本帖最後由 fish 於 12/3/2010 10:40 AM 編輯
仲有冇人知點解vascular bundle係stem度係locate係周圍而唔係中間??有咩重要性?
Structure implies function.
Vascular bundle 包含xylem, 除transport外還有support的作用
Stem有support 整株植物的作用, 如果把Vascular bundle集中於一點的話, support 會較弱,
如果將vascular bundle分散去周圍的話就會較強
就好像大多建築物都靠要一堆樁/柱來支撐而不是只有一條樁/柱在中間一樣
if a human baby boy inherits a recessive allele from his mother,in which circumstance would be most likely show the trait coded for by the recessive allele?
A.the baby inherits the dominant allele from his father
B.the allele is o an autosomal chromosome and the baby is a twin
C.the allele is on the X chromosome
D.the allele is on the Y chromosome
我想問點解答案係C唔係D? 佢已經係媽媽度拎左條allele,,姐係X chromosome度已經有啦,,如果要show 個trait 唔係應該要有1條recessive allele 係爸爸(X chromsome)度先得咩? 另外不解autosomal chromosome點解= =""
Autosomal chromosome = autosome = non-sex chromosome
以人為例的話就是除XY外的22對chromosome了
題目所說的是baby boy, 男性, 所以他的sex chromosome是 XY (X from mother, Y from father)
如果那個recessive trait 是在 autosome上, 那就需要一對recessive allele 才會express
如果那個recessive trait 是在 Y chromosome上, 母親是不能該把trait遺傳給兒子的(因為Y from father)
如果那個recessive trait 是在 X chromsome上, 由於男性只有一條X chromosome而且必定是由母親給予的, 所以(在這case)那個recessive trait 理論上一定會express |
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發表於 10/3/2010 11:39 PM 
發表於 12/3/2010 10:38 AM 