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词汇 Unequal crossover
分类 英语词汇 英语翻译词典
释义

Unequal crossover

中文百科

染色体互换 Chromosomal crossover

（重定向自Unequal crossover）
托马斯·亨特·摩根于1916年所绘制的互换图。
双重互换。

染色体互换（英语：Chromosomal crossover）也称互换，又译染色体交换。是指两条染色体在减数分裂第一前期进行配对时，部分的DNA发生交换。互换通常是某一染色体的一部分断裂，并接到另一条染色体上。此过程所造成的结果，称为遗传重组。

最早描述并提出互换理论的科学家是托马斯·亨特·摩根，而最早确认互换物理基础的人，则是巴巴拉·麦克林托克等人。

英语百科

Chromosomal crossover 染色体互换

（重定向自Unequal crossover）
Crossing over occurs between prophase 1 and metaphase 1 and is the process where homologous chromosomes pair up with each other and exchange different segments of their genetic material to form recombinant chromosomes. It can also happen during mitotic division,[1] which may result in loss of heterozygosity. Crossing over is essential for the normal segregation of chromosomes during meiosis. Crossing over also accounts for genetic variation, because due to the swapping of genetic material during crossing over, the chromatids held together by the centromere are no longer identical. So, when the chromosomes go on to meiosis II and separate, some of the daughter cells receive daughter chromosomes with recombined alleles. Due to this genetic recombination, the offspring have a different set of alleles and genes than their parents do. In the diagram, genes B and b are crossed over with each other, making the resulting recombinants after meiosis Ab, AB, ab, and aB.
Thomas Hunt Morgan's illustration of crossing over (1916)
A double crossing over
A current model of meiotic recombination, initiated by a double-strand break or gap, followed by pairing with an homologous chromosome and strand invasion to initiate the recombinational repair process. Repair of the gap can lead to crossover (CO) or non-crossover (NCO) of the flanking regions. CO recombination is thought to occur by the Double Holliday Junction (DHJ) model, illustrated on the right, above. NCO recombinants are thought to occur primarily by the Synthesis Dependent Strand Annealing (SDSA) model, illustrated on the left, above. Most recombination events appear to be the SDSA type.

Chromosomal crossover (or crossing over) is the exchange of genetic material between homologous chromosomes that results in recombinant chromosomes during sexual reproduction. It is one of the final phases of genetic recombination, which occurs in the pachytene stage of prophase I of meiosis during a process called synapsis. Synapsis begins before the synaptonemal complex develops and is not completed until near the end of prophase I. Crossover usually occurs when matching regions on matching chromosomes break and then reconnect to the other chromosome.
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