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

Eine Testkreuzung ist eine Technik, die zur Bestimmung des Genotyps eines Organismus, der ein dominantes Merkmal zeigt, verwendet werden k&#xF6;nnen.
 Zum Beispiel eine violettbl&#xFC;tige Erbsenpflanze.
 Weil die dominante Version oder das Allel eines Gens immer &#xFC;ber das rezessive Allel ausgedr&#xFC;ckt wird, sehen Organismen mit dem homozygoten-dominanten Genotyp und zwei dominanten Allele gleich aus wie Organismen mit dem heterozygoten Genotyp, einem dominanten Allel.
 Eine violettbl&#xFC;tige Erbsenpflanze mit unbekanntem Genotyp kann mit einer Erbsenpflanze gekreuzt werden, die den rezessive Ph&#xE4;notyp hat, wei&#xDF;e Bl&#xFC;ten.
 Und man wei&#xDF;, dass sie den homozygot-rezessive Genotyp hat, klein p, klein p.
 In einem Szenario, in dem alle Nachkommen aus der Testkreuzung den dominanten Ph&#xE4;notyp zeigen, muss das unbekannte Elternteil homozygot-dominant f&#xFC;r violette Bl&#xFC;ten sein.
 Alle Nachkommen sind heterozygot, sie erhalten ein rezessives Allels des rezessiven Elternteils und ein dominantes Allel des anderen Elternteils.
 Wenn die Nachkommen aber die gleiche Zahl Nachkommen haben, die den dominanten Ph&#xE4;notyp zeigen, und Nachkommen, die den rezessiven Ph&#xE4;notyp aufweisen, muss der unbekannte Elternteil heterozygot sein.
 Alle Nachkommen erhalten ihr rezessives Allel vom rezessiven Elternteil.
 Die H&#xE4;lfte der Nachkommen erh&#xE4;lt ein dominantes Allel vom heterozygoten Elternteil und zeigen den dominanten Ph&#xE4;notyp, w&#xE4;hrend die andere H&#xE4;lfte eine zweite Kopie des rezessiven Allels des heterozygoten Elternteil erh&#xE4;lt und den rezessiven Ph&#xE4;notyp zeigt.

Miko, Ilona. 2008. "Testkreuze." Naturerziehung 1 (1): 136. [<a href="https://www.nature.com/scitable/topicpage/test-crosses-585">Quelle</a>]

Reid, James B. und John J. Ross. 2011. "Mendels Gene: Auf dem Weg zu einer vollständigen molekularen Charakterisierung" Genetik 189 (1): 3–10. [<a href="https://doi.org/10.1534/genetics.111.132118">Quelltext</a>]

kreuz testen

Test Cross

Allele sind verschiedene Formen des gleichen Gens. Der Mensch und andere diploide Organismen erben zwei Allele jedes Gens, jeweils eines von jedem Elternteil.
 
 Ein Allel ist rezessiv, wenn seine Wirkungen durch ein anderes Allel am gleichen Genlocus verdeckt werden. Zum Beispiel k&#xF6;nnen Erbsenpflanzen violette oder wei&#xDF;e Bl&#xFC;ten haben. In diesem Beispiel sind wei&#xDF;e Bl&#xFC;ten rezessiv, da eine einzelne Kopie des Allels f&#xFC;r violette Bl&#xFC;ten zu einer Pflanze mit violetten Bl&#xFC;ten f&#xFC;hrt, auch wenn diese Pflanzen das Allel f&#xFC;r wei&#xDF;e Bl&#xFC;ten haben.
 
 Wenn ein Organismus ein bekanntes rezessives Merkmal aufweist, ist die Bestimmung des Genotyps des Organismus und des Paares der vererbten Allele einfach. Nur ein Genotyp, pp (zwei rezessive Allele), produziert wei&#xDF;e Bl&#xFC;ten.
 
 F&#xFC;r einen Organismus mit einem dominanten Merkmal wie eine Erbsenpflanze mit violetten Bl&#xFC;ten ist die Bestimmung des Genotyps nicht so leicht. Zwei Genotypen, PP und Pp, k&#xF6;nnen violette Bl&#xFC;ten produzieren.
 
 Wissenschaftler f&#xFC;hren Testkreuzungen durch, um die Genotypen von Organismen zu bestimmen, die einfache dominante Merkmale aufweisen. Bei einer Testkreuzung wird der zu bestimmende Organismus mit einem Organismus gez&#xFC;chtet oder gekreuzt, der das rezessive Gegenst&#xFC;ck des dominanten Merkmals aufweist.
 
 Bei einer Testkreuzung f&#xFC;r eine Erbsenpflanze mit violetten Bl&#xFC;ten wird mit einer Erbsenpflanze mit wei&#xDF;en Bl&#xFC;ten (pp-Genotyp) gekreuzt. Die Bl&#xFC;tenfarbe der entstehenden Nachkommen zeigt, ob der Elternteil mit violetten Bl&#xFC;ten homozygot (PP) oder heterozygot (Pp) ist.
 
 Wenn die Pflanze homozygot ist, erben alle Nachkommen eines ihrer dominanten P-Allele und eines der anderen rezessiven P-Allele der Eltern. Da das dominante Allel das rezessive Allele verdeckt, haben alle Nachkommen violette Bl&#xFC;ten, das dominante Merkmal.
 
 Wenn die Pflanze jedoch heterozygot ist, erben etwa 50% der Nachkommen ihr rezessives p-Allel, zusammen mit einem weiteren rezessiven Allel von dem anderen Elternteil. Daher wird etwa die H&#xE4;lfte der Nachkommen aus dieser Kreuzung wei&#xDF;e Bl&#xFC;ten haben. Auf diese Weise kann man durch Testkreuzungen unbekannte elterliche Genotypen bestimmen.

Kreuz testen

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

Lehre

JoVE Core

Molecular Biology

Molekularbiologie

Unit 2

Einheit 2

Analyzing Gene Expression and Function

Analyse von Genexpression und -funktion

KEY TERMS AND CONCEPTS

KERNBEGRIFFE UND KONZEPTE

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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test cross

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 veranschaulicht die molekularen Prozesse der Zelle in prägnanten animierten Video-Lektionen. In Videos von Wissenschaftlern in Aktion wird die Anwendung dieser Konzepte zusätzlich durch reale Experimente in modernen Laboren demonstriert.

Test Cross in Genetic Inheritance

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