Name: predicting two-trait genetic crosses
Uploaded: 2021-04-07T12:11:58.000Z
Duration: 1 min 18 s
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

Dihybrid Crosses

- [Instructeur] Avec les plants de pois,Gregor Mendel a aussi réalisé des croisements dihybrides,des expériences de croisements entre des organismesqui varient par deux traits,comme la forme et la couleur des graines. 
Par exemple, si un parent est homozygote dominantpour des graines rondes et jaunes,et que l'autre est homozygote récessifpour des graines ridées et vertes,toutes les plantes de la génération F1 sont dihybrides,soit hétérozygotes pour deux traits. 
Les plantes F1 possèdent le phénotype dominantpour les deux traits et ont des graines rondes et jaunes. 
Après autofécondation, leur descendance, la génération F2,comporte des plantes aux graines rondes et jaunes,rondes et vertes, ridées et jauneset ridées et vertesavec un ratio de 9:3:3:1. 
Notablement, le rapport des grainesrondes et ridées et des graines jaunes et vertesest à chaque fois de 3:1. 
Ces traits se sont donc séparés indépendamment,ce qui démontre le principe de ségrégation indépendante.

Clancy, Suzanne. 2008. « Recombinaison génétique ». Éducation à la nature 1 (1) : 40. [<a href="https://www.nature.com/scitable/topicpage/genetic-recombination-514 » target="__blank">Source</a>]

Lobo, Ingrid et Kenna Shaw. 2008. « Découverte et types de liens génétiques. » Éducation à la nature 1 (1) : 139. [<a href="https://www.nature.com/scitable/topicpage/discovery-and-types-of-genetic-linkage-50 » target="__blank">Source</a>]

Miko, Ilona. 2008. « Gregor Mendel et les principes de l’hérédité ». Éducation à la nature 1 (1) : 134. [<a href="https://www.nature.com/scitable/topicpage/gregor-mendel-and-the-principles-of-inheritance-593 » target="__blank">Source</a>]

croisement d'hybrides

<h4>Aperçu</h4>
 
 Pour déterminer si les traits sont hérités ensemble ou séparément, Gregor Mendel a croisé des plants de petits pois qui différaient en deux traits. Ces plants parentaux étaient homozygotes pour les deux traits mais affichaient des phénotypes différents. Les descendants de la première génération étaient tous des dihybrides, des hétérozygotes présentant les deux phénotypes dominants. Lorsqu’ils étaient autofécondés, les dihybrides ont constamment produit une descendance avec un rapport de 9:3:3:1 de quatre combinaisons possibles de phénotype. Ce rapport suggérait que le fait d’hériter d’un trait n’impactait pas la probabilité d’hériter de l’autre, établissant la loi de Mendel sur l'assortiment indépendant.
 
 <h4>Les croisements dihybrides de Mendel démontrent le principe de l'assortiment indépendant</h4>
 
 Les croisements monohybrides de Gregor Mendel, entre les plants de petits pois qui différaient d’un seul trait, ont démontré que (1) les organismes héritent au hasard d’une des deux copies de chaque gène de chaque parent (la première loi de Mendel de ségrégation), et (2) l’allèle dominant peut masquer les effets de l’allèle récessif sur le phénotype (le principe d’uniformité).
 
 Pour déterminer si deux traits sont hérités séparément ou ensemble, Gregor Mendel a aussi effectué des croisements avec des plants qui différaient en deux traits, tels que la couleur des pois et la forme des pois. Pour ces croisements dihybrides, Mendel a d’abord accouplé des plantes qui étaient des variétés pures (c.-à-d. homozygotes) pour des traits différents des deux mêmes caractéristiques. Par exemple, il a croisé des plants qui étaient des variétés pures de pois ronds et jaunes (génotype RRJJ) avec ceux qui étaient des variétés pures de pois ridés et verts (génotyperryy). Cette génération parentale (P0) a produit des descendants (génération F1) qui étaient tous hétérozygotes avec des phénotypes dominants. Ces dihybrides avaient des génotypes RrJj et des pois ronds et jaunes.
 
 Mendel a ensuite induit l’autopollinisation dans les dihybrides F1. Sur les seize combinaisons possibles d’allèles parentaux, neuf produisent des descendants aux traits dominants, les pois jaunes et ronds. Six événements de fécondation confèrent un trait dominant, avec trois produisant des pois jaunes (dominants) ridés, et trois créant des pois ronds (dominants) et verts. La seule possibilité restante se traduit par des pois verts et ridés, les deux phénotypes récessifs.
 
 La proportion de phénotypes observés par Mendel chez les plants F2 était constamment similaire à ce rapport de 9:3:3:1, qui n’est attendu que si chaque fécondation est tout aussi probable. Ainsi, l’observation de ce rapport phénotypique suggère qu’hériter d’un de ces traits (p. ex., la couleur jaune ou verte du pois) n’influe pas sur la probabilité d’hériter de l’un des autres (p. ex., des pois ronds ou ridés). Cette conclusion est le nœud de la deuxième loi de Mendel, le principe (ou la loi) de l'assortiment indépendant.
 
 <h4>Le lien et la recombinaison influencent la co-hérédité des traits</h4>
 
 Les gènes sur des chromosomes distincts et non homologues sont assortis dans les gamètes de façon indépendante pendant la méiose. Cependant, les gènes proches les uns des autres sur le même chromosome sont plus susceptibles d’être répartis dans les mêmes gamètes, un phénomène nommé lien. Ainsi, hériter d’un trait peut être lié à la probabilité d’hériter d’un autre trait. Mendel n’a jamais rapporté le lien, bien que tous les traits qu’il a étudiés ne soient pas déterminés par des locus sur des chromosomes différents.
 
 Les allèles déterminant la couleur des gousses et la forme du pois sont sur les chromosomes 5 et 7, respectivement, et sont donc sans lien. Pour la plupart des autres traits, l’absence de lien peut être expliquée par la recombinaison, qui peut causer les modèles héréditaire des gènes sur le même chromosome pour imiter l'assortiment indépendant. Pendant la prophase I de la méiose, les paires de chromosomes s’alignent, se croisent et échangent des segments génétiques homologues, un processus connu sous le nom de recombinaison. Plus les deux locus sont proches l’un de l’autre sur un chromosome, plus ils sont susceptibles d’être sur le même segment recombiné et donc hérités ensemble. De même, les locus qui sont très éloignés sont plus susceptibles d’être hérités séparément en raison d’un plus grande nombre d’événements de recombinaison qui les divisent. 
 
 Pour retourner aux traits de Mendel, la couleur des pois et des fleurs est déterminée par deux locus du chromosome 1 qui sont éloignés les uns des autres. De même, le locus pour la position de la fleur est loin des autres locus du chromosome 4, la forme des gousses et la hauteur des plants. En raison de la recombinaison, il n’est pas surprenant que le lien ne se soit jamais manifesté dans ces croisements. Les locus quant à la forme des gousses et la hauteur des plants, cependant, sont assez proches les uns des autres sur le chromosome 4 pour qu’un certain lien soit probable. Mendel n’a jamais publié les résultats de ce croisement particulier ; il est donc possible qu’il n’ait tout simplement jamais effectué ces expériences, ce qui fait qu’il lui manquait un croisement pour découvrir le lien.

Croisement d'hybrides

Aperçu

Pour déterminer si les caractères sont hérités ensemble ou séparément, Gregor Mendel a croisé des plants de pois qui différaient par deux caractères. Ces ...

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 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 possible offspring outcomes for both traits together.

Dihybrid crosses are a useful way to practice Punnett square skills and understand inheritance across generations. They also help show why some offspring combinations appear more often than others. For high school biology, this makes dihybrid crosses an important part of learning how traits are inherited.

Predicting Two-Trait Genetic Crosses

punnett squares

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.

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

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

Explore dihybrid crosses through Mendelian genetics and independent assortment. See how two traits are tracked together to predict offspring inheritance.

Predicting Two-Trait Genetic Crosses | 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

Florida Department of Education

Life Science

SC.912.L.16

SC.912.L.16.2

Texas Essential Knowledge and Skills

BIO.8

BIO.8.B

myJoVE Corporation

What is Meiosis?

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Meiosis I

Meiosis II

Meiosis vs. Mitosis

Crossing Over

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Nondisjunction

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Spermatogenesis

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Oogenesis

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Fertilization

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Cleavage and Blastulation

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Gastrulation

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Neurulation

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Cell Migration

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Determination

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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

Mutations

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Genome Size and the Evolution of New Genes

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Types of Genetic Transfer Between Organisms

Base-pairing and DNA Repair

The DNA Replication Fork

Lagging Strand Synthesis

The Replisome

Proofreading

Synthesis of new DNA molecules is carried out by the enzyme DNA polymerase, which adds nucleotides on the daughter strand complementary to the template ...

Replication in Prokaryotes

DNA replication has three main steps: initiation, elongation, and termination. Replication in prokaryotes begins when initiator proteins bind to the ...

Replication in Eukaryotes

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Overview of DNA Repair

Base Excision Repair

Nucleotide Excision Repair

DNA Distortion and Damage
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Mismatch Repair

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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

An Overview of Genetic Analysis

An organism&#8217;s physical traits, or phenotype, are a product of its genotype, which is the combination of alleles (gene variants) inherited from its ...

Genetic Crosses

To dissect genetic processes or create organisms with novel suites of traits, scientists can perform genetic crosses, or the purposeful mating of two ...

Punnett Squares

Monohybrid Crosses

Trihybrid Crosses

Trihybrid Crosses
Some of Mendel&#8217;s crosses examined three pairs of contrasting characteristics. Such a cross is called a trihybrid cross. A ...

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

Multiple allelism describes genes that exist in three or more allelic forms. Although diploid organisms, like humans, ...

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

LS.Bio.7.2

Pleiotropy

Pleiotropy is the phenomenon in which a single gene impacts multiple, seemingly unrelated phenotypic traits. For example, defects in the SOX10 gene cause ...

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 Two-Trait Genetic Crosses

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