stimulation, in the form of either an airpuff to the ventrum of a pinch to the tail, showed consistently stronger response intensities than when given only a pinch to the nape of the neck. Visual and auditory stimuli produced no increment in response intensities over those with only a dorsal pinch. Two additional experiments were carried out. The first investigated the ability of a puff of mist from an atomizer to induce a transport response in rats too old to show a strong response. The second investigated the induction of the transport response with supplemental stimulation in 19-day-old pups given haloperidol. Results suggest a nondopaminergic system subserving the response facilitation seen with supplemental tactile stimulation. 相似文献
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为了研究“红花末”色素的理化特性及食用安全性,采用光谱法分析其吸收图谱及光稳定性和热稳定性,并利用小鼠急性毒性试验、小鼠精子畸变试验等方法进行毒理学研究．结果表明,“红花末”色素溶液在200~800 nm有5个吸收峰,可见区最大吸收峰为540 nm．色素光稳定性较差,热稳定性较好．急性毒性试验表明,“红花末”色素对小鼠的LD50值为1259 mg/kg＆#183;bw,属于低毒级;遗传毒性试验表明：小鼠精子畸变率为8.38%~12.26%,明显高于对照组（0.54%,p＆lt;0.05）．“红花末”色素稳定性较好,属于低毒级,具有一定的致突变性,长期食用可能会对生殖系统产生一定的影响. 相似文献
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李海生 《河北北方学院学报(医学版)》1999,(2)
实验在20只氨基酸乙酯麻醉的成年家兔上进行,观察电刺激面神经核背内侧区(DMNF)和腹内侧区(VMNF)对肾交感神经呼吸节律性放电的影响。结果表明:1.电刺激DMNF时膈肌肌电活动持续增强,出现长吸效应;肾交感神经呼吸节律性放电活动明显抑制。2 电刺激VMNF时膈肌肌电活动完全消失,出现长呼效应;肾交感神经呼吸节律性放电呈连续增频增幅反应。结果提示:DMNF和VMNF可能与延髓交感中枢之间存在某种神经联系,呼吸中枢活动的改变能对内脏活动产生影响。 相似文献
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First-grade males performed a 30-min visual vigilance task under 5 conditions of auditory background stimulation. The 5 conditions consisted of (1) continuous conversation, in which subjects listened to a tape of conversation spliced so that there were no intervals of silence lasting longer than 3 sec; (2) continuous reverse, in which subjects heard the continuous conversation tape played in reverse; (3) intermittent conversation, in which subjects heard alternating segments of conversation and silence; (4) intermittent reverse, in which subjects heard alternating segments of reverse conversation and silence; and (5) silence control. Compared with silence or continuous stimulation, intermittent stimulation produced better detection regardless of whether or not it was meaningful. High achievers made more correct detections than low achievers, but only in the second and third time periods. Few subjects made errors of commission. 相似文献
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本研究旨在研究示意性符号的阈下情绪启动效应。采用三明治掩蔽技术记录了不同时间间隔 （83ms和583ms1）正、负性示意性符号都产生了阈下情绪启动效应;（2）时间间隔（SOA）会影响示意性符号的情绪启动效果,较短的SOA水平下,示意性符号的正性情绪启动效果较差;（3）启靶刺激效价一致相比于不一致时,更容易启动相对应的情绪。 相似文献
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通过提取湿地内外滇池水体水样中的微囊藻毒素,检测湿地内外水体中微囊藻毒素对小鼠的生殖毒性,以及对其体外和体内精子活性的影响.结果表明：湿地外周滇池水体中的微囊藻毒素对小鼠具有生殖毒性,特别在精子的生成和精子活性方面表现出较强的毒性作用;湿地内水体的生殖毒性明显低于湿地外水体,对小鼠的睾丸和附睾不会形成器质性变化,也不会影响精子的数量和精子活性（与对照组比较P〉0.05）.结果证实湿地能有效抑制滇池水体中微囊藻毒素的形成,对滇池水质可起到有效的净化作用. 相似文献
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林志友 《河南师范大学学报(哲学社会科学版)》2007,34(3):47-49
毛泽东与当时中共的其他领导人相比,他真正把握了马克思的按劳分配的本意。同时,毛泽东尤其相信,战争年代的那种革命热情,并不是物质激励刺激出来的,在建设年代实行供给制,照样可以出旺盛的斗志。毛泽东当时具有理论和实践这两大资源是他选择以精神激励为主的方式发展中国经济的主要原因。 相似文献
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Objective: We dynamically measured serum inhibin B and estradiol in the early stage of hormonal stimulation to predict the ovarian response in in vitro fertilization (IVF) treatment. Methods: A total of 57 patients (<40 years of age) who un-derwent the first cycle of long protocol IVF or introcytoplasmic sperm injection (ICSI) treatment were included. Serum inhibin B, estradioi, follicle stimulating hormone (FSH) and luteinizing hormone (LH) levels were measured four times: (i) on Day 3 of the menstrual cycle (basal); (2) on the day before the first administration of gonadotrophin (Gn) (Day 0); (3) on Day 1 of Gn therapy; and (4) on Day 5 of Gn therapy. Comparisons of these measurements with ovarian responses and pregnancy outcomes were made and analyzed statistically. Results: (1) On Day 1 and Day 5 of recombinant FSH (rFSH) stimulation, ovarian response, i.e., numbers of follicles, oocytes, fertilized oocytes, and embryos, had a positive correlation (rS=0.46～0.61, P=0.000) with raised inhibin B and estradiol concentrations, but a negative correlation (rS=-0.67～-0.38, P=0.000 or P<0.01) with total rFSH dose and total days ofrFSH stimulation. (2) No significant variation (P>0.05) between the pregnant and non-pregnant groups on the basis of mean age or on all hormone concentrations at four times of the IVF cycle was observed. However, all the seven patients aged >35 years did not reach pregnancy. Conclusions: (1) Serum inhibin B and estradiol concentrations obtained shortly after Gn therapy may offer an accurate and early prediction of ovarian response; (2) Low levels of serum inhibin B and estradiol obtained shortly after Gn stimulation indicate the need for a longer period of Gn treatment and a higher daily dosage; (3) No obvious pregnancy difference among patients of age <35 years was found; however, IVF pregnancy outcome is significantly lower in women of age >35 years. 相似文献
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Qiu Y Wang LG Jia YF Yang DT Zhang MH Zhang YP Zhang LH Gai L 《Journal of Zhejiang University. Science. B》2011,12(6):448-454
The aim of the present study is to analyze sperm membrane changes and the spermicidal effect in treatment with the crude extract
from Polygala tenuifolia Willd (PTW) in vitro. The root of PTW was extracted in distilled water. Normal human spermatozoa were used to assess the
spermicidal activity (Sander-Cramer assay) of the extract from the PTW root. The hypo-osmotic swelling (HOS) test and the
eosin Y (EY) staining were used to detect the integrity of sperm membrane and vitality. The sperm chromatin dispersion (SCD)
test was performed to determine sperm DNA integrity. N-9 was used as a reference standard and semen added to physiological
saline was used as the control. Semen samples were donated by 42 healthy fertile men. The crude extract from the root of PTW
could immobilize and kill 100% spermatozoa within 20 s in vitro at the concentrations of 20.0 and 10.0 mg/ml; at the concentration
of 5.0 mg/ml, spermatozoa were immobilized in (39.5±3.2) s. In the groups of the crude extract from the root of PTW and N-9
solution, the rate of the normal HOS (tails swollen) and the white head (unstained) was 0%, and the rate of the abnormal HOS
(tails unswollen) and red head (stained) was 100%. Sperm DNA fragmentation showed no change in exposure to the crude extract
from the root of PTW and N-9 solution. The sperm revival test did not show any spermatozoa that recovered their motilities.
The rapid spermicidal activity of the crude extract from the root of PTW in vitro may occur by the disruption of the sperm
membrane integrity. 相似文献