Name: test cross in genetic inheritance
Uploaded: 2021-04-07T12:12:00.000Z
Duration: 1 min 50 s
Channel: JoVE

- Een testkruis is een techniek die kan worden gebruikt om het geno-type te bepalen van een organisme dat een dominante eigenschap vertoont, zoals paarse bloemkleur bij erwtplanten.
 Omdat de dominante versie, of allel van een gen, altijd zal worden uitgedrukt over het recessieve allel, zullen organismen met het homozygote dominante geno-type, twee dominante allelen, hetzelfde lijken als organismen met het heterozygote geno-type, &#xE9;&#xE9;n dominant allel.
 Een paarsbloemige erwtenplant van onbekend geno-type kan worden gekruist naar een erwtenplant die het recessieve feno-type heeft, witte bloemen, en dus bekend is dat het homozygoot recessieve geno-type, kleine p, kleine p.
In &#xE9;&#xE9;n scenario, als alle nakomelingen van het testkruis het dominante fenotype vertonen, moet de onbekende ouder homozygoot dominant zijn voor paarse bloemen.
 Alle nakomelingen zijn heterozygoot, en ontvangen &#xE9;&#xE9;n recessief allel van de recessieve ouder, en &#xE9;&#xE9;n dominant allel van de andere ouder.
 Als de nakomelingen echter gelijke aantallen bevatten van organismen die het dominante fenotype vertonen, en organismen die het recessieve fenotype vertonen, moet de onbekende ouder heterozygoot zijn.
Alle nakomelingen ontvingen nog steeds hun recessieve allel van de recessieve ouder, de helft van de nakomelingen ontving een dominant allel van de heterozygote ouder en vertonen de dominante fenotype, terwijl de andere helft een tweede exemplaar ontving van het recessieve allel van de heterozygote ouder, en vertonen het recessieve fenotype.

test cross

Test Cross

Allelen zijn verschillende vormen van hetzelfde gen. Mensen en andere diplo&#xEF;de organismen erven van elk gen twee allelen, &#xE9;&#xE9;n van elke ouder.

Een allel is recessief als de effecten ervan worden gemaskeerd door een ander allel op dezelfde genlocatie. Erwtenplanten kunnen bijvoorbeeld paarse of witte bloemen hebben. In dit geval zijn witte bloemen recessief, aangezien een enkele kopie van het allel voor paarse bloemen resulteert in een plant met paarse bloemen, zelfs als deze ook het allel voor witte bloemen heeft.

Als een organisme een bekende recessieve eigenschap vertoont, is het bepalen van het genotype van het organisme&#x2014;het paar erfelijke allelen&#x2014;eenvoudig. Slechts &#xE9;&#xE9;n genotype, pp (twee recessieve allelen), produceert witte bloemen.

Voor een organisme met een dominante eigenschap &#x2013; zoals een erwtenplant met paarse bloemen &#x2013; is het bepalen van het genotype niet zo eenvoudig. Twee genotypen, PP en Pp, produceren paarse bloemen.

Wetenschappers gebruiken testkruisingen om de genotypen te bepalen van organismen die eenvoudige dominante eigenschappen vertonen. Bij een testkruising gaat het om het fokken of kruisen van het organisme in kwestie met een organisme dat de recessieve tegenhanger van zijn dominante eigenschap vertoont.

In een proefkruising voor een erwtenplant met paarse bloemen wordt de plant veredeld met een erwtenplant met witte bloemen (ppgenotype). De bloemkleur van de resulterende nakomelingen laat zien of de ouder met paarse bloemen homozygoot (PP) of heterozygoot (Pp).

Als de plant homozygoot is, erven alle nakomelingen een van de dominante P-allelen en een van de recessieve Pallelen van de andere ouder. Omdat dominante allelen recessieve allelen maskeren, zullen alle nakomelingen paarse bloemen hebben, de dominante eigenschap.

Als de plant echter heterozygoot is, erft ongeveer 50% van de nakomelingen het recessieve Pallel, samen met een ander recessief allel van de andere ouder. Daarom zal ongeveer de helft van de nakomelingen uit dit kruis witte bloemen hebben. Op deze manier kunnen testkruisingen onbekende ouderlijke genotypen onthullen.

Alleles are different forms of the same gene. Humans and other diploid organisms inherit two alleles of every gene, one from each parent.

An allele is ...

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Education

JoVE Core

Molecular Biology

Moleculaire biologie

Unit 2

Onderdeel 2

Analyzing Gene Expression and Function

Analyse van genexpressie en functie

KEY TERMS AND CONCEPTS

BELANGRIJKE TERMEN EN CONCEPTEN

Test Kruising

test cross in genetic inheritance

A test cross is a genetics tool used to determine the genotype of an organism with a dominant trait. It helps reveal whether the dominant individual is homozygous or heterozygous by crossing it with a recessive individual.

The outcome of the cross shows the hidden genotype. If any offspring show the recessive trait, the dominant parent must carry one recessive allele. If all offspring show the dominant trait, the dominant parent is likely homozygous dominant.

Test crosses are common in basic inheritance studies. They help students connect visible traits to the alleles behind them and make predictions about offspring using simple genetic crosses.

Test Cross in Genetic Inheritance

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A test cross is a genetics tool used to determine the genotype of an organism with a dominant trait. It helps reveal whether the dominant individual is homozygous or heterozygous by crossing it with a recessive individual. The outcome of the cross shows the hidden genotype. If any offspring show the recessive trait, the dominant parent must carry one recessive allele. If all offspring show the dominant trait, the dominant parent is likely homozygous dominant. Test crosses are common in basic...

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key terms and concepts

Learn how a test cross reveals whether a dominant organism is homozygous or heterozygous by crossing it with a recessive individual and checking offspring traits.

Test Cross in Genetic Inheritance | JoVE K12

molecular biology

JoVE Core Molecular Biology showcases the molecular processes of the cell through clear and concise animated video lessons. Additionally, in scientist-in-action videos, these concepts' application is demonstrated through real experiments in modern laboratories.

Test Cross in Genetic Inheritance

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