测试 - 高级

What if you wanted more brown mice?
::如果你想要更多棕鼠呢?

Is it a new dominant or recessive trait? What is the genotype of the mouse's parents? To determine the genotypes, a testcross could be done. With mice this can be done very quickly.
::鼠标父母的基因类型是什么?为了确定基因类型,可以进行测试。老鼠可以很快进行测试。

Testcross and Punnett Squares
::测试和Punnett广场

If an individual has the dominant phenotype , is the genotype always known? Not necessarily as both a homozygous dominant and heterozygous genotype can result in the same dominant phenotype. So what would be done if it was necessary to know the genotype? A testcross can be used to determine the organism's genotype. In a testcross, the individual with the unknown genotype is crossed with a homozygous recessive individual ( Figure  ).
::如果一个人有主要的苯型,基因型总是为人所知吗?不一定同时是同质主宰型和异体正态基因型都会产生同样的主要苯型。所以如果有必要知道基因型,将怎么办?一个测试可以用来确定有机体的基因型。在测试中,具有未知基因型的人会与同质休眠人(图 ) 交叉(图 ) 。

Consider the following example: Suppose you have a purple and white flower and purple color ( P ) is dominant to white ( p ). The white flower must be homozygous for the recessive allele , but the genotype of the purple flower is unknown. It could be either PP or Pp . A testcross will determine the organism's genotype. The unknown genotype can be determined by observing the phenotypes of the resulting offspring. If crossing the unknown dominant phenotype ( PP or Pp genotype) individual with the recessive phenotype individual produces only dominant phenotypes (no recessive), then the unknown individual is homozygous dominant. If any recessive phenotypic individuals result from the cross, then the unknown individual must carry the recessive allele, and have the heterozygous genotype.
::以下列示例为例: 假设您有紫色和白花,紫色色( P) 以白色为主( p) 。 白花必须是静脉型的同卵体, 但紫色花的基因类型未知。 它可以是 PP 或 Pp 。 测试将决定生物体的基因类型。 未知基因类型可以通过观察所生后代的苯型来确定。 如果穿越未知的主要pheno型( PP 或 Pp geno 型) 个人与静脉型个体之间的交错只产生占主导地位的苯型( 无静脉型 ) , 那么未知个体则具有同卵型 。 如果任何静脉型个人从十字中产生, 那么未知个体必须携带静脉型的静脉冲, 并带有异细胞基因型 。

In the example shown here, a testcross is done to determine the genotype of a parental Agouti rat. Agouti ( A ) refers to a pattern of pigmentation in which individual hairs have several bands of light and dark pigment with black tips, and is the common color of the Norway rat, Rattus norvegicus . Agouti is the dominant phenotype, and in this example, has the genotypes AA or Aa. White fur color is the recessive phenotype, with a aa genotype. If rats with white fur result from the parental cross, then both parents must carry the recessive allele, and the unknown parent must have an Aa genotype.
::在此处所举的例子中,为了确定父母的阿古蒂大鼠的基因型,做了一个测试。阿古蒂(A)是指一种色化模式,即个人毛有几条光带和黑色带黑尖的黑色带,这是挪威大鼠拉图斯·诺维吉古斯(Rattus Norvegicus)的普通颜色。阿古蒂是主要的苯型,在这个例子中,它有基因型AA或Aa。白毛色是一种隐性芬型,具有一种基因型。如果长于白毛的老鼠是父母的杂交,那么父母双方必须携带休眠异色色带,而未知的父母必须有一个甲型。

Determining Missing Genotypes
::确定缺少的基因类型

A can also be used to determine a missing genotype based on the other genotypes involved in a cross. Suppose you have a parent plant with purple flowers and a parent plant with white flowers. Because the b is recessive, you know that the white-flowered parent must have the genotype bb . The purple-flowered parent, on the other hand, could have either the BB or the Bb genotype. The Punnett square in Figure  shows this cross. The question marks (?) in the chart could be either B or b alleles.
::A 也可以用来根据十字架上涉及的其他基因型确定缺失的基因型。 假设您有带有紫花的母植物, 和带有白花的母植物。 因为 b 是休眠性的, 您知道白花父母必须有基因型bb。 另一方面, 紫花父母可以有 BB 或 Bb 基因型。 图中的 Punnett 方形显示了这个十字。 图表中的问题标记(? ) 可以是 B 或 balleles 。

Can you tell what the genotype of the purple-flowered parent is from the information in the Punnett square? No; you also need to know the genotypes of the offspring in row 2. What if you found out that two of the four offspring have white flowers? Now you know that the offspring in the second row must have the bb genotype. One of their b alleles obviously comes from the white-flowered ( bb ) parent, because that’s the only allele this parent has. The other b allele must come from the purple-flowered parent. Therefore, the parent with purple flowers must have the genotype Bb .
::您能否从 Punnett 广场的信息中知道紫花父母的基因类型? 不, 您也需要知道第二排的后代的基因类型。 如果您发现四个后代中有两个有白花呢? 现在您知道第二排的后代必须有bb 基因类型。 他们的卵巢之一显然来自白花(bb) 父母, 因为这是这个家长唯一的外号。 另一根蛋必须来自紫花父母。 因此, 带紫花的父母必须有色花Bb。

Summary
::摘要

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• A testcross examines the genotype of an organism that shows the dominant phenotype for a given trait.
  ::测试十字检查显示某一特性的主要苯型生物的基因型。
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• In a testcross, an organism with an unknown genotype but dominant phenotype is crossed with an organism that is homozygous recessive for the same trait.
  ::在测试中,一个具有未知基因型但占支配地位的苯型生物体与一个具有同一特性的同卵蛋的有机体交叉。

Review
::回顾

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1. Identify the purpose of a testcross.
   ::识别测试的目的。
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2. Give an example of in which a testcross would be utilized. Provide the parental and offspring genotypes and phenotypes.
   ::请举一个例子,说明将如何使用测试交叉。 提供亲子基因类型和苯型。
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3. Assume tall (T) is dominant to dwarf (t). If a homozygous dominant individual is crossed with a homozygous dwarf, the offspring will have what ratio?
   ::以高(T)为主的矮人(t)占优势。 如果一个同性古人占优势的个人与同性古人矮人交叉,那么后代将具有什么比例?
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4. In a cross between two heterozygotes (Aa), the next generation will have what ratio of homozygotes to heterozygotes?
   ::在两个异体酶蛋白(Aa)之间的交叉体中,下一代的同体酶与异体酶蛋的比重是多少?
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5. Huntington's disease is due to an autosomal dominant allele. If a heterozygous male marries a normal female, what percentage of the offspring will have Huntington's?
   ::Huntington的疾病是由一个自动的单体细胞占支配地位的异性通灵造成的。 如果一个异性性突变的男性嫁给了正常的女性,那么亨廷顿的后代中有多少比例会生下亨廷顿的呢?