Haploid

Tryptase is at the present moment the main clinical marker for anaphylaxis and mastocytosis. There are two major human mast cells tryptases, a- and (3-tryptase, encoded by two genes located at chromosome 16. The haploid genotype for tryptase is (3a or (3(3.25% of individuals are a-tryptase-deficient a-tryptase shows a 90% amino acid sequence identity with (3-tryptase. 

The 3x10 base pairs of DNA in humans are organized into the haploid complement of 23 chromosomes. The exact sequence of these 3 billion nucleotides defines the uniqueness of each individual. 

The DNA in a eukaryotic genome can be divided into different sequence classes. These are unique-sequence, or nonrepetitive, DNA and repetitive-sequence DNA. In the haploid genome, unique-sequence DNA generally includes the single copy genes that code for proteins. The repetitive DNA in the haploid genome includes sequences that vary in copy number from two to as many as 10 copies per cell. 

Repetitive-sequence DNA can be broadly classified as moderately repetitive or as highly repetitive. The highly repetitive sequences consist of 5-500 base pair lengths repeated many times in tandem. These sequences are usually clustered in centromeres and telomeres of the chromosome and are present in about 1-10 milHon copies per haploid genome. These sequences are transcriptionally inactive and may play a strucmral role in the chromosome (see Chapter 40). 

The moderately repetitive sequences, which are defined as being present in numbers of less than 10 copies per haploid genome, are not clustered but are interspersed with unique sequences. In many cases, these long interspersed repeats are transcribed by RNA polymerase II and contain caps indistinguishable from those on mRNA. 

Fig. 2.4 The budding pattern in haploid and diploid Saccharomyces cerevisiae. The original cell which formed a bud is the mother (M). The daughter cell (D) is shown remaining attached as might be the case in i colonies growing on the surface of agar.

Fig. 2.6 The moqjhological events of sporulation in Saccharomyces cerevisiae. (a) starved cell V, vacuole LG, lipid granule ER, endoplasmic reticulum CW, cell wall M, mitochondrion S, spindle pole SM, spindle microtubules N, nucleus NO, nucleolus, (b) Synaptonemal complex (SX) and development of polycomplex body (PB) along with division of spindle pole body in (c). (d) First meiotic division which is completed in (e). (f) Prepararation for meiosis II. (g) Enlargement of prospore wall, culminating in enclosure of separate haploid nuclei (h). (i) Spore coat (SC) materials produced and deposited, giving rise to the distinct outer spore coat (OSC) seen in the completed spores of the mature ascus (j). Reproduced from the review by Dickinson (1988) with permission from Blackwell Science Ltd.

Wright R.M., Repine T. Repine J.E. (1993) Reversible pseudohyphal growth in haploid Saccharomyces cerevisiae is an aerobic process. CurrGenet, 23, 388-391. 

Genome Haploid sets of chromosomes with their associated genes. 

Ponzetto, C., and Wolgemuth, D. J. (1985). Haploid expression of a unique c-abl transcript in the mouse male germ line. Mol. Cell. Biol. 5 1791-1794. 

The amount of genomic DNA in a particular organism is roughly proportional to the complexity of the organism. Table shows the content of DNA in the genomes of several widely different organisms. The data are normalized to a haploid set of chro-mosomes, since some cells listed are haploid and others are diploid. The DNA content... 

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 ... 

Rapid sequencing and single nucleotide polymorphisms (SNPs) will play a major role in associating sequence variations with heritable clinical phenotypes of drug or xenobiotic response. SNPs occur approximately once every 300-3,000 base pairs if one compares the genomes of two unrelated individuals [13, 14]. Any two individuals thus differ by approximately 1-10 million base pairs, i.e., in < 1% of the approximately 3.2 billion base pairs of the haploid genome (23 chromosomes). 

Diploid The full set of paired chromosomes (one chromosome set from each parent). The diploid human genome has 46 chromosomes (see also haploid). 

Haploid A single set of chromosomes (in humans the 23 chromosomes from either father or mother or the single set of chromosomes in their reproductive cells) (see also diploid). 

Meiosis Two consecutive cell divisions in the diploid progenitors of sex cells that result in four rather than two daughter cells, each with a haploid set of chromosomes. 

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