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anita369 asked in 科學化學 · 8 years ago

生物-科學班考題

請各位大大幫忙解析一下,謝謝! (選擇題)

下表為五種核酸分子的含氮鹼基百分比。試問哪個核酸分子為雙股DNA且

解鏈溫度(melting temperature)最低?

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核酸分子...%腺嘌吟...%鳥糞嘌吟...%胸腺嘧啶...% 胞嘧啶...%脲嘧啶

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甲..................33...............17.. ...............33 ..............17 ............. 0

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乙..................33...............33 .................17................17..............0

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丙..................26...............24...................0.................24.............26

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丁..................28...............22..................28................22...............0

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戊..................21...............40................. 21................18...............0

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(A) 甲 (B) 乙 (C) 丙 (D) 丁 (E) 戊

2 Answers

Rating
  • ?
    Lv 7
    8 years ago
    Favorite Answer

    您好!

    我的解答:

    正確答案是A---

    1.雙股DNA的話,比例上A=T,C=G,且沒有U,所以只剩下甲和丁

    2.DNA的解鏈溫度(Tm)是引物的一個重要參數,它是當50%的引物和互補序列表現為雙鏈DNA分子時的溫度,一種DNA分子的Tm值大小與其所含鹼基中的G+C比例相關,G+C比例越高,Tm值越高。所以解鏈溫度要低,表示G+C比例低,故選(A)甲

    註:腺嘌呤代號為A,鳥糞嘌呤代號為G,胸腺嘧啶代號為T,胞嘧啶代號為C,脲嘧啶代號為U

    Source(s): 百度
  • ?
    Lv 5
    8 years ago

    A只與T相連,而C只與G相連

    尿嘧啶是rna的

    胸腺嘧啶T與腺嘌呤A比例要相同

    鳥嘌呤G與胞嘧啶C比例要相同

    GC越多解鏈溫度越高

    因此答案選(A) 甲

    Source(s): ME
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