Information about Chromosomal Inversion
)
A clay model showing why heterozygous inversion loops are visible in polytene chromosome preparations
)
An inversion loop in the A arm of a chromosome from an Axarus species midge
An inversion is a chromosome rearrangement in which a segment of a chromosome is reversed end to end. An inversion occurs when a single chromosome undergoes breakage and rearrangement within itself. Inversions are of two types: paracentric and pericentric. Paracentric inversions do not include the centromere and both breaks occur in one arm of the chromosome. Pericentric inversions include the centromere and there is a break point in each arm. Special cytogenetics techniques are often needed to detect inversions. In the "giant" polytene chromosomes found in some organisms, inversions can be easily visualized when they are heterozygous. This is a very useful characteristic of polytene chromosomes that was first noted by Theophilus Shickel Painter in 1933.
Inversions usually do not cause any abnormalities in carriers as long as the rearrangement is balanced with no extra or missing genetic information. However, there is an increased chance for the production of unbalanced chromosome rearrangements in the offspring of carriers. Families that may be carriers of inversions may be offered genetic counseling and genetic testing.
The most common inversion seen in humans is on chromosome 9, at inv(9)(p11q12). This inversion is generally considered to have no deleterious or harmful effects, but there is some evidence it leads to an increased risk for miscarriage for about 30% of affected couples.
References
- Painter, TS (1933). "A new method for the study of chromosome rearrangements and the plotting of chromosome maps.". Science 78: 585-586. l
See also
External links
Evolution of chromosomes
|
|---|
| Basic topics: Chromosome | Karyotype | Ploidy | Meiosis |
| Classification: Autosome | Sex chromosome |
| Evolution: Chromosomal inversion | Chromosomal translocation | Polyploidy |
Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division.]] A chromosome is a single large macromolecule of DNA, and constitutes a physically organized form of DNA in a cell.
..... Click the link for more information.
..... Click the link for more information.
centromere is a region of chromosomes with a special sequence and structure. The centromere plays a role in cellular division and the control of gene expression.
..... Click the link for more information.
Function
..... Click the link for more information.
Cytogenetics is the study of the structure of chromosome material. It includes routine analysis of G-Banded chromosomes, other cytogenetic banding techniques, as well as molecular cytogenetics such as fluorescent in situ hybridization (FISH) and comparative genomic hybridization
..... Click the link for more information.
..... Click the link for more information.
polytene chromosome. Polytene chromosomes form when multiple rounds of replication produce chromatids that remain synapsed together in a haploid number of chromosomes. They have characteristic light and dark banding patterns which can be used to identify chromosomal rearragements
..... Click the link for more information.
..... Click the link for more information.
Zygosity refers to the genetic condition of a zygote. In genetics, zygosity describes the similarity or dissimilarity of DNA between homologous chromosomes at a specific allelic position or gene.
Every gene in a diploid organism has two alleles at the gene's locus.
..... Click the link for more information.
Every gene in a diploid organism has two alleles at the gene's locus.
..... Click the link for more information.
polytene chromosome. Polytene chromosomes form when multiple rounds of replication produce chromatids that remain synapsed together in a haploid number of chromosomes. They have characteristic light and dark banding patterns which can be used to identify chromosomal rearragements
..... Click the link for more information.
..... Click the link for more information.
Theophilus Shickel Painter (August 22, 1889 – October 5, 1969) was an American zoologist known for his work in identifying genes in fruit flies (Drosophila). He did so by applying the incredible detail that had just been discovered to be visible in the giant polytene
..... Click the link for more information.
..... Click the link for more information.
Genetic counseling is the process by which patients or relatives, at risk of an inherited disorder, are advised of the consequences and nature of the disorder, the probability of developing or transmitting it, and the options open to them in management and family planning in order
..... Click the link for more information.
..... Click the link for more information.
Genetic testing allows the genetic diagnosis of vulnerabilities to inherited diseases, and can also be used to determine a person's ancestry. Every person carries two copies of every gene, one inherited from their mother, one inherited from their father.
..... Click the link for more information.
..... Click the link for more information.
chromosome abnormality reflects an abnormality of chromosome number or structure. Chromosome abnormalities usually occur when there is an error in cell division following meiosis or mitosis. There are many types of chromosome abnormalities.
..... Click the link for more information.
..... Click the link for more information.
Figure 1: A representation of a condensed eukaryotic chromosome, as seen during cell division.]] A chromosome is a single large macromolecule of DNA, and constitutes a physically organized form of DNA in a cell.
..... Click the link for more information.
..... Click the link for more information.
karyotype is the observed characteristics (number, type, shape etc) of the chromosomes of an individual or species.
In normal diploid organisms, autosomal chromosomes are present in two identical copies, although polyploid cells have multiple copies of chromosomes and
..... Click the link for more information.
In normal diploid organisms, autosomal chromosomes are present in two identical copies, although polyploid cells have multiple copies of chromosomes and
..... Click the link for more information.
Ploidy is the number of homologous sets of chromosomes in a biological cell. The ploidy of cells can vary within an organism. In humans, most cells are diploid (containing one set of chromosomes from each parent), but sex cells (sperm and egg) are haploid.
..... Click the link for more information.
..... Click the link for more information.
meiosis (IPA: /maɪˈəʊsɪs/) is the process by which one diploid eukaryotic cell divides to generate four haploid cells often called gametes.
..... Click the link for more information.
..... Click the link for more information.
An autosome is a non-sex chromosome. It is an ordinarily pairedIn the case of higher ploidy levels than the usual diploid, there will be the same number of an autosome as the ploidy level itself. For example, in a pentaploid, there will be five copies of each autosome.
..... Click the link for more information.
..... Click the link for more information.
A sex-determination system is a biological system that determines the development of sexual characteristics in an organism. Most sexual organisms have two sexes. In many cases, sex determination is genetic: males and females have different alleles or even different genes that
..... Click the link for more information.
..... Click the link for more information.
chromosome translocation is a chromosome abnormality caused by rearrangement of parts between nonhomologous chromosomes. It is detected on cytogenetics or a karyotype of affected cells.
..... Click the link for more information.
..... Click the link for more information.
Polyploidy is the condition of some biological cells and organisms manifested by the presence of more than two homologous sets of chromosomes. Polyploid types are termed according to the number of chromosome sets in the nucleus: triploid (three sets; 3x),
..... Click the link for more information.
..... Click the link for more information.
This article is copied from an article on Wikipedia.org - the free encyclopedia created and edited by online user community. The text was not checked or edited by anyone on our staff. Although the vast majority of the wikipedia encyclopedia articles provide accurate and timely information please do not assume the accuracy of any particular article. This article is distributed under the terms of GNU Free Documentation License.
Herod_Archelaus
