Name: punnett squares for predicting traits
Uploaded: 2019-03-11T09:21:16.000Z
Duration: 1 min
Channel: JoVE

K12 Standards

Virginia  Standards of Learning

HIgh School

Life Science

LS.10

LS.10.c

Punnett Squares

【旁白】旁氏表， 一张以其发明者命名的简易图表， 以图像形式预测了 后代遗传单基因特征的概率。
 比如基于父母的基因模型，判断子女是否患有乳糖不耐。
 利用这一图表，父母一方的基因， 在这一例子中，是同型隐形的等位基因 为两个小写的l, 置于上方， 另一方，异型对偶的基因， 代表字母是一个大写的L， 和一个小写的l，写在左边， 将横竖列相交叉，在表格中得到了 子女可能形成的两种基因型 和两种表现型。
 50%是异型对偶， 能够消化乳糖。
 50%为同型隐形， 患有乳糖不耐。

爱德华兹，AWF，"雷金纳德·克伦德尔·普内特:第一位亚瑟·贝尔福遗传学教授，剑桥，1912 年。遗传学 192，第 1 期（2012 年 9 月 1 日）:3。[<a href="https://doi.org/10.1534/genetics.112.143552" target="__blank">来源</a>]

里德、詹姆斯 B. 和约翰 J. 罗斯。"孟德尔基因:迈向完整的分子表征。"遗传学 189，第 1 期（2011 年 9 月 1 日）:3。[<a href="https://doi.org/10.1534/genetics.111.132118" target="__blank">来源</a>]

punnett 方块

一个旁氏表（Punnett Squares）显示了后代可能从两个亲本遗传的基因型。如果一个性状的遗传模式（如显性或隐性）是已知的，那么旁氏表也可以用来确定遗传表型的概率。旁氏表适用于由单个基因位点决定性状遗传和性状独立遗传的情况。然而，它们无法预测更复杂的遗传情况下的性状概率。”

<h4>旁氏表（Punnett Squares）显示遗传一个或多个性状的可能性</h4>
 
旁氏表是显示两个亲本基因型交叉产生的可能后代基因型的视觉图标。它们可以描述一个或多个表型或性状的遗传，尽管其它工具更适合于研究两个以上性状的遗传。
 
旁氏表可用于确定后代遗传特定基因型或导致特定特征（即表型或特征）的一对等位基因的可能性，前提是表型是由单个基因位点引起的，并且在减数分裂期间独立分类。换言之，在遗传一个性状的可能性不影响遗传另一个性状的可能性的情况下，旁氏表对确定遗传概率很有用。尽管这些假设有许多例外（例如，由同一染色体上相邻基因编码的性状），但这些限定符对许多植物和动物性状都适用。
 
<h4>孟德尔（Mendel）的实验启发了旁氏表的诞生。</h4>
 
旁氏表是由雷金纳德·庞内特（Reginald Punnett）在20世纪初创建的，在格雷戈尔·孟德尔（Gregor Mendel）开创性的豌豆植物实验揭示了遗传的基本规律之后的几十年。如今，旁氏表经常被用来说明孟德尔实验的基本原理。
 
孟德尔研究了几种豌豆植株性状的遗传，包括豌豆和豆荚的形状和颜色、花的颜色和位置以及植株的大小。孟德尔还检查了每个特征的遗传特征。例如，紫色和白色是花颜色特征的可能特征。在豌豆植株中，紫色和白色的花是由不同的基因变异或等位基因决定的。
 
<h4>旁氏表是组织遗传信息的网格。</h4>
 
旁氏表中的每个框表示可能的受精事件，或后代基因型，由两个亲本配子产生。旁氏表通常以2x2或4x4配置排列，以分别显示一个或两个特征的遗传。
 
在命名上，等位基因由显性等位基因引起的性状的第一个字母表示。例如，由于黄色是豌豆的显性颜色特征，编码豌豆颜色的等位基因用斜体字母“y”表示。大写字母和小写字母分别表示显性和隐性等位基因。因此， Y 代表显性黄色等位基因，y 代表隐性绿色等位基因。
 
为了创建一个2x2的旁氏表来检测一个性状，图上方列出了一个亲本基因型，每列上有一个等位基因。另一个亲本基因型垂直显示在图的左边，每行旁边有一个等位基因。每个旁氏表包含与框的行和列相对应的两个亲本等位基因（每个亲本一个），表示一个可能的受精结果。完整的旁氏表内容可用于确定后代继承特定性状的可能性。
 
<h4>旁氏表是遗传咨询师和育种家的信息工具。</h4>
 
尽管旁氏表已经创建了100多年，但它仍然有一些相关的应用。对于接受基因咨询的夫妇来说，旁氏表可以帮助他们确定孩子患遗传性疾病的风险。例如，如果父母一方有囊性纤维化（两个隐性的，因果的等位基因），而另一方既没有也没有，他们的孩子将是携带者（即，有一个因果的等位基因），但没有囊性纤维化的风险。旁氏表还可以帮助动植物育种家选择具有特定特征的有机体继续育种。
 
尽管旁氏表在许多情况下都很有用，但它们不能准确地描述复杂的遗传。例如，由同一染色体上相邻基因编码的性状通常是从一个亲本一起遗传的，这种现象称为连锁。这些特征并不是独立分类的，因此旁氏表不能准确预测它们的遗传模式。有些特征，如身高，不适合用旁氏表，因为它们由几个基因决定，并受环境条件（如饮食）的影响。旁氏表在预测仅从一个亲本获得的性状的遗传性方面也是无效的。

Punnett 方块

概述

庞尼特方格展示了后代可能从两个亲本基因型遗传得到的基因型。如果某性状的遗传模式……

Education

教育

JoVE Core

Biology

生物学

Genetics

遗传学

Classical and Modern Genetics

经典遗传学与现代遗传学

KEY TERMS AND CONCEPTS

关键术语与概念

punnett squares for predicting traits

Punnett squares help predict which traits offspring may inherit from two parents. They show possible genotypes, which are pairs of alleles, and can also show the chance of a phenotype, or visible trait, when the inheritance pattern is known. These grids work best for traits controlled by a single gene locus and passed on independently during meiosis.

Punnett squares were developed in the early 1900s by Reginald Punnett. His work came after Gregor Mendel’s pea plant experiments revealed the basic laws of inheritance. Mendel studied traits such as pea and pod shape and color, flower color and position, and plant size. For flower color, purple and white are different traits controlled by different alleles at the same gene locus.

A Punnett square organizes genetic information in a grid. Each box represents one possible fertilization event, or one possible offspring genotype, from two parental gametes. These diagrams are often shown as 2x2 squares for one trait or 4x4 squares for two traits. Alleles are usually written with the first letter of the dominant trait. For pea color, Y stands for the dominant yellow allele, and y stands for the recessive green allele.

To build a 2x2 Punnett square, one parent’s genotype is placed across the top and the other parent’s genotype is placed down the side. One allele goes above each column, and one allele goes next to each row. The boxes then combine one allele from each parent. The full square shows the chances of each genotype and helps predict the trait an offspring may show.

Punnett squares still matter in genetics, counseling, and breeding. Genetic counselors can use them to estimate a child’s risk for inherited disease. For example, if one parent has cystic fibrosis and the other neither has nor carries it, the child will be a carrier but will not be at risk for cystic fibrosis. Breeders also use Punnett squares to choose organisms with useful traits for future breeding.

These grids do have limits. They do not work well for complex inheritance patterns, such as linked genes on the same chromosome, because those genes are not independently assorted. They are also not a good fit for traits like height, which can depend on several genes and environmental factors such as diet. Punnett squares are also not useful for traits acquired from only one parent.

Punnett Squares for Predicting Traits

genetic lingo

Genotype, Phenotype, and Inheritance

Genotype, phenotype, and inheritance help explain how traits and disease risk are passed from parents to offspring. In diploid organisms, including humans, most other animals, and many plants, somatic cells carry a duplicate set of chromosomes. These chromosome pairs are homologous, with similar length, centromere position, and gene locations. Diploid organisms inherit two versions of each gene, one from each parent. These versions are called alleles, and they sit at the same relative locus,...

punnett squares

Punnett squares help predict which traits offspring may inherit from two parents. They show possible genotypes, which are pairs of alleles, and can also show the chance of a phenotype, or visible trait, when the inheritance pattern is known. These grids work best for traits controlled by a single gene locus and passed on independently during meiosis. Punnett squares were developed in the early 1900s by Reginald Punnett. His work came after Gregor Mendel’s pea plant experiments revealed the...

monohybrid crosses

Mendel’s Pea Plant Inheritance Ratios

Gregor Mendel used pea plants to study how traits are passed from parents to offspring. His breeding experiments in the 1850s and 1860s showed that inheritance follows clear patterns. He crossed true-breeding plants that differed in one trait and found that dominant traits can hide recessive traits. Mendel focused on seven pea plant traits, and each trait had two forms controlled by a single gene locus. He noticed that true-breeding plants always produced offspring with the same phenotype, or...

dihybrid crosses

Mendel's Law of Independent Assortment

Mendel’s law of independent assortment explains how two traits can be inherited separately. Gregor Mendel tested this idea with pea plants that differed in two characteristics, such as pea color and pea shape. He used true-breeding parents that were homozygous for both traits but showed different phenotypes. In one example, Mendel crossed round, yellow peas with wrinkled, green peas. The parental generation had RRYY and rryy genotypes. Their first-generation offspring were all dihybrids,...

law of segregation

Mendel’s Pea Cross Ratios

Mendel’s pea plant crosses show how traits can disappear in one generation and return in the next. When he crossed plants, one parental trait sometimes seemed to vanish in the F1 generation and reappear in the F2 generation. Mendel used this pattern to explain why some traits are dominant and others are recessive. He proposed that traits are controlled by alleles, which are different versions of a gene. An organism inherits two copies of each gene, one from each parent. In his model, a...

law of independent assortment

Mendel’s Dihybrid Cross and Trait Ratios

Mendel’s dihybrid cross shows how two traits are inherited at the same time. A dihybrid cross is a cross in which both parents are homozygous for two distinct traits, and the F1 generation is heterozygous for both traits. Mendel used pea plants with round yellow peas and wrinkled green peas as an example. One parent had genotype YYRR, and the other had genotype yyrr. In the F1 generation, every plant showed the dominant traits, so the plants were YyRr and had yellow, round peas. The F2...

probability laws

Inheritance Risk with Sum and Product Rules

Inheritance risk can be calculated with the sum rule and the product rule. The sum rule applies to mutually exclusive events, or events that cannot happen at the same time. The product rule applies to independent events, or events that do not affect one another. These rules describe theoretical probability, which is the chance of an event before it happens. Empirical probability is different because it is based on events that have already occurred. These probability rules are useful in...

test cross

Using Test Crosses to Identify Genotypes

Test crosses are used to identify the genotype of an organism with a dominant trait. A genotype is the pair of alleles inherited for a gene, and alleles are different forms of the same gene. In diploid organisms, including humans, each gene usually has two alleles, one from each parent. An allele is recessive when its effect is hidden by another allele at the same gene location. Pea plants provide a clear example with flower color. White flowers are recessive, because one copy of the purple...

polygenic traits

Polygenic Traits in Human Height

Polygenic traits are traits controlled by more than one gene. Human height is a clear example of this kind of inheritance. Because many genes work together, the final trait can vary a lot from person to person. Researchers have found hundreds of loci, or gene locations, that influence height. There are likely many more that have not yet been identified. Many of these genes affect cartilage in the growth plates of the long bones in the arms and legs, either directly or indirectly. Height is...

pedigree analysis

Reading Family Traits in Pedigrees

Pedigrees are family trees used to track how a trait passes through generations. They help scientists and students see whether a trait is dominant or recessive, whether it is autosomal or sex-linked, what genotypes family members may have, and what phenotypes may appear in future generations. For families with a history of inherited disease, this information can be important for family planning. In plants and animals, inheritance is often studied with crosses. Monohybrid crosses can show...

multiple allele traits

Blood Type and Allele Interactions

Multiple alleles can shape traits through blood type, sickle cell anemia, incomplete dominance, and codominance. Multiple allelism means a gene has three or more allelic forms. Diploid organisms, including humans, usually carry only two alleles for each gene, but many human genes exist in multiple forms in the population. Human blood type is a clear example of multiple allelism. The blood type gene has three alleles: I A , I B , and i. These alleles help determine which blood type a person has...

epistasis

Gene Masking in Rabbit Fur Color

Epistasis describes how one gene can mask or change the effect of another gene. In high school genetics, this helps explain why many traits do not follow a simple single-gene pattern. Instead, alleles at different locations can work together to shape the final phenotype. Mendel studied seven unrelated pea traits, but most traits involve multiple gene interactions. Epistasis often happens when one gene interferes with the expression of another gene. It can also occur when genes are part of the...

nature and nurture

Genes and Environment Shape Height

Genes and environment both shape human height and other traits. Genes are the inherited instructions we get from our parents. Environment includes factors such as diet, stress, and social conditions. Many phenotypes, or observable traits, reflect both influences. Some also show up later in life, including cancer and other diseases. Height is a clear example of this interaction. Scientists estimate that 70-90% of height variation comes from genetic differences among people. The remaining 10-30%...

pleiotropy

SOX10 and Multiple Traits in Pleiotropy

Pleiotropy is when one gene affects more than one trait. The SOX10 gene is a clear example because it can influence pigmentation, hearing, and intestinal movement. These traits may seem unrelated, but they can all be linked to the same gene change. In humans, a deleted region in SOX10 can cause Waardenburg Syndrome Type 4, or WS4. WS4 is an autosomal recessive disorder, which means a person usually inherits two altered copies of the gene. Common signs include a white forelock,...

sex-linked disorders

X- and Y-Linked Disorder Patterns

X- and Y-linked disorders come from mutations in genes on the sex chromosomes. These genes, like those on autosomes, are needed for normal body function. When a mutation causes a biological problem, the condition is called sex-linked. Y-linked disorders come from changes in the Y chromosome. They affect only males, because only males carry a Y chromosome. Mutations in this small chromosome can affect male sexual function and secondary sex characteristics. One example is Y-chromosome...

x-linked traits

X-Linked Inheritance in Families

X-linked inheritance explains how traits on the X chromosome are passed through families. In most mammalian species, females have two X sex chromosomes, while males have one X and one Y. A mutation on one X chromosome may be masked in females by a normal allele on the other X. In males, that same mutation is more likely to show because there is no second normal X to balance it. Traits caused by changes on the X chromosome are called X-linked traits. Color blindness is a well-studied example.

x-inactivation

Barr Bodies and X-Chromosome Balance

Barr bodies and X-chromosome balance help explain how female mammalian cells control gene activity from the X chromosome. The human X chromosome carries far more genes than the Y chromosome. Because males usually have one X chromosome and females have two, females would make twice as many of some proteins without a control system. To prevent that imbalance, female mammalian cells inactivate nearly all the genes on one X chromosome during early embryonic development. The inactive X condenses...

non-nuclear inheritance

Maternal DNA in Mitochondria and Chloroplasts

Maternal DNA in mitochondria and chloroplasts explains how some genes are inherited outside the nucleus. Most DNA is in the nucleus, but mitochondria and chloroplasts in the cell cytoplasm also carry their own DNA and can copy it independently of nuclear DNA. Mitochondria are found in both plant and animal cells. They are called the powerhouses of eukaryotic cells because they break down glucose to make energy for cellular activity. Mitochondrial DNA has about 37 genes, and many help with...

chromosomal theory of inheritance

How Genes Map to Chromosomes

Genes map to chromosomes, and this idea explains how Mendel’s inheritance patterns work. Gregor Mendel published his pea plant breeding results in 1866. He showed that physical traits follow predictable patterns. At the time, scientists did not yet know that genes existed. Mendel used the word "factors" for the hereditary units he studied. The details behind Mendel’s laws of segregation and independent assortment were still unknown for many years. In the late 1800s, better microscopes and...

key terms and concepts

Learn how Punnett squares predict offspring genotypes and traits, from Mendel’s pea plants to genetic counseling, breeding, and simple inheritance patterns.

Punnett Squares for Predicting Traits | JoVE K12

JoVE Core series brings biology to life through over 300 concise and easy-to-understand animated video lessons that explain key concepts in biology, plus more than 150 scientist-in-action videos that show actual research experiments conducted in today’s laboratories.

biology

JoVE Core系列通过300多节动画视频课简明易懂地讲解生物学中的关键概念，以及150余段视频展示科学家在现代实验室开展实际研究实验，让生物学变得平易近人。

Next Generation Science Standards

High School

heredity-inheritance-and-variation-of-traits

Heredity: Inheritance and Variation of Traits

HS-LS3-1

new-york-state-science-learning-standards

New York State Science Learning Standards

Inheritance and Variation of Traits

HS-LS3-1.

Georgia Standards of Excellence

9-12

SB3.b

Florida Department of Education

SC.912.L.16

SC.912.L.16.1

myJoVE Corporation

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LS.10.b

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A Punnett square displays the possible genotypes offspring can inherit from two parental genotypes. If a trait&#x2019;s inheritance pattern ...

Monohybrid Crosses

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Dihybrid Crosses

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Punnett Squares for Predicting Traits

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