OG48-5(實在是太難懂，讓我們一起突破困境)

[黃婉君]

*25. It can be inferred from the passage that the morphogenetic determinants present in the early embryo are (推論題)
(A) located in the nucleus of the embryo cells 明顯與原文不符，事實上，MD是在細胞質中
(B) evenly distributed unless the embryo is not developing normally 不均勻才對
(C) inactive until the embryo cells become irreversibly committed to their final function 活躍才對
(D) identical to those that were already present in the unfertilized egg 文中未提及
(E) present in larger quantities than is necessary for the development of a single individual
我做錯了，答案E，但想不通是如何推論的


這一題我也不懂 為何是E?
我選C
請各位高手幫忙解一下

[dibert8]

OG 的解釋似乎還蠻合理:
The second and third paragraphs of the passage indicate that morphogenetic determinants are substances in the embryo that are activated after the egg has been fertilized and that “tell a cell what to become” (lines 21-23). If, as the author asserts in the first paragraph, biologists have succeeded in dividing an embryo into two parts, each of which survives and develops into a normal embryo, it can be concluded that the quantity of morphogenetic determinants in the early embryo is greater than that required for the development of a single individual.

因為胚胎切兩半,各自可以長出完整的胚胎,至少就有兩份完整的 MD, 所以比長成一個個體所需要的(一份)來要多囉!

[黃婉君]

謝謝 dibert8 大的回答
看完一遍又一遍的OG 解釋
加上 dibert8大的中文解釋
我體會到為何要選E
關鍵在於知道MD 是什麼

[chris8888]

這題真難, 要彙整三段(1, 2, 3),
第一段說早期被切可以長成獨立個體,
第二段說他可以決定細胞要長成怎樣? 所以被切後他會告訴細胞要怎樣去長大
第三段說受精後他很活躍,

所以可以看出既然可以在早期把它切開, 然後可以發展成兩個實體, 那就表示早期的MD數量上會多過於發展單一個體所需要的的MD,

所以當生物學家把它切成兩份, 它可以長出兩個, 若不切他就是發展出一個個體, 證明他在早期時胚胎具備足以發展出超過一個個體的MD數量, 只是看生物學家要不要去切它, <== can be inferred from the first paragraph.

若不切, 它就只是一個個體, 切了就變成兩個個體, 各自都有自己的MD會去主導這個形體的器官繁衍