Section outline

  • General

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  • 概率

    What you will learn
    ::你会学到什么

    • What is probability
      ::什么是概率
    • How rules of probability are applied to determine the phenotypes and genotypes of offspring
      ::如何运用概率规则确定后代的苯型和基因型

    A roulette wheel showing different numbered slots and a single white ball.

    What are the odds of landing on 23 again?
    ::23号着陆的几率有多大?

    Not as high as inheriting an from a parent. Probability plays a big role in determining the chance of inheriting an allele from a parent. It is similar to tossing a coin. What's the chance of the coin landing on heads?
    ::概率在决定从父(母)继承异性(异性)的可能性方面起着很大的作用。它类似于抛硬币。硬币在头顶着陆的可能性是多少?

    Probability
    ::概率

    Assume you are a plant breeder trying to develop a new variety of plant that is more useful to humans. You plan to cross-pollinate an insect-resistant plant with a plant that grows rapidly. Your goal is to produce a variety of plant that is both insect resistant and fast growing. What percentage of the offspring would you expect to have both characteristics? Mendel’s laws can be used to find out. However, to understand how Mendel’s laws can be used in this way, you first need to know about probability.
    ::假设你是一个植物育种者,试图开发一种对人类更有用的新品种植物。你计划用一种迅速生长的植物交叉污染一个抗虫植物。你的目标是生产多种抗虫植物和快速生长的植物。你期望后代中具有两种特性的比例是多少?可以利用门德尔的法律来发现。然而,为了了解曼德尔的法律是如何用这种方法的,你首先需要了解概率。

    Probability is the likelihood, or chance, that a certain event will occur. The easiest way to understand probability is with coin tosses (see the  Figure ). When you toss a coin, the chance of a head turning up is 50 percent. This is because a coin has only two sides, so there is an equal chance of a head or tail turning up on any given toss.
    ::概率是某个事件发生的可能性或概率。 最容易理解概率的方法是抛硬币( 见图 ) 。 抛硬币时, 头的出现概率为 50% 。 这是因为硬币只有两面, 所以在任何给定的抛硬币上,头或尾都有相同的机会出现头或尾。

    A person tossing a coin, depicting the randomness of outcomes in probability.
    Tossing a Coin. Competitions often begin with the toss of a coin. Why is this a fair way to decide who goes first? If you choose heads, what is the chance that the toss will go your way?

    If you toss a coin twice, you might expect to get one head and one tail. But each time you toss the coin, the chance of a head is still 50 percent. Therefore, it’s quite likely that you will get two or even several heads (or tails) in a row. What if you tossed a coin ten times? You would probably get more or less than the expected five heads. For example, you might get seven heads (70 percent) and three tails (30 percent). The more times you toss the coin, however, the closer you will get to 50 percent heads. For example, if you tossed a coin 1000 times, you might get 510 heads and 490 tails.
    ::如果抛硬币两次,你可能会期望得到一头和一尾。但每次抛硬币一次,头的机会仍然是50%。因此,你很有可能会连续得到两个甚至几个头(或尾巴)。如果你抛了10次硬币呢?你可能会得到多于或少于预期的5个头。例如,你可能会得到7个头(70%)和3个尾巴(30% ) 。但是,每次抛硬币一次,头的机会还是50%。例如,如果你扔了1 000次硬币,你可能会得到510个头和490个尾巴。

    Probability and Inheritance
    ::概率和继承权

    The same rules of probability in coin tossing apply to the main events that determine the genotypes of offspring. These events are the formation of gametes during and the union of gametes during .
    ::抛硬币的概率规则同样适用于决定后代基因类型的主要事件。 这些事件是在 . . . . . . . . . . . . . . . . . . . . . . . . .

    Probability and Gamete Formation
    ::概率和久调形成

    How is gamete formation like tossing a coin? Consider Mendel’s purple-flowered again. Assume that a plant is heterozygous for the flower-color allele, so it has the genotype Pp  (see the  Figure ). During meiosis, homologous chromosomes , and the alleles they carry, segregate and go to different gametes. Therefore, when the Pp pea plant forms gametes, the P and p  alleles segregate and go to different gametes. As a result, half the gametes produced by the Pp parent will have the P allele and half will have the p allele. Based on the rules of probability, any given gamete of this parent has a 50 percent chance of having the P allele and a 50 percent chance of having the p allele.
    ::游戏组是如何形成像抛硬币一样的? 考虑门德尔的紫花。 假设一个植物是花色外壳的异形,因此它有基因型Pp(见图 ) 。 在中度、同质染色体和它们携带的异形中,它们携带的、隔离和去不同的游戏区。 因此,当Pp豆植物形成游戏区,P和peles分离并进入不同的游戏区时,P和peles会分离并进入不同的游戏区。 结果,Pp父母产生的一半的游戏区将拥有Palle,而另一半将拥有。 根据概率规则,任何给定的游戏区都有50%的机会拥有Palle,还有50%的机会拥有Alele。

    Gamete formation from a heterozygous plant and a coin toss analogy.
    Formation of gametes by meiosis. Paired alleles always separate and go to different gametes during meiosis.

    Probability and Fertilization
    ::概率和肥化

    Which of these gametes joins in fertilization with the gamete of another parent plant? This is a matter of chance, like tossing a coin. Thus, we can assume that either type of gamete—one with the P allele or one with the p allele—has an equal chance of uniting with any of the gametes produced by the other parent. Now assume that the other parent is also Pp . If gametes of two Pp parents unite, what is the chance of the offspring having one of each allele like the parents ( Pp )? What is the chance of them having a different combination of alleles than the parents (either PP or pp )? To answer these questions, geneticists use a simple tool called a , which is the focus of the next concept.
    ::这些游戏中的哪一个与另一个父系植物的游戏结合?这是一个偶然的问题,就像扔硬币一样。因此,我们可以假设,两种游戏——一个与Palle或一个与ele的游戏——都具有与另一个父系所产生任何组合的同等机会。现在,假设另一个父系也是Pp。如果两个Pp父母的游戏组合在一起,那么后代拥有像父母(Pp)一样的每一个异种的可能性是多少?他们拥有不同于父母(PP或pp)的异种组合的可能性是多少?为了回答这些问题,遗传学家们使用一个简单的工具,叫做“Pp”,这是下一个概念的焦点。

    DID YOU KNOW?
    The use of probability in genetics helps to understand the likelihood of inheriting traits. An English geneticist, Reginald Punnett, devised a simple graphical way to calculate the mathematical probability of inheriting a trait. 
     

     

    Summary
    ::摘要

    • Probability is the chance that a certain event will occur. For example, the probability of a head turning up on any given coin toss is 50 percent.
      ::概率是某个事件发生的可能性。 例如, 某个头朝某个硬币投币的概率是 50% 。
    • Probability can be used to predict the chance of gametes and offspring having certain alleles.
      ::概率可以用来预测数子和后代有某些异长的可能性。

    Review
    ::回顾

    1. Define probability. Apply the term to a coin toss.
      ::定义概率。将术语应用到抛掷硬币 。
    2. How is gamete formation like tossing a coin?
      ::游戏的形成如何 喜欢抛硬币?
    3. With a PP homozygote, what is the chance of a gamete having the P allele? The p allele?
      ::和PP同性恋者在一起, 玩游戏的人有Palle的几率是多少?