英语周报2022-2022外研版第四期。答案

Paragraph 1On Monday morning, hiding behind the window, wesoon saw what we were waiting for. It turned out that there They were too funny as they hopped away holding theirwere three of them from our school. They sneaked up on injured feet. We just couldn't contain our happiness andour snowman and sneered. Taking their places on either i excitement. With a hearty laugh, we came out of hidingside, they pulled back their legs to deliver powerful kicks. and sprang into the yard from inside the house. " An eye forBut the moment they hit the hard ice block of the base,. an eye! Justice done! "We yelled behind them. And thatsneers turned into shock, then agony and tears. They was the end of our problems with the snow bullies. Everhowled and cursed, gritting their teeth and stomping their i since then, our snowman was kept guarded and intact untilhappily melted into spring water and finally wove into ourParagraph 2sweetest childhood memoriesSeeing their pained looks, we couldn t help laughing

22.(14分,每空2分)(1)该植物是XY型性别决定的生物,性染色体X和Y是两条异型的同源染色体,它们所含有的基因有差异,因此需要测定12条常染色体和X、Y染色体上的DNA序列(合理即可)不需要进行去雄(2)常F1无论雌雄红花:白花均为3:1(3)AaXX AaXY(4)aD【解析】(1)该植物是XY型性别决定的生物,性染色体X和Y上有非同源区段,所含有的基因种类不同,因此,测定该植物基因组的遗传信息需要测定14条染色体上的DNA序列。在杂交时,雌雄异株的植物不需要进行去雄。(2)由表中数据可知,F1无论雌雄,红花:白花均为3:1,没有性别差异,说明控制花色的基因位于常染色体上。(3)两亲本中红花基因型均为Aa,由F1中雌株都是无芒,雄株无芒:有芒=1:1可知,无芒为显性,且控制有芒和无芒的基因位于X染色体上,根据以上分析,亲本红花无芒雌性植株的基因型为 AaX X,红花无芒雄性植株的基因型为 AaXY。(4)由杂交结果可知,亲本红花抗锈病与白花易感锈病的基因型分别为AADD、ad,F1的基因型为AaDd,F1雄性植株能产生AD、Ad、aD、ad四种可育配子,F1雌性植株产生的可育配子只有AD、AdaD、ad中的三种;F1后代的表型及比例为红花抗锈病:红花易感锈病:白花抗锈病:白花易感锈病=7:3:1:1,这一比例是9:3:3:1的变式,通过比较两个比例可知,F1产生的不育雌配子的基因型为aD

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