Chromosomes disorders

Chromosomal Disorders Autosomal Trisomy 21 Trisomy 18 Trisomy 13 Translocations Deletions ... 

Human cells normally contain 23 pairs of chromosomes, for a total of 46 chromosomes in each cell. A change in the number of chromosomes leads to a chromosomal disorder. These changes can occur during the formation of reproductive cells (eggs and sperm) or in early fetal development. A gain or loss of chromosomes from the normal 46 is called aneuploidy. 

Chromosomal disorders can also be caused by changes in chromosome structure. These changes are caused by the breakage and reunion of chromosome segments when an egg or sperm cell is formed or in early fetal development. Pieces of DNA can be rearranged within one chromosome, or transferred between two or more chromosomes. The effects of structural changes depend on their size and location. Many different structural changes are possible some cause medical problems, while others may have no effect on a person s health. 

Although it is possible to inherit some types of chromosomal abnormalities, most chromosomal disorders (such as Down syndrome and Turner syndrome) are not passed from one generation to the next. 

Changes in chromosome structure can also cause chromosomal disorders. Some changes in chromosome structure can be inherited, while others occur as random accidents during the formation of reproductive cells or in early fetal development. Because the inheritance of these changes can be complex, people concerned about this type of chromosomal abnormality may want to talk with a genetics professional. 

A personal or family history of a genetic condition, birth defect, chromosomal disorder, or hereditary cancer. 

A woman who is pregnant or plans to become pregnant at or after age 35. (Some chromosomal disorders occur more frequently in children bom to older women.)... 

Down syndrome. A chromosome disorder characterized by a small, antheropos-teriorly flattened skull short, flat-bridge nose epicanthal fold short phalanges widened spaces between the first and second digits of hands and feet and moderate to severe mental retardation. 

The genetic effects that could be caused by radiation are too numerous to be considered individually. For nuclear accident risk assessment, genetic disorders have been grouped as (1) dominant and X-linked single-gene disorders, (2) chromosome disorders, and (3) multifactorial disorders. 

Sancken U, Bartels I. Biochemical screening for chromosomal disorders and neural tube defects (NTD) is adjustment of maternal alpha-fetoprotein (AFP) still appropriate in insulin-dependent diabetes mellitus (IDDM) Prenat Diagn 2001 21 383-6. 

Advanced maternal age is associated with higher risks for chromosomal disorders (e.g., Down s syndrome, trisomy 13), while advanced paternal age is associated with higher risks for new mutations (e.g., those producing achondroplasia or Marfan s syndrome). 

A newborn girl is found to have marked swelling of the dorsal areas of her feet along with a broad (webbed) neck, a broad chest, and a heart murmur that is due to coarctation of the aorta. Her physician suspects a chromosomal disorder and orders a karyotype. Which of the results pictured below is most likely ... 

Congenital adrenal hyperplasia Congestive heart failure Chromosome disorders Chromosome mosaicism Chromosome translocation Copper excess Cri-du-chat syndrome Crouzon s syndrome Cushing s syndrome Cyanide poisoning Cystic fibrosis Diabetes insipidus Diabetes mellitus Dinitrophenol poisoning Diphtheria... 

Most common of the chromosomal disorders Most common cause of inherited mental retardation... 

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