Sex-linked inheritance Health Dictionary

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Sex-linked Inheritance: From 2 Different Sources

The passing on to the next generation of a trait or disorder determined by the sex chromosomes, or by the genes carried on them.

Disorders caused by an abnormal number of sex chromosomes include Turner’s syndrome and Klinefelter’s syndrome.

Most other sex-linked traits or disorders are caused by recessive genes on the X chromosome (see genetic disorders).

Health Source: BMA Medical Dictionary
Author: The British Medical Association
The way in which a characteristic or an illness determined by the SEX CHROMOSOMES in an individual’s cells is passed on to the succeeding generation. Men have one X and one Y sex chromosome and women have two X chromosomes. Disorders that result from an abnormal number of sex chromosomes include KLINEFELTER’S SYNDROME, which affects only men, and TURNER’S SYNDROME, which affects mainly women. Recessive GENES on the X chromosome cause most other sex-linked characteristics; in women these may well be masked because one of their two X chromosomes carries a normal (dominant) gene. In men, who have just one X chromosome, no such masking occurs – so more men than women are affected by X-linked characteristics or diseases. (See also HEREDITY.)
Health Source: Medical Dictionary
Author: Health Dictionary

Inheritance

The transfer of characteristics, traits and disorders from parents to children by means of

GENES carried in the CHROMOSOMES of the germ cells. (See GERM CELL; GENETIC CODE; GENETIC DISORDERS.)... inheritance

Enzyme-linked Immunosorbent Assay (elisa)

This is a sensitive method for measuring the quantity of a substance. An antibody to the substance is prepared along with an ENZYME which binds to the antibody and which can be accurately measured using colour changes that occur as a result of the chemical reaction.... enzyme-linked immunosorbent assay (elisa)

Pituitary-linked Disorders

ACROMEGALY or gigantism is the result of the overactivity of, or tumour formation of cells in, the adenohypophysis which produces GROWTH HORMONE (see also PITUITARY GLAND). If this overactivity occurs after growth has ceased, acromegaly arises, in which there is gross overgrowth of the ears, nose, jaws, and hands and feet. DWARFISM may be due to lack of growth hormone.

DIABETES INSIPIDUS, a condition characterised by the passing of a large volume of URINE every day, is due to lack of the antidiuretic hormone (see VASOPRESSIN). Enhanced production of the ADRENOCORTICOTROPHIC HORMONE (ACTH) leads to CUSHING’S SYNDROME. Excessive production of PROLACTIN by micro or macro adenomas (benign tumours) leads to hyperprolactinaemia and consequent AMENORRHOEA and GALACTORRHOEA. Some adenomas do not produce any hormone but cause effects by damaging the pituitary cells and inhibiting their hormone production.

The most sensitive cells to extrinsic pressure are the gonadotrophin-producing cells and the growth-hormone producing cells, so that if the tumour occurs in childhood, growth hormone will be suppressed and growth will slow. Gonadotrophin hormone suppression will prevent the development of puberty and, if the tumour occurs after puberty, will result in amenorrhoea in the female and lack of LIBIDO in both sexes. The thyroid-stimulating hormone cells are the next to suffer and the pressure effects on these cells will result in hypothyroidism (see under THYROID GLAND, DISEASES OF).

Fortunately the ACTH-producing cells are the most resistant to extrinsic pressure and this is teleologically sound as ACTH is the one pituitary hormone that is essential to life. However, these cells can suffer damage from intracellular tumours, and adrenocortical insu?ciency is not uncommon.

Information about these disorders may be obtained from the Pituitary Foundation.... pituitary-linked disorders

X-linked Disorders

Sex-linked genetic disorders in which the abnormal gene or genes (the causative factors) are located on the X chromosome. Almost all affected people are males. Haemophilia, fragile X syndrome. and colour vision deficiency are examples.... x-linked disorders

Cytoplasmic Inheritance

the inheritance of characters controlled by genes present in the cell cytoplasm rather than by genes on the chromosomes in the cell nucleus. An example of cytoplasmic inheritance is that controlled by mitochondrial genes (see mitochondrion).... cytoplasmic inheritance

Enzyme-linked Immunosorbent Assay

(ELISA) a sensitive technique for measuring the amount of a substance. An antibody that will bind to the substance is produced; the amount of an easily measured enzyme that then binds to the antibody complex enables accurate measurement.... enzyme-linked immunosorbent assay

Sex-linked

adj. describing genes (or the characteristics controlled by them) that are carried on the sex chromosomes, usually the *X chromosome. The genes for certain disorders, such as *haemophilia, are carried on the X chromosome; these genes and disorders are described as X-linked. Since most of these sex-linked genes are *recessive, men are more likely to have the diseases since they have only one X chromosome; women can carry the genes but their harmful effects are usually masked by the dominant (normal) alleles on their second X chromosome.... sex-linked

X-linked Disease

see sex-linked.... x-linked disease

X-linked Lymphoproliferative Syndrome

(XLP syndrome, Duncan’s disease) a hereditary disorder of the immune system caused by a defective *sex-linked gene carried on an *X chromosome. There is uncontrolled proliferation of B-*lymphocytes in response to infection by the Epstein-Barr virus, which can lead to fulminating hepatitis or lymphoma. This condition is due to a defect in a gene, SAP, which encodes a signalling molecule found in the cytoplasm of cells.... x-linked lymphoproliferative syndrome

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