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

- Um teste cruzado &#xE9; uma t&#xE9;cnica que pode ser usada para determinar o gen&#xF3;tipo de um organismo, expressando um tra&#xE7;o dominante, como, a cor da flor roxa em plantas de ervilha. 
Porque a vers&#xE3;o dominante, ou alelo, de um gene sempre ser&#xE1; expressa sobre o alelo recessivo, organismos com o gen&#xF3;tipo homozig&#xF3;tico dominante, dois alelos dominantes aparecer&#xE3;o da mesma forma como organismos com o gen&#xF3;tipo heterozig&#xF3;tico, um alelo dominante. 
Uma planta de ervilha de flor roxa de gen&#xF3;tipo desconhecido pode ser cruzada com uma planta de ervilha com o fen&#xF3;tipo recessivo e flores brancas. 
Assim, conhecida pelo gen&#xF3;tipo homozigoto-recessivo, p pequeno, p pequeno. 
Em um cen&#xE1;rio, se todos os descendentes do teste cruzado exibirem o fen&#xF3;tipo dominante, o pai desconhecido deve ser homozigoto dominante para flores roxas. 
Todos os filhos s&#xE3;o heterozigotos, recebendo um alelo recessivo do pai recessivo, e um alelo dominante do outro progenitor. 
No entanto, se os descendentes inclu&#xED;rem n&#xFA;meros iguais de organismos, exibindo o fen&#xF3;tipo dominante, e organismos exibindo o fen&#xF3;tipo recessivo, o pai desconhecido deve ser heterozig&#xF3;tico. 
Todos os filhos ainda recebem seu alelo recessivo, do pai recessivo. 
Metade dos descendentes receberam um alelo dominante do pai heterozigoto e exibem o fen&#xF3;tipo dominante, enquanto a outra metade recebeu uma segunda c&#xF3;pia do alelo recessivo do genitor heterozigoto, e exibe o fen&#xF3;tipo recessivo.

Miko, Ilona. 2008. "Cruzes de teste." Educação da Natureza 1 (1): 136. [<a href="https://www.nature.com/scitable/topicpage/test-crosses-585">Fonte</a>]

Reid, James B. e John J. Ross. 2011. "Genes de Mendel: Rumo a uma Caracterização Molecular Completa" Genética 189 (1): 3–10. [<a href="https://doi.org/10.1534/genetics.111.132118">Fonte</a>]

cruzamento teste

Test Cross

Alelos s&#xE3;o formas diferentes do mesmo gene. Humanos e outros organismos dipl&#xF3;ides herdam dois alelos de cada gene, um de cada progenitor.
 
 Um alelo &#xE9; recessivo se os seus efeitos forem mascarados por outro alelo no mesmo local gen&#xE9;tico. Por exemplo, plantas de ervilha podem ter flores roxas ou brancas. Neste caso, as flores brancas s&#xE3;o recessivas, uma vez que uma &#xFA;nica c&#xF3;pia do alelo para flores roxas resultar&#xE1; em uma planta com flores roxas, mesmo que ela tamb&#xE9;m tenha o alelo para flores brancas.
 
 Se um organismo exibe uma caracter&#xED;stica recessiva conhecida, determinar o gen&#xF3;tipo do organismo&#x2014;o seu par de alelos herdados&#x2014;&#xE9; simples. Apenas um gen&#xF3;tipo, pp (dois alelos recessivos), produz flores brancas.
 
 Para um organismo com uma caracter&#xED;stica dominante&#x2014;como uma planta de ervilha com flores roxas&#x2014;determinar o gen&#xF3;tipo n&#xE3;o &#xE9; t&#xE3;o simples. Dois gen&#xF3;tipos, PP e Pp, produzem flores roxas.
 
 Os cientistas usam cruzamentos de teste para determinar os gen&#xF3;tipos de organismos que exibem caracter&#xED;sticas dominantes simples. Um cruzamento de teste envolve a reprodu&#xE7;&#xE3;o, ou cruzamento, do organismo em quest&#xE3;o com outro exibindo a contraparte recessiva da sua caracter&#xED;stica dominante.
 
 Em um cruzamento de teste para uma planta de ervilha com flores roxas, a planta &#xE9; cruzada com uma planta de ervilha que tem flores brancas (gen&#xF3;tipo pp). A cor das flores da progenia resultante revela se o progenitor com flores roxas &#xE9; homozig&#xF3;tico (PP) ou heterozig&#xF3;tico (Pp).
 
 Se a planta for homozig&#xF3;tica, toda a progenia herdar&#xE1; um dos seus alelos P dominantes e um dos alelos p recessivos do outro progenitor. Uma vez que alelos dominantes mascaram alelos recessivos, todos os descendentes ter&#xE3;o flores roxas, o tra&#xE7;o dominante.
 
 Se a planta for heterozig&#xF3;tica, no entanto, cerca de 50% da progenia herdar&#xE1; o seu alelo p recessivo, juntamente com outro alelo recessivo do outro prognitor. Portanto, cerca de metade dos descendentes deste cruzamento ter&#xE3;o flores brancas. Desta forma, os cruzamentos de teste podem revelar gen&#xF3;tipos parentais desconhecidos.

Cruzamento Teste

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

Biologia Molecular

Unit 2

Unidade 2

Analyzing Gene Expression and Function

Analisando a Expressão e a Função Gênica

KEY TERMS AND CONCEPTS

TERMOS-CHAVE E CONCEITOS

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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Reporter genes are protein-coding genes used to track gene activity in cells. They are often tagged to a gene of interest so scientists can see whether that gene is present or active. When the tagged genes are expressed together, reporter genes can produce visible signals such as fluorescence or luminescence. These signals help show the presence or absence of a gene of interest in an organism. They can also reveal the pattern of gene expression or the location of a DNA segment or protein...

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Synthetic biology combines engineering, molecular biology, cell biology, and systems biology to redesign living systems. Scientists use it to remodel organisms from nature or to build new synthetic organisms. These tools can support protein or enzyme production, bioremediation, the production of useful macromolecules, and the addition of helpful traits to crops. One well-known example is golden rice. This genetically modified rice plant makes grains rich in β-carotene, which is a precursor of...

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transgenic plants

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Transgenic plants are crops that have been changed with recombinant DNA technology, also called transgenesis. This method adds a foreign gene or removes a harmful one from an organism. The result is a genetically modified organism. The first transgenic plant was a tobacco plant made in 1983, and it was resistant to tobacco mosaic virus. Since then, transgenic plants have been developed for many uses in agriculture, horticulture, and ornamental plants. Some are designed to resist pests or...

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Gene Interaction Maps in Epistasis

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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 Biologia Molecular mostra os processos moleculares da célula através de vídeos de animação claros e concisos. Além disso, nos vídeos de Cientistas em ação, a aplicação desses conceitos é demonstrada por meio de experimentos reais em laboratórios modernos.

Test Cross in Genetic Inheritance

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