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  • 染色体 - 高级

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    Coiled bundles of DNA and proteins, containing hundreds or thousands of genes. What are these things?
    ::堆肥的DNA和蛋白质包裹,含有数百或数千个基因。这些是什么?

    Chromosomes. Usually people have 46 of them, 23 from each parent. These "X-shaped" structures ensure that each receives the proper amount of during . The DNA coils into these structures that makes proper separation during and possible.
    ::染色体。 通常人们有46个, 23个来自父母双方。 这些“ X形”结构确保每个人在 染色体期间得到适当的数量 。 DNA圈会进入这些结构, 从而在时间和可能性上进行适当的分离 。

    Chromosomes and Genes
    ::染色体和基因

    The consists of 24 distinct chromosomes: 22 autosomal chromosomes plus the sex-determining X and Y chromosomes. A chromosome is a threadlike molecule of genes and other DNA located in the of a cell. Different organisms have different numbers of chromosomes. Human somatic cells have 23 chromosome pairs for a total of 46 chromosomes: two copies of the 22 autosomes (one from each parent), plus an X chromosome from the mother and either an X or Y chromosome from the father ( Figure  ).
    ::由24个不同的染色体组成:22个自动单色体染色体,加上性别确定型X和Y染色体。染色体是细胞内基因和其他DNA的线状分子。不同的生物有不同数量的染色体。人类的染色体细胞有23对染色体,共46个染色体:22个染色体的两份副本(每对母体一份),加上母亲的X染色体和父亲的X或Y染色体(图示)。

    lesson content
    The human genome has 23 pairs of chromosomes located in the nucleus of somatic cells. Each chromosome is composed of genes and other DNA wound around histones (proteins) into a tightly coiled molecule.
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    Human Chromosomes. Human chromosomes are shown here arranged by size. Chromosome 1 is the largest, and chromosome 22 is the smallest. All normal human cells (except gametes) have two of each chromosome, for a total of 46 chromosomes per cell. Only one of each pair is shown here.
    lesson content
    Human Chromosomes. Humans have 23 pairs of chromosomes. Pairs 1-22 are autosomes. Females have two X chromosomes, and males have an X and a Y chromosome.

    There are an estimated 20,000-23,000 human protein-coding genes, but many more . Most human genes have multiple eons (coding sequences) separated by much larger introns (non-coding sequences). Regulatory sequences controlling are associated with exon sequences. The introns are usually excised (removed) during post-transcriptional modification of the mRNA. Human cells make significant use of alternative splicing (see the concepts) to produce a number of different proteins from a single gene. So even though the human genome is surprisingly similar in size to the genomes of simpler organisms, the human proteome is thought to be much larger. A proteome is the complete set of proteins expressed by a genome , cell, tissue , or organism.
    ::人类蛋白质编码基因估计有20,000-23,000个人类蛋白质编码基因,但更多的基因。大多数人类基因有多个电子(编码序列),由大得多的电子(非编码序列)分离出来。监管序列控制与外序相关。调节序列通常在对 mRNA进行移植后修改时切割(移走)。人类细胞大量使用替代配方(见这些概念)从单一基因中产生若干不同的蛋白质。因此尽管人类基因组在规模上与较简单的生物基因组非常相似,但人们认为人的蛋白质要大得多。一个蛋白质是由基因组、细胞、组织或生物体表示的一整套蛋白质。

    Linkage
    ::链接

    As stated above, our roughly 20,000+ genes are located on 24 distinct chromosomes. So many genes are located on the same chromosome. Chromosome 1 is the largest chromosome with approximately 246 million base pairs, whereas chromosome 21 and 22 are the smallest chromosomes, with just under 50 million base pairs each. 
    ::如上所述,我们大约20,000+基因位于24个不同的染色体上,许多基因位于同一个染色体上。 染色体1是最大的染色体,大约有2.46亿对基对,而染色体21和22是最小的染色体,每对基对略低于5000万对。

    Linkage refers to particular genetic loci , or inherited together, suggesting that they are physically on the same chromosome, and located close together on that chromosome. Two or more loci that are on the same chromosome are physically connected and tend to segregate together during meiosis, unless a cross over event occurs between them. A crossing-over event during prophase I of meiosis is rare between loci that usually segregate together; these loci will usually be close together on the same chromosome. They are, therefore, said to be linked. Alleles for genes on different chromosomes are not linked; they sort independently (independent assortment) of each other during meiosis.
    ::链接是指特定遗传原体,或一起继承,表明它们物理上处于同一染色体上,并紧紧地放在该染色体上。同一染色体上的两个或两个以上原体在身体上相连,除非它们之间发生交叉事件,否则在美化期间往往会相互分离。在前期一期的梅氏病期间,经常相互隔离的原体之间很少发生交叉事件;这些原体通常在同一个染色体上紧密相连。因此,它们据说是相连的。不同染色体上的基因的异体没有相互联系;在美化期间,它们彼此独立地(独立地)分类。

    A gene is also said to be linked to a chromosome if it is physically located on that chromosome. For example, a gene (or loci) is said to be linked to the X-chromosome if it is physically located on the X-chromosome chromosome. The physical location of a gene is important when analyzing the inheritance patterns of phenotypes due to that gene. The inheritance patterns of phenotypes may be different if the gene is located on a sex chromosome or an autosome. This will be further discussed in additional Human Genetics concepts.
    ::据说,如果基因实际位于染色体上,也与染色体有关联,例如,如果基因(或 Loci)实际位于X-染色体上,据说与X-染色体有关联。在分析该基因导致的苯型继承模式时,基因的实际位置很重要。如果该基因位于性染色体上或自体,那么苯型的继承模式可能不同。其他人类基因概念将进一步讨论这个问题。

    Linkage Maps
    ::链接地图

    The frequency of recombination refers to the rate of crossing-over ( recombination ) events between two loci. This frequency can be used to estimate genetic distances between the two loci, and create a linkage map . In other words, the frequency can be used to estimate how close or how far apart the two loci are on the chromosome.
    ::重新组合的频率是指两个地方之间的交叉重叠(再组合)事件的频率。该频率可用于估计两个地方之间的遗传距离,并绘制链接地图。换句话说,该频率可用于估计这两个地方在染色体上的距离或距离。

    In the early 20 th century, Thomas Hunt Morgan, working with the fruit fly Drosophila Melanogaster , showed that genes can be linked. He showed that genes located on the same chromosome do not show independent assortment . He was able to demonstrated that the amount of crossing over between linked genes differs. This led to the idea that the frequency of crossover events would indicate the distance separating genes on a chromosome. Morgan's student, Alfred Sturtevant, developed the first genetic map, also called a linkage map.
    ::20世纪初,托马斯·亨特·摩根(Thomas Hunt Morgan)与果蝇Drosophila Melanogaster(Drosophila Melanogaster)合作,表明基因是可以联系在一起的。他显示,同一染色体上的基因没有显示独立的分类。他能够证明,连接的基因之间的交叉量不同。这导致一种想法,即交叉事件的频率将显示染色体上的基因分离的距离。摩根的学生Alfred Sturtevant(Alfred Sturtevant)开发了第一张基因图,也称为连接图。

    Sturtevant proposed that the greater the distance between linked genes, the greater the chance that non-sister chromatids would cross over in the region between the genes during meiosis. By determining the number of recombinants - offspring in which a cross-over event has occured - it is possible to determine the approximate distance between the genes. This distance is called a genetic map unit (m.u.), or a centimorgan , and is defined as the distance between genes for which one product of meiosis in 100 products is a recombinant. So, a recombinant frequency of 1% (1 out of 100) is equivalent to 1 m.u. Loci with a recombinant frequency of 10% would be separated by 10 m.u. The recombination frequency will be 50% when two genes are widely separated on the same chromosome or are located on different chromosomes. This is the natural result of independent assortment. Linked genes have recombination frequencies less than 50%. Thomas Hunt Morgan also demonstrated linkage to sex chromosomes in Drosophila.  
    ::Sturtevant 提议,连接基因之间的距离越大,非姐妹染色体在地中海期间在区域基因之间跨过非姐妹染色体的可能性就越大。通过确定再组合剂的数量 -- -- 发生交叉事件的后代 -- -- 有可能确定基因之间的大致距离。这一距离被称为基因图单元(m.u.),或半有机体,被定义为100种产品中一种梅氏病产物是再结合剂的基因之间的距离。因此,100种产品中的1%(100种中的1种)的再组合频率相当于1 m.u.u.。再组合频率为10%的洛西将用10 m.u.u.分开。当两个基因在同一染色体上广泛分离或位于不同的染色体上时,再组合频率将为50%。这是独立的分解的自然结果。连接基因的再组合频率小于50%。托马斯·亨特摩根还表明,在Drophis中,与性别染色体中的染色体有联系。

    Determining recombination frequencies between genes located on the same chromosome allows a linkage map to be developed. Linkage mapping is critical for identifying the location of genes that cause genetic diseases.
    ::确定位于同一染色体上的基因之间的重组频率,可以绘制链接图。 链接绘图对于确定造成遗传疾病的基因的位置至关重要。

    lesson content
    Linkage Map for the Human X Chromosome. This linkage map shows the locations of several genes on the X chromosome. Some of the genes code for normal proteins. Others code for abnormal proteins that lead to genetic disorders. Which pair of genes would you expect to have a lower frequency of crossing-over: the genes that code for hemophilia A and G6PD deficiency, or the genes that code for protan and Xm?

    Summary
    ::摘要

    • The human genome consists of 24 distinct chromosomes: 22 autosomal chromosomes, plus the sex-determining X and Y chromosomes.
      ::人类基因组由24个不同的染色体组成:22个自相相色谱体,加上性别确定X和Y染色体。
    • Linkage refers to particular genetic loci or alleles inherited together, suggesting that they are physically on the same chromosome, and located close together on that chromosome.
      ::联系是指共同继承的特定遗传地貌或异系物,表明它们实际上在同一染色体上,紧紧地放在该染色体上。

    Review
    ::回顾

    1. What does the term linkage refer to?
      ::联系一词指的是什么?
    2. What is a linkage map? What helps create a linkage map?
      ::什么是连接图?什么有助于创建连接图?
    3. What did Thomas Hunt Morgan discover?
      ::Thomas Hunt Morgan发现了什么?
    4. What did Alfred Sturtevant propose?
      ::Alfred Sturtevant有什么建议?
    5. G and I have a recombination frequency of 8.5%. G and H have a recombination frequency of 14%. H and I have a recombination frequency of 22.5%. Use these values to construct a rudimentary map for the chromosome that will tell you the order of the three genes relative to each other along the chromosome. Will this information also tell you the genes absolute position on the chromosome?
      ::G和我的重组频率为8.5%。G和H的重组频率为14%。H和我的重组频率为22.5%。用这些数值来构建一个基本的染色体分布图,该图将告诉你染色体沿染色体相相对的三个基因的顺序。这个信息还会告诉你染色体上的基因绝对位置吗?