【問題】有關染色體

[Mr腰果 10]

某生物的體細胞含有42條染色體，在第一減數分裂前期，細胞內含有的姊妹染色分體、染色體和DNA數量依次為 84 42 84 這樣對嗎?

請問一個染色體是由兩個姊妹染色分體組成的嗎?

[benh666 10]

是

染色體在S期就已複製完成

所以一個染色體在M期時都成對出現

[阿曼達 10]

真的是非常不好意思,

打擾了,請問一下benh666大大,

M期跟S期是...........

[s860134 11]

細胞週期分為

G1=>S=>G2=>M=>G1....

G1、G2時大多都在準備複製DNA和分裂時所需要的蛋白質

S DNA複製

M為 細胞分裂期

G1、S、G2 合稱間期

[阿柿 10]

請問一個染色體是由兩個姊妹染色分體組成的嗎?

我總覺得這行字有點不對勁...

兩個姐妹染色分體組成的叫做四分體吧..?

[benh666 10]

我總覺得這行字有點不對勁...

兩個姐妹染色分體組成的叫做四分體吧..?

A chromatid is one among the two identical copies of DNA making up a replicated chromosome, which are joined at their centromeres, for the process of cell division (mitosis or meiosis). The term is used so long as the centromeres remain in contact. When they separate (during anaphase of mitosis and anaphase 2 of meiosis), the strands are called daughter-chromosomes.

可能要先澄清一下名詞

經過S其後染色質變為兩倍

M期時捲為棒狀 並且一條染色體有兩個"染色分體(chromatide)"

似乎也可以叫做姊妹染色分體(sister cromatin)

M期又可細分成"前""前中""中""後"末"

在後期剛開始時 染色分體分離被拉至兩旁

這時兩條分開的染色分體叫做姊妹染色體

而您所說的"四分體" 則是跟減數分裂有關

During prophase I, DNA is exchanged between homologous chromosomes in a process called homologous recombination. This often results in chromosomal crossover. The new combinations of DNA created during crossover are a significant source of genetic variation, and may result in beneficial new combinations of alleles. The paired and replicated chromosomes are called bivalents or tetrads, which have two chromosomes and four chromatids, with one chromosome coming from each parent. At this stage, non-sister chromatids may cross-over at points called chiasmata (plural; singular chiasma).

減數分裂前期時

同源染色體複製 形成四個染色分體 這時四個染色分體稱為"四分體"

我已經忘記當初高中生物是不是有定義的那麼細啦