3.12 非Mendelian遗产继承 -- -- 高级
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Green, blue, brown, black, hazel, violet, or grey. What color are your eyes?
::绿色、蓝色、棕色、黑色、哈泽尔、紫色或灰色。Of course human do not come in multi-color, but they do come in many colors. How do eyes come in so many colors? Are there more than two ? Is there more than one gene ? That brings us to complex inheritance patterns, known as non-Mendelian inheritance. Many times inheritance is more complicated than the simple patterns observed by .
::当然,人类不会以多色形式出现,但确实以多种颜色出现。眼睛如何以这么多颜色出现?有超过两个的基因吗?有不止一个基因吗?这给我们带来了复杂的继承模式,被称为非曼德里亚人的继承。许多情况下,继承比观察的简单模式复杂得多。Non-Mendelian Modes of Inheritance
::非男性继承模式The relationship between genotype and phenotype is rarely as simple as the examples Mendel studied. Each characteristic he studied had two alleles, one of which was completely dominant and the other completely recessive , resulting in only two phenotypes. Geneticists now know that alleles can be codominant, or incompletely dominant, and that there are usually more than two alleles for a gene in a . Complicating issues further, some phenotypes are controlled by more than one gene.
::基因类型和苯型之间的关系很少像所研究的例子Mendel那样简单。他所研究的每个特征都有两种异灵,其中一种完全占主导地位,另一种完全处于休眠状态,仅产生两种异灵类型。 遗传学家现在知道异灵可以是共生的,也可以是不完全占主导地位,而且一个基因中通常有两种以上的异灵。 此外,一些异灵类型由不止一种基因控制。Codominance
::共居情况What happens when there are two alleles in a heterozygote and neither allele is completely dominant nor completely recessive? Can both traits appear in the phenotype? Essentially, yes they can. Can there be two dominant alleles for the same gene? Codominance occurs when both traits appear in a heterozygous offspring. For example, roan shorthorn cattle have codominant genes for hair color. The coat has both red and white hairs; not pink hairs, but red AND white hairs. The letter R indicates red hair color, and R’ white hair color. In cases of codominance, the genotype of the organism can be determined from its phenotype. The heifer in Figure shows both coat colors and therefore is RR’ heterozygous for coat color. The flower in the Figure also has two codominant alleles; it has red and white petals , not pink petals. Both colors appear in the phenotype.
::当异体阳性动物中存在两个异形时会发生什么情况? 异体阳性动物中存在两个异性动物,两个异性动物都不是完全主导性或完全消亡性? 这两种特征能否在苯型动物中出现? 基本上,它们是可以的。 同一基因中是否存在两个主要异性动物? 共性动物在异体阳性动物后代中出现两个异性动物时会出现。 比如, 红黄牛有染发的共性基因。 外衣有红色和白色头发; 不是粉色头发,而是红白头发。 字母R表示红发色, 以及R白发。 在共性动物类型中, 有机体的基因类型可以由其同性动物类型来决定。 图中的雌性动物显示了大衣的颜色, 因此是彩色的RRR ' 异性动物。 图中的花也有两种异性动物; 它有红色和白花, 不是粉色的花瓣。两种颜色都出现在同型动物中。(left) The roan coat of this cow is made up of red and white hairs. Both the red and white hair alleles are codominant. Therefore cattle with a roan coat are heterozygous for coat color (RR’). (right) The flower has red and white petals because of codominance of red-petal and white-petal alleles. Incomplete Dominance
::不完全占多数But what if there were pink petals as opposed to red and white petals? Which allele would be dominant? Both? Neither?
::但是,如果有粉红色花瓣,而不是红白色花瓣呢?哪一种花瓣会占支配地位?两者都是吗?两者都不是?Incomplete dominance occurs when the phenotype of the offspring is somewhere in between the phenotypes of both parents; a completely dominant allele does not occur. For example, when red snapdragons ( C R C R ) are crossed with white snapdragons ( C W C W ), the F 1 hybrids are all pink hetrozygotes for flower color ( C R C W ). The pink color is an intermediate between the two parent colors ( Figure ). When two F 1 ( C R C W ) hybrids are crossed they will produce red, pink, and white flowers. The genotype of an organism with incomplete dominance can be determined from its phenotype ( Table ).
::当后代的苯型在父母双亲的苯型之间某处时,就会出现完全的支配地位;完全占主导地位的异差不会发生。例如,当红松鼠(CRCR)与白松鼠(CW)交叉时,F1混合体都是花色粉色螺旋形(CRCW),粉色颜色是双向颜色(图)之间的中间体。当两个F1(CRCW)混合体经过时,它们会产生红花、粉色花和白花花。一个不完全支配的有机体的基因类型可以从其血型(表)中确定。-
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Snapdragons show incomplete dominance in the traits for flower color. The pink snapdragon has pink petals because of incomplete dominance of a red-petal allele and a recessive white-petal allele. Red Flower × White Flower allele (phenotype) C W (white) C W (white) C R (red) C R C W (pink) C R C W (pink) C R (red) C R C W (pink) C R C W (pink) Complex Forms of Heredity
::复杂的异居形式Traits that are affected by more than one gene are called . The genes that affect a polygenic trait may be closely linked on a , unlinked on a chromosome, or on different chromosomes. Polygenic traits are often difficult for geneticists to track because the polygenic trait may have many alleles. Also, independent assortment ensures the genes combine differently in gametes . Therefore, many different intermediate phenotypes exist in offspring. Eye color ( Figure ), and skin color are examples of polygenic traits in humans.
::受不止一种基因影响的基因轨迹被称为 。 影响多基因特征的基因可能紧密地连接在染色体上或不同的染色体上。 多基因特征往往难以被遗传学家追踪,因为多基因特征可能有许多灵长类。此外,独立的分类确保基因在调子中的不同组合。因此,后代中存在许多不同的中间型苯型。眼色(图示 ) , 皮肤颜色是人类多基因特征的例子。-
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Eye color and skin color are examples of polygenic traits; they are influenced by more than one gene. When three or more alleles determine a trait, the trait is said to have multiple alleles . The human ABO group is controlled by a single gene with three alleles: the dominant I A and I B , and the recessive i allele. The gene encodes an that affects that are found on the surface of the red blood cell . A and B refer to two carbohydrates found on the surface of red blood . There is not an O carbohydrate. Type O red blood cells do not have either type A or B carbohydrates on their surface.
::当三个或三个以上的异长确定一个特性时,该特性据说具有多个异长。人类ABO组由一个单一基因控制,有三个异长:占主导地位的IA和IB, 和隐性ialle。该基因编码影响到红血细胞表面。A和B是指红血表面发现的两个碳水化合物。没有O碳水化合物。O型红血细胞表面没有A型或B型碳水化合物。As the alleles I A and I B are dominant over i , a person who is homozygous recessive ( ii ) will not have type A or type B blood, but will have type O blood. Homozygous dominant I A I A or heterozygous I A i have type A blood, and homozygous dominant I B I B or heterozygous I B i have type B blood. I A I B individuals have type AB blood, because the A and B alleles are codominant. Type A and type B parents can have a type AB child. Type A and a type B parent can also have a child with Type O blood, if they are both heterozygous ( I B i , I A i ). Table shows how the different combinations of the blood group alleles can produce the four blood groups, A, AB, B, and O.
::由于IA和IB的占优势,同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系同系Bloodtype as Determined by Multiple Alleles I A I B i I A I A I A Type A I A I B Type AB I A i Type A I B I A I B Type AB I B I B Type B I B i Type B i iI A Type A iI B Type B ii Type O Summary
::摘要-
The Mendelian pattern of inheritance and expression does not apply to all traits.
::孟德尔式的继承和表达方式并不适用于所有特征。 -
Codominant traits, incompletely dominant traits, and polygenic traits do not follow simple Mendelian patterns of inheritance. Their inheritance patterns are more complex.
::共同特征、不完全的主导性特征和多源性特征并不遵循简单的门德利式继承模式。 他们的继承模式更为复杂。
Review
::回顾-
Mendelian inheritance does not apply to the inheritance of alleles that result in incomplete dominance and codominance. Explain why this is so.
::门德利人遗产不适用于导致不完全占支配地位和共占支配地位的异种人的遗产,请解释为何如此。 -
Define codominance, incomplete dominance and polygenic trait.
::界定共占、不完全的支配地位和多源特性。 -
A classmate tells you that a person can have type AO blood. Do you agree? Explain.
::同学说一个人可以有AO型血,你同意吗? -
If you cross a red plant with a white plant and the offspring is pink, what is that called?
::如果你跨过红植物和白植物 后代是粉色的 那叫什么来着?
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