Chromosome.
Publié le 11/05/2013
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chromosome breaks off and attaches to another chromosome.
A translocation involving chromosomes 9 and 22 is linked to a type of leukemia called chronic myelogenicleukemia.
On the sex chromosomes, problems arise in men when an abnormal gene is present on the X chromosome.
With no healthy gene found on the Y chromosometo override the abnormal gene, disease may result.
For example, men who inherit a mutated gene that causes hemophilia from their mother on the X chromosome willdevelop this bleeding disorder since they are missing a normal version of the gene on their Y chromosome.
Scientists called cytogeneticists look at a person’s chromosomes in the laboratory to determine whether the individual has the usual number of chromosomes andwhether these chromosomes have missing or extra segments.
To examine chromosomes, cytogeneticists grow samples of a person’s blood cells in the laboratory andexpose the cells to a chemical called colchicine, which disrupts the spindle apparatus that is normally present in dividing cells.
This disruption immobilizes thechromosomes during cell division, when they are most condensed and visible.
Chromosomes are then stained with various dyes, which produce a pattern of verticalbands.
Cytogeneticists take photographs of the banded chromosomes through a microscope to create images called karyotypes, in which the members of eachchromosome pair are arranged next to each other for easy comparison.
The analysis of karyotypes reveals whether a person has extra or missing chromosomes, as wellas whether large segments of chromosomes are absent, rearranged, or duplicated.
Experiments involving artificial chromosomes—chromosomes that are synthesized in the laboratory—are providing new insights into the structure and function ofchromosomes.
The first artificial chromosomes, produced in the 1980s, were chromosomes of yeast cells.
The first artificial human chromosomes were created in 1997.
Researchers have successfully identified all the genes located on chromosomes 5, 16, 19, 21, and 22.
This research has revealed a number of disease-causing genesassociated with these chromosomes.
For instance, genes found on chromosome 5 have been linked to colorectal cancer, basal cell carcinoma (a form of skin cancer), and a type of dwarfism.
Chromosome 16 contains genes implicated in adult polycystic renal disease, which affects 5 million people worldwide.
Identifying disease-causing genes and their chromosome locations will help researchers devise new diagnostic tools to determine a person’s risk for disease as well as new therapies toreplace or repair faulty genes.
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Liens utiles
- chromosome.
- chromosome 1 PRÉSENTATION chromosome, structure cellulaire microscopique représentant le support physique des gènes et de l'information génétique, toujours constituée d'ADN, et souvent de protéines.
- cartographie des g?nes, ensemble des ?tudes g?n?tiques ou mol?culaires qui ont pour but de positionner un g?ne donn? sur un chromosome particulier.
- Vocabulaire: CHROMOSOME, substantif masculin.
- Vocabulaire: chromosome CHROMOSOME, substantif masculin.