Tetrad (genetics)

Tetrad (genetics)

The tetrad is the four spores of a yeast or Chlamydomonas, that separate after mating. If the two parents have a mutation in two different genes, the tetrad can segregate as the parental ditype (PD), the non-parental ditype (NPD) or as the tetratype (TT).

Saccharomyces cerevisiae tetrad

Contents

Parental ditype

A tetrad type containing two different genotypes, both of which are parental. A spore arrangement in Ascomycetes that contains only the two non-recombinant-type ascospores.

Non-parental ditype

A non-parental ditype (NPD) is a spore arrangement in that contains only the two recombinant-type ascospores (assuming two segregating loci). A tetrad type containing two different genotypes, both of which are recombinant.

Tetratype

A Tetratype is a tetrad containing four different genotypes, two parental and two recombinant. A spore arrangement in Ascomycetes that consists of two parental and two recombinant spores indicates a single crossover between two linked loci.

Linkage analysis

The ratio between the different types arising after the sporulation is a measure of the linkage between the two genes.

Tetrad Dissection

Tetrad Dissection has become a powerful tool of yeast geneticists, and is used in conjunction with the many established procedures utilizing the versatility of yeasts as model organisms. Use of modern microscopy and micromanipulation techniques allows the four haploid spores of a yeast tetrad to be separated and germinated individually to form isolated spore colonies.

Uses

Tetrad analysis can be used to confirm whether a phenotype is caused by a specific mutation, construction of strains, and for investigating gene interaction.

General Procedure

Crosses are performed between haploid MATa and MATα mating strains, then the resulting diploids are transferred to sporulation media to form a tetrad containing four haploid spores. Tetrads can then be prepared with Zymolyase, or another enzyme, to digest the wall of the ascus. The spores are then separated with a micromanipulator needle and deposited in separate positions on a petri dish.

Tools

Traditionally, tetrad dissection has a reputation as "dark art" [1]. However, instruments have since been developed specifically for tetrad dissection; the most advanced allow easy and semi-automated separation of tetrads[1] . Most micromanipulators use a fiberglass needle to which the spores adhere due to the formation of a water meniscus between the agar and the needle.

See also

External links

References

  1. ^ Yeast Protocols: Methods in Cell and Molecular Biology, Ivor Howell Evan, Published by Humana Press, 1996, ISBN 0896033198, 9780896033191

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Look at other dictionaries:

  • tetrad — tetrad. См. тетрада. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • tetrad analysis — tetrad analysis. См. тетрадный анализ. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • tetrad segregation type — tetrad segregation type. См. сегрегация по тетрадному типу. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • Tetrad — may refer to:* Tetrad (chromosomal formation), a chromosomal formation in meiosis * Tetrad (general relativity), a mathematical frame of reference in general relativity * Tetrad (genetics), the four spores of a yeast * Tetrad (Greek philosophy),… …   Wikipedia

  • tetrad — [te′trad΄] n. [Gr tetras (gen. tetrados), four: see TETRA ] 1. a group or set of four 2. Bot. a group of four cells formed by division within a spore mother cell during meiosis 3. Chem. an atom, radical, or element that is tetravalent 4. Genetics …   English World dictionary

  • half-tetrad — half tetrad. См. полутетрада. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • ordered tetrad — ordered tetrad. См. линейная тетрада. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • pollen tetrad — pollen tetrad. См. пыльцевая тетрада. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • tetrad — 1. A collection of four things having something in common such as a deformity with four features, e.g., Fallot tetralogy. SYN: tetralogy. 2. In chemistry, a quadrivalent element. 3. In heredity, a bivalent ch …   Medical dictionary

  • tetrad — n. 1) (in genetics) the four cells resulting from meiosis after the second telophase. 2) the four chromatids of a pair of homologous chromosomes (see bivalent) in the first stage of meiosis …   The new mediacal dictionary

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