Genetic imbalance is to describe situation when the
genome of a cell or organism has more copies of some genes than other genes due to
chromosomal
A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are ...
rearrangements or
aneuploidy.
Changes in
gene dosage, the number of times a given gene is present in the
cell nucleus
The cell nucleus (pl. nuclei; from Latin or , meaning ''kernel'' or ''seed'') is a membrane-bound organelle found in eukaryotic cells. Eukaryotic cells usually have a single nucleus, but a few cell types, such as mammalian red blood cells, h ...
, can create a genetic imbalance.
Effects
This imbalance in gene dosage alters the amount of a particular
protein relative to all other proteins, and this alternation in the relative amounts of protein can have a variety of
phenotypic effects. These effects are depending on how the proteins function and how critical the maintenance of a precise ratio of proteins is to the
survival of the organism.
Diminishing the dosage of most genes produces no obvious change in
phenotype. For some genes the phenotypic consequences of a decrease in gene dosage are noticeable but not catastrophic. For example, ''Drosophila'' containing only one copy of the
wild type Notch gene has visible wing abnormalities but otherwise seems to function normally. For some rare genes, the normal
diploid
Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectively ...
level of
gene expression
Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product that enables it to produce end products, protein or non-coding RNA, and ultimately affect a phenotype, as the final effect. The ...
is essential to individual survival; fewer than two copies of such a gene results in
lethality. In
Drosophila, a single dose of the locus known as Triplolethal is in an otherwise diploid individual.
Although a single dose of any gene may not cause substantial harm to the individual, the genetic imbalance resulting from a single dose of many genes at the same time can be lethal. Humans, for example, cannot survive, even as
heterozygotes, with
deletion
Deletion or delete may refer to:
Computing
* File deletion, a way of removing a file from a computer's file system
* Code cleanup, a way of removing unnecessary variables, data structures, cookies, and temporary files in a programming language
* ...
s that remove more than about 3% of any part of their
haploid
Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectively ...
genome.
References
*
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Genetics