Nullisomy

Nullisomy

 

a type of genome mutation in which a pair of chromosomes that are normally present in the genome is missing. Organisms that exhibit nullisomy are called nullisomes. Nullisomy, especially in higher animals, usually results in death. Viable nullisomes can be found among polyploid plants; these nullisomes are used for nullisomic analysis and for establishing new, commercially valuable strains. Nullisomic analysis is used to determine genetic linkage groups and to study the traits that are controlled by these groups. The method is also applied to tissue-culture studies of human nullisomic cells.

References in periodicals archive ?
The remaining 4.05% were aneuploidy; more specifically, 0.18% were disomy 18, 2.12% were sex disomy, 1.65% were sex nullisomy, and 0.18% diploid.
The dependent variables from the sperm ACM-FISH assay include duplications of lp36.3, deletions of lp36.3, duplications of the lcen region, deletions of the lcen region, breaks in 1q12, breaks between 1q12 and lcen, and numerical aberrations including diploidy/disomy of chromosome 1 and chromosome 1 nullisomy. Because only one chromosome is examined in this assay, diploidy cannot be distinguished from disomy of chromosome 1.
summarize total duplications (lp36.3 + lcen), deletions (lp36.3 + lcen), breaks (breaks in 1q 12 + breaks between 1q12 and lcen), structural aberrations (all duplications, deletions, and breaks), and numerical aberrations (diploidy/disomy + nullisomy).
4B and monosomy for chromosome 18 in 12 blastomeres out of 48 blastomeres of the embryo i.e., double mosaic monosomy), one with ch.1 nullisomy 1/33 blastomeres (Fig.5) and one was trisomy for sex chromosome (XXY; triplod status was not ruled out by chromosome 1 FISH).
1 monosomy 1/48 1,18,18 (1)/1,1,18 (12)/ blastomeres (1,18,18) & ch.18 1,1,18,18 (5) monosomy 12/48 blastomeres (1,1,18) Other with ch.l nullisomy 1/33 0,0,18,18 (1)/1,1,18,18 (32) blastomeres (0,0,18,18) Chromosome XY FISH 14 XY 10 (2-8 cells stage embrys) XX 03 (2-8 cells stage embrys) XXY (triploidy state not ruled 01 (5 cells stage embryo) out by ch.
In the absence of the wheat Ph1 pairing gene, either through nullisomy for 5B or the presence of the ph1b gene, increased meiotic associations have been observed between wheat and rye chromosomes but still at a low level (Upadhya and Swaminathan, 1963; Lacadena, 1967; Dhaliwal et al., 1977; Hutchinson et al., 1983; Schnaider and Priilinn, 1984; Jouve and Giorgi, 1986; Wu et al., 1989: Naranjo and Fernfindez-Rueda, 1991; Cuadrado et al., 1997).
Several mechanisms of aneuploid decrease or increase are well documented in angiosperm evolution, including descending and ascending dysploidy, nullisomy, and tetrasomy (Stebbins 1950; Darlington 1973; White 1978; Stace 1980; Grant 1981).
Thirty somatic chromosomes originate through tetrasomy, while a tetraploid with 56 somatic chromosomes is reduced by nullisomy to 54 somatic chromosomes.
The following categories of sperm aneuploidy were included as dependent variables: disomy X (sperm FISH genotype X-X-21); disomy Y (Y-Y-21); disomy XY (X-Y-21); disomy 21 (X-21-21 or Y-21-21); overall hyperhaploidy involving chromosomes X, Y, and 21 (sum of XY, disomy X, disomy Y, and disomy 21); sex nullisomy (_21); 21 nullisomy (X_ or Y_); overall hypohaploidy involving chromosomes X, Y, and 21 (sum of sex nullisomy and 21 nullisomy); and diploidy.
This is because some anomalies, such as disomy or nullisomy 21, are rare events that occur only in a subgroup.
However, in a critical cross, all [F.sub.3] families should be resistant (except for rare susceptible plants arising from nullisomy).
A moderately increased prevalence of chromosomes X, Y, and 18 sperm aneuploidies was also observed in these workers but nullisomy was not scored (15).