Name: predicting traits with punnett squares
Uploaded: 2021-04-07T12:11:58.000Z
Duration: 1 min
Channel: JoVE

K12 Standards

north-carolina-k-12-science-standard-course-of-study

North Carolina K-12 Science Standard Course of Study

9-12

Biology

heredity-inheritance-and-variation-of-traits

Heredity- Inheritance and Variation of Traits

LS.Bio.7.1

Punnett Squares

L'échiquier de Punnett, un simple diagramme nomméd'après son inventeur est une manière graphique de prédireles probabilités pour un enfant d'hériterd'un trait génétique comme l'intolérance au lactosed'après le génotype des parents. 
À partir de cette grille, les contributions génétiquesd'un parent homozygote récessifavec des allèles désignés par deux l minuscules,sont placés en haut. 
Ceux de l'autre, hétérozygote à allèles mixtes,représentés par un L majusculeet un l récessif minuscule, sont écrits à gauche. 
L'association des en-têtes des lignes et colonnespermet d'obtenir les deux génotypes possibles etles deux phénotypes d'un enfant. 
50 % de chances d'être hétérozygoteet de tolérer le lactose, et 50 % de chancesd'être homozygote récessif et intolérant au lactose.

Edwards, A. W. F. « Reginald Crundall Punnett : Premier professeur de génétique Arthur Balfour, Cambridge, 1912. » Genetics 192, no. 1 (1er septembre 2012) : 3. [<a href="https://doi.org/10.1534/genetics.112.143552 » target="__blank">Source</a>]

Reid, James B. et John J. Ross. « Les gènes de Mendel : vers une caractérisation moléculaire complète ». Genetics 189, n° 1 (1er septembre 2011) : 3. [<a href="https://doi.org/10.1534/genetics.111.132118 » target="__blank">Source</a>]

Échiquier de punnett

<h4>Aperçu</h4>
 
 Un échiquier de Punnett affiche les génotypes possibles dont la descendance peut hériter à partir de deux génotypes parentaux. Si le modèle héréditaire d’un trait (p. ex., dominant ou récessif) est connu, les échiquiers de Punnett peuvent également être utilisés pour déterminer la probabilité d’hériter un phénotype. Les échiquiers de Punnett sont applicables dans les situations où l’hérédité du trait est déterminée par un seul locus de gène et les traits sont hérités indépendamment. Cependant, ils ne peuvent pas prévoir la probabilité des traits pour des cas d’héritage génétique plus complexes. 
 
 <h4>Les échiquiers de Punnett montrent la probabilité d’hériter d’un ou de plusieurs traits</h4>
 
 Les échiquiers de Punnett sont des représentations visuelles qui montrent les génotypes possibles de la descendance résultant d’un croisement entre deux génotypes parentaux. Ils peuvent représenter la transmission d’un ou de plusieurs phénotypes, ou traits, bien que d’autres outils soient plus appropriés pour étudier la transmission de plus de deux traits.
 
 Les échiquiers de Punnett peuvent être utilisés pour déterminer la probabilité que la descendance hérite d’un génotype précis, ou d’une paire d’allèles causant une caractéristique particulière (c.-à-d. un phénotype ou trait), à condition que le phénotype soit causé par un seul locus génétique et soit assorti indépendamment pendant la méiose. En d’autres termes, les échiquiers de Punnett sont utiles pour déterminer les probabilités de transmission dans les cas de figure où la probabilité d’hériter d’un trait n’impacte pas la probabilité d’en hériter un autre. Bien qu’il existe de nombreuses exceptions à ces hypothèses (p. ex., les traits codés par des gènes voisins sur le même chromosome), ces qualificatifs sont valables pour de nombreux traits de végétaux et d’animaux.
 
 <h4>Les expériences de Mendel ont inspiré la création de l’échiquier de Punnett</h4>
 
 Les échiquiers de Punnett ont été créés au début des années 1900 par Reginald Punnett, plusieurs décennies après que les expériences révolutionnaires de Gregor Mendel sur les plants de petits pois aient révélé les lois fondamentales de l’hérédité. Aujourd’hui, les échiquiers de Punnett sont souvent utilisés pour illustrer les principes qui sont à la base des expériences de Mendel.
 
 Mendel a étudié l’hérédité de plusieurs caractéristiques de plants de petits pois, y compris la forme et la couleur des pois et des gousses, la couleur et la position de la fleur, et la taille de la plante. Mendel a également examiné les traits hérités pour chaque caractéristique. Par exemple, le violet et le blanc sont des traits possibles pour la caractéristique de couleur de la fleur. Chez les plants de petits pois, les fleurs violettes et blanches sont déterminées par des variantes génétiques distinctes, ou allèles, au locus du gène de la couleur des fleurs.
 
 <h4>Les échiquiers de Punnett sont des grilles qui organisent l’information génétique</h4>
 
 Chaque case d’un échiquier de Punnett représente un événement possible de fécondation, ou génotype de la descendance, résultant de deux gamètes parentaux. Les échiquiers de Punnett sont généralement disposés en configurations 2x2 ou 4x4 pour visualiser la transmission d’un ou deux traits, respectivement.
 
 En ce qui concerne la nomenclature, les allèles sont indiqués par la première lettre du trait causée par l’allèle dominant. Par exemple, parce que le jaune est le trait dominant de la couleur du pois, les allèles encodant la couleur du pois sont indiqués avec la lettre italique “ j ”. Les lettres en majuscules et minuscules représentent respectivement les allèles dominants et récessifs. Ainsi, J représente l’allèle jaune dominant et j dénote l’allèle vert récessif. 
 
 Pour créer un échiquier de Punnett 2x2 examinant un trait, un génotype parental est répertorié au-dessus du diagramme, avec un allèle sur chaque colonne. L’autre génotype parental est affiché verticalement à gauche du diagramme, avec un allèle à côté de chaque ligne. Chaque case d’un échiquier de Punnett contient les deux allèles parentaux (un de chaque parent) correspondant à la ligne et à la colonne de la case, représentant un résultat possible de fécondation. Le contenu complet de l’échiquier de Punnett peut être utilisé pour déterminer la probabilité que la descendance hérite d’un trait particulier. 
 
 <h4>Les échiquiers de Punnett sont des outils informatifs pour les conseillers et les éleveurs génétiques</h4>
 
 Bien qu’ils aient été créés il y a plus de 100 ans, les échiquiers de Punnett ont encore plusieurs applications pertinentes. Pour un couple recevant des conseils en génétique, les échiquiers de Punnett peuvent aider à déterminer le risque que leur enfant hérite d’une maladie. Par exemple, si l’un des parents est atteint d’une fibrose kystique (deux allèles récessifs et causals) et que l’autre ne l’a pas et ne la porte pas, leur enfant sera porteur (c.-à-d. aura un allèle causal) mais n’aura aucun risque de fibrose kystique. Les échiquiers de Punnett peuvent également aider les éleveurs d’animaux et de plantes à sélectionner des organismes ayant des caractéristiques précises pour la reproduction continue.
 
 Bien que les échiquiers de Punnett soient utiles dans de nombreux contextes, ils ne peuvent pas représenter avec précision l’héritage génétique complexe. Par exemple, les traits codés par des gènes voisins sur le même chromosome sont souvent hérités ensemble d’un parent, un phénomène nommé lien. Ces traits ne sont pas assortis indépendamment ; ainsi un échiquier de Punnett ne peut pas prévoir avec précision leurs modèles héréditaires. Certains traits, comme la hauteur, sont inappropriés pour les échiquiers de Punnett parce qu’ils sont déterminés par plusieurs gènes et influencés par les conditions environnementales (p. ex., l’alimentation). Les échiquiers de Punnett sont également inefficaces pour prévoir la transmission des traits acquis d’un seul parent.

Échiquier de Punnett

Aperçu

Un échiquier de Punnett affiche les génotypes possibles que la progéniture peut hériter de deux génotypes parentaux. Si le modèle d’hérédité d’un trait ...

Education

Enseignement

JoVE Core

Molecular Biology

Biologie moléculaire

Unit 2

Unité 2

Mendelian Genetics

La génétique mendélienne

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

predicting traits with punnett squares

Punnett squares help students predict how traits may be passed from parents to offspring. They are a simple grid used in genetics to organize possible allele combinations. An allele is a version of a gene.

The square compares the alleles each parent can give. By filling in the boxes, students can see possible genotypes, which are the genetic makeup of offspring. The results can also help connect those genotypes to traits that may appear in the next generation.

Predicting Traits with Punnett Squares

punnett squares

Punnett squares help students predict how traits may be passed from parents to offspring. They are a simple grid used in genetics to organize possible allele combinations. An allele is a version of a gene. The square compares the alleles each parent can give. By filling in the boxes, students can see possible genotypes, which are the genetic makeup of offspring. The results can also help connect those genotypes to traits that may appear in the next generation.

monohybrid crosses

Tracking One Trait in Monohybrid Crosses

Monohybrid crosses track how one trait is passed from parents to offspring. They are used to study inheritance when only a single characteristic is followed at a time. A monohybrid cross can compare the possible outcomes for a monogenic trait, which is a trait controlled by one gene. This approach helps show how one gene can shape different inherited forms of the same characteristic. The method also connects with Mendel's work on genetics. It is a useful way to predict patterns of inheritance...

dihybrid crosses

Predicting Two-Trait Genetic Crosses

Dihybrid crosses are used to predict how two traits can be passed from parents to offspring. A dihybrid cross tracks two genes at the same time, so it helps students see how different alleles can combine in a genetic pattern. This topic is closely tied to Mendelian genetics and independent assortment. Independent assortment means that allele pairs for different traits can separate into gametes independently of one another. When students work through a dihybrid cross, they can compare the...

trihybrid crosses

Forked Line Method for Trihybrid Crosses

Forked line method for trihybrid crosses helps predict the outcome of three-trait Mendelian crosses. A trihybrid cross studies three pairs of contrasting characteristics. It combines three separate monohybrid crosses. Common examples include plant height, seed shape, and seed color. In a typical trihybrid cross, the F1 plants are heterozygous for all three traits. They can produce eight different gametes. After self-fertilization, these gametes can lead to 64 genotype combinations in the F2...

law of independent assortment

Independent Chromosome Assortment in Meiosis

Independent chromosome assortment in meiosis explains how different gene pairs can be inherited independently. This idea is one of Mendel’s laws of inheritance and is often called the law of independent assortment. The pattern depends on how homologous chromosomes line up during meiosis I. Each chromosome pair orients independently of the others, so the maternal and paternal chromosomes can separate into different gametes in many combinations. This random separation helps create genetic...

chi-square analysis

Chi-Square Test in Genetics

The chi-square test in genetics helps compare expected and observed results. It is a statistical hypothesis test used to see whether a difference between an expected value and an observed value is significant. In genetics, it helps decide whether to accept or reject a hypothesis based on how far the observed data moves from the expected data. The test was developed by Pearson in 1990. The first step is to set up a null hypothesis. This hypothesis says there is no real difference between the...

pedigree analysis

Tracing Traits with Pedigree Charts

Pedigree analysis uses family trees, called pedigrees, to trace how traits and diseases pass from one generation to the next. A pedigree chart helps scientists and students see inheritance patterns clearly across relatives. The chart uses standard symbols to show family members and their relationships. It can reveal whether a trait is likely passed through dominant or recessive inheritance, and it can also help identify patterns linked to sex chromosomes. By studying a pedigree, it is...

multiple allele traits

Multiple Alleles in Trait Inheritance

Multiple alleles can shape how a trait is inherited in a population. A gene may have more than two allele forms, even though each person still carries only two alleles for that gene. These allele combinations can produce traits with more than two possible outcomes. The ABO blood group system is a common example of a multiple allele trait. It shows how different alleles can interact to determine an organism’s phenotype, or observable trait. Multiple allele traits help explain why inheritance...

incomplete dominance

Incomplete Dominance in Traits and Disease

Incomplete dominance is a pattern of inheritance where two alleles both affect a trait in a heterozygous organism. In this case, one allele is not fully dominant over the other. The result is a phenotype that looks like a blend or intermediate form. Gregor Mendel’s pea plant experiments helped explain the usual dominant and recessive pattern. He showed that each gene in a diploid cell has two alleles, one inherited from each parent. In his model, a dominant allele shows its effect with one or...

lethal alleles

When Genes Cause Embryonic Death

Lethal alleles can change inheritance patterns by causing death before birth. In mice, Lucien Cuénot studied the agouti gene, which helps control coat color through an agouti-signaling protein that affects melanin distribution in mammals. The wild-type allele produces a gray-brown coat, while the mutant allele produces a yellow coat. Cuénot also found that the yellow allele was linked to yellow mouse obesity syndrome. This syndrome is associated with early-onset obesity and tumors. When he...

polygenic traits

Traits Shaped by Many Genes

Polygenic traits are characteristics shaped by many genes acting together. This pattern is different from a single-gene trait, where one gene has a larger effect on the outcome. In polygenic inheritance, each gene adds a small contribution to the final trait. Height is a common example of a polygenic trait. Many genes influence human height, so the result can vary across a wide range. These small genetic effects combine to produce differences that are easy to see in a population. Polygenic...

background and environment affect phenotype

background-and-environment-affect-phenotype

How Genes and Environment Shape Traits

Genes and the environment work together to shape phenotype, or the visible traits of an organism. A phenotype can change because of genetic background, environmental conditions, or both. Factors such as temperature, oxygen availability, and mutagens can all influence how a trait appears. Horses show how one gene can affect coat color and how a modifier gene can change that result. The Extension gene controls pigment production in the coat. The wild-type genotype EE produces black pigment,...

x and y chromosomes

Sex Chromosomes in Human Inheritance

Sex chromosomes help determine biological sex in mammals, including humans. Humans have two sex chromosomes, X and Y. Each diploid cell has 22 pairs of autosomes and one pair of sex chromosomes. A female usually has two X chromosomes, while a male usually has one X chromosome and one Y chromosome. Egg and sperm cells carry only half the usual number of chromosomes. They contain 22 autosomes and one sex chromosome. Every egg has an X chromosome. Sperm cells can carry either an X or a Y...

the y chromosome determines maleness

Y Chromosome Structure and Male Traits

The Y chromosome is a sex chromosome that helps guide male development in humans and other vertebrates and mammals. Human males usually have one X chromosome and one Y chromosome, along with 22 pairs of autosomes. In these organisms, the presence or absence of the Y chromosome influences whether male traits develop. The Y chromosome evolved from an autosome about 300 million years ago, when two sex chromosomes began to diverge. Since then, it has lost most of its genes and become much smaller.

the ratio of x chromosome to autosomes

Drosophila Sex Determination by X:A Balance

In Drosophila, sex is determined by the balance between X chromosomes and autosomes, not by the X and Y chromosomes alone. The Y chromosome is active in these flies, but it does not set sex. Instead, it carries genes needed for sperm production in adult males. A normal male Drosophila has one X chromosome and two sets of autosomes. A normal female has two X chromosomes and two sets of autosomes. When this X:A ratio changes, flies can develop different sexual phenotypes, including metamales,...

x-linked traits

X-Linked Inheritance in Families

X-linked inheritance in families explains how traits linked to the X chromosome pass from parents to children. These traits are often tracked through family trees because the pattern can differ between males and females. A male has one X chromosome and one Y chromosome. A female has two X chromosomes. Because of this difference, a trait on the X chromosome can show up in a different way depending on the sex of the child. Family examples often include traits such as color blindness. Studying...

sex linked disorders

Sex-Linked Disorders and Inheritance Patterns

Sex-linked disorders are genetic conditions that follow inheritance patterns tied to the sex chromosomes. These disorders help explain how certain traits can appear more often in one sex than the other. The transcript focuses on examples of sex-linked disorders, including Y-linked infertility, Fragile X syndrome, and Duchenne muscular dystrophy. Y-linked infertility is passed through the Y chromosome, while Fragile X syndrome and Duchenne muscular dystrophy are associated with sex-linked...

dosage compensation

X-Chromosome Balance in Animals

X-chromosome balance in animals helps equalize gene expression between males and females. Sex can be determined by the number and type of sex chromosomes. In humans, females have two X chromosomes and males have one X and one Y chromosome. In C. elegans, one X chromosome is male, while two X chromosomes make a hermaphrodite. The X chromosome carries more than sex-related genes. It also includes genes involved in body functions such as brain development and the immune system. Because males and...

x-inactivation

X-Inactivation and Barr Bodies

X-inactivation is a process that reduces gene activity on one X chromosome. It helps balance gene expression in cells that have more than one X chromosome. A key result of this process is the formation of a Barr body, which is the inactive X chromosome seen in the nucleus. This topic also includes Xist, a gene linked to X-inactivation. Xist produces RNA that coats the X chromosome and helps turn it off. Together, Xist and the Barr body show how cells control X-linked genes during development...

blood types

Blood Types and Transfusion Matching

Human blood types help determine safe blood transfusion matching. Blood is classified by antigens on the surface of red blood cells and antibodies in the plasma. Correct blood typing matters because an unsafe match can affect transfusion success. The International Society of Blood Transfusion has identified 38 human blood types, and ABO, Rh, and MNS are among the most common. The ABO blood group depends on antigens made by genes on chromosome 9. Red blood cells carry a base glycoprotein called...

blood transfusion and agglutination

Matching Blood Types for Safe Transfusion

Blood transfusion is a medical treatment used to restore blood volume after major blood loss from an accident or a medical procedure. It works by taking blood from a suitable donor and giving it to a recipient. Safe transfusion depends on matching blood types and checking for immune compatibility. The history of blood transfusion began in the 17th century, when early experiments were done in animals. In 1818, James Blundell, a British doctor, performed the first successful human blood...

key terms and concepts

Learn how Punnett squares help predict allele combinations, genotypes, and possible traits passed from parents to offspring in genetics.

Predicting Traits with Punnett Squares | JoVE K12

molecular biology

JoVE Core Biologie Moléculaire illustre les processus moléculaires au sein de la cellule grâce à des leçons vidéos claires et concises. Les applications de ces concepts sont ensuite démontrées grâce à des expériences concrètes en laboratoire.

Louisiana Student Standards for Science

High School

Life Sciences

Heredity: Inheritance And Variation Of Traits

HS-LS3-1

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

Heredity

Structure and function of DNA in cells

Genetic mechanisms and inheritance

Alabama Course of Study Science

Heredity: Inheritance and Variation of Traits

9-12.B.3.11.a

Texas Essential Knowledge and Skills

BIO.8

BIO.8.B

myJoVE Corporation

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Meiosis II

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Use models to explain how DNA is passed from parents to offspring through the processes of meiosis and fertilization in sexual reproduction.

LS.Bio.6.1

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The Replisome

Proofreading

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Replication in Eukaryotes

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Fixing Double-strand Breaks

Homologous Recombination

Gene Conversion

Restarting Stalled Replication Forks

Construct an explanation to summarize how inheritable genetic variations may result from: new genetic combinations in meiosis, mutations during replication, or mutations caused by environmental factors.

LS.Bio.6.2

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Genetic Crosses

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Monohybrid Crosses

Dihybrid Crosses

Trihybrid Crosses

Trihybrid Crosses
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Law of Independent Assortment

Chi-square Analysis

The chi-square test is a statistical hypothesis test. It is used to check whether there is a significant difference between an expected value and an ...

Pedigree Analysis

Multiple Allele Traits

Incomplete Dominance

Gregor Mendel&#39;s work (1822 - 1884) was primarily focused on pea plants. Through his initial experiments, he determined that every gene in a diploid ...

Lethal Alleles

Agouti: A Lethal Allele
Lucien Cu&#233;not discovered lethal alleles in 1905 while studying the inheritance of coat color in mice. The agouti gene is ...

Polygenic Traits

Background and Environment Affect Phenotype

Although the genetic makeup of an organism plays a major role in determining the phenotype, there are also several environmental factors, such as ...

Use mathematics and computational thinking to predict the variation and distribution of expressed traits based on: Mendelian inheritance, co-dominance, incomplete dominance, multiple alleles, and sex-linked inheritance.

Overview

A pedigree is a diagram displaying a family&#x2019;s history of a trait. Analyzing pedigrees can reveal (1) whether a trait is dominant or ...

Probability Laws

Overview

The probability of inheriting a trait can be calculated using the sum and product rules. The sum rule is used to calculate the probability of ...

The Concept of Multiple Allelism

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Analyze and interpret data to explain how polygenic traits result in a wide range of phenotypes.

LS.Bio.7.2

Pleiotropy

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Nature and Nurture

Many human characteristics, like height, are shaped by both nature&mdash;in other words, by our genes&mdash;and by nurture, or our environment. For ...

Construct an explanation to summarize how traits result from interactions of genetic factors (multiple genes and/or alleles) and environmental factors.

LS.Bio.7.3

Understand genetic mechanisms for variation.

Predicting Traits with Punnett Squares

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