Yeasts diploid

Bertsche U. 1978. The response of diploid yeast to radiations at different LET I. Potentially lethal and lethal damage to reproductive capacity. Radiat Res 76 349-367. 

Figure 5.2. High-throughput mating assay for two-hybrid protein interaction screening. Yeast strains containing individual bait and prey clones are combined in a well and allowed to mate. Diploids are then selected and scored for a protein-protein interaction using the selection provided by the transcriptional reporter gene.

Kharab P, Singh I. 1985. Genotoxic effects of potassium dichromate, sodium arsenite, cobalt chloride and lead nitrate in diploid yeast. MutRes 155 117-120. 

Haploid cells have only a single copy of each chromosome. This occurs normally in the mature germ cell. Diploid cells, in contrast have two copies of each chromosome most normal somatic cells are diploid. The fact that yeast cells are haploid renders genetic analysis much easier because one has taken sex out of the equation - the question remains whether it is as much fun ... 

Murthy MS Induction of gene conversion in diploid yeast by chemicals Correlation with mutagenic action and its relevance in geno-toxicity screening. Mutat Res 1979 64 1-17. 

Marrot, L. and Agapakis-Causse, C. (2000) Differences in the photogenotoxic potential of two fluoroquinolones as shown in diploid yeast strain (Saccharomyces cerevisae) and supercoiled plasmid DNA. Mutation Research, 468, 1-9. 

Yeast cells can exist as haploids of opposite mating types (either a or a). When an a and an a cell are allowed to mate, they form a diploid cell (a/a). To study interactions between two proteins, cDNA sequences of a protein of interest (PT1) are expressed as a fusion protein, linked to a DNA-binding domain (DBD) of a yeast gene-transcript activator in a haploid cell (e.g., a). cDNA sequences corresponding to another test protein (PT2) are linked to the Continued on next page)... 

Figure 16.1. Schematic representation of the yeast two-hybrid system for evaluation of protein-protein interactions. Haploid yeast of a and a cells can mate to form (a/a) diploid cells. (A) If two test proteins, PT1 and PT2—expressed in (a/a) diploid cells as fusion proteins of DNA binding domains (DAB) and activation domains (AD) of yeast gene-transcript activator proteins—bind to each other, the binding interaction allows the diploid cells to grow in histidine selection media. Histidine selection media is permissive for diploid cells that express the HISS reporter gene only if PT1 and PT2 interact. (B) If PT1 and PT2 do not interact, no HISS gene product is expressed and the hybrid cell cannot grow in histidine media.

Eukaryotes A yeast cell, one of the simplest eukaryotes, has 2.6 times more DNA in its genome than an E. coli cell (Table 24-2). Cells of Drosophila, the fruit fly used in classical genetic studies, contain more than 35 times as much DNA as E. coli cells, and human cells have almost 700 times as much. The cells of many plants and amphibians contain even more. The genetic material of eukaryotic cells is apportioned into chromosomes, the diploid (2n) number depending on the species (Table 24-2). A human somatic cell, for example, has 46 chro-... 

Note This information is constantly being refined, For the most current information, consult the websites for the individual genome projects, The diploid chromosome number is given for all eukaryotes except yeast,... 

The amount of nucleic acid in tissues varies from 0.1% in yeast and 0.5-1% in muscle and in bacteria to 15-40% in thymus gland and sperm cells. In these latter materials of high nucleic acid content it is clear that multiplication of % N by 6.25 is not a valid measure of protein content. For diploid cells of the body the DNA content per cell is nearly constant. 

Phenotypes of Haploid and Diploid Yeast with Regulatory Gene Mutations... 

Yeast has two haploid cell mating types MATa (or simply a) and MATa (or a) on contact, haploid cells of opposite mating types fuse to form a single diploid ala) cell. Diploid cells can grow and divide indefinitely as diploid cells, or they can sporulate, a process in which they undergo mei-osis and give rise to two a and two a cells for each diploid cell. The haploid mating type is determined by specific sequences at the MAT locus (fig. 31.5). These sequences are found at the HMLa or HMRa loci, where they are usually not expressed. When the sequences stored at the HMLa locus are transposed to MAT, they express similarly when sequences are transposed from HMRa to MAT, they express. 

Regulation of meiosis in yeast. Haploid cells are not able to initiate meiosis because they express RME1, which is a negative regulator of meiosis. Diploid cells are able to initiate meiosis because they make a complex of al and a 1 that inhibits the synthesis of the RME 1 product. 

Most higher animals and plants are diploid. Some of the most important experimental species, such as the bacterium Escherichia coli, are haploid. Still others, such as yeasts, may be either haploid or diploid. 

Eukaryotes Can do post-translational modifications can accept large genes. Do not have plasmids (except yeast) often diploid so two copies of genes may need to be inserted control of expression not well understood. 

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