sex ratio (redirected from Unbalanced sex ratio)

ratio /ra·tio/ (ra´she-o) [L.] an expression of the quantity of one substance or entity in relation to that of another; the relationship between two quantities expressed as the quotient of one divided by the other.

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A-G ratio , albumin-globulin ratio the ratio of albumin to globulin in blood serum, plasma, or urine in various renal diseases.

cardiothoracic ratio  on a radiograph, the ratio of the transverse diameter of the heart to the internal diameter of the chest at its widest point just above the dome of the diaphragm.

lecithin/sphingomyelin ratio , L/S ratio the ratio of lecithin to sphingomyelin concentration in the amniotic fluid, used to predict the degree of pulmonary maturity of the fetus and thus the risk of respiratory distress syndrome (RDS) if the fetus is delivered prematurely.

sex ratio  the proportion of one sex to another, traditionally the number of males in a population per number of females.

ventilation-perfusion ratio  the ratio of oxygen received in the pulmonary alveoli to the flow of blood through the alveolar capillaries.

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sex ratio

n.

1. The proportion of males to females in a given population, usually expressed as the number of males per 100 females at a specific stage in life, especially at conception, birth, and a given stage between birth and death.

2. The ratio of the numbers of males to females affected by a particular disease or trait.

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sex ratio,

the proportion of male-to-female progeny, a relationship that varies with the stage of life. The distribution at birth is usually 106 boys to 100 girls, but the ratio shifts in adulthood, so that, because men have a lower life expectancy, the proportion of females is greater. The ratio may also vary with the effects of a particular disease or trait.

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ratio

[L.] an expression of the quantity of one substance or entity in relation to that of another; the relationship between two quantities expressed as the quotient of one divided by the other. It differs from a proportion in that the numerator is not included in the denominator. Thus x/(x + y) is a proportion, x:y is a ratio.

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A-G ratio

albumin-globulin ratio.

area-incidence ratio

the number of new cases of a specific disease in a population during a specified time period, divided by the geographic area size in which the observations are made, multiplied by the time elapsed, e.g. cases per hectare per month.

arm ratio

a figure expressing the relation of the length of the longer arm of a mitotic chromosome to that of the shorter arm.

A/S ratio

the diameter of the ascending aorta divided by the diameter of the aorta at the sinus of Valsalva; less than 1 in a normal dog. In subaortic stenosis it becomes greater than 1.

cardiothoracic ratio

the ratio of the transverse diameter of the heart to the internal diameter of the chest at its widest point just anterior to the dome of the diaphragm.

cross ratio

see odds ratio.

fetal death ratio

the number of fetal deaths divided by the number of live births.

gain ratio

individual animal's gain/average gain in group × 100.

lecithin-sphingomyelin ratio

the ratio of lecithin to sphingomyelin in amniotic fluid. See also lecithin, sphingomyelin.

odds ratio

see odds ratio.

rates ratio

the ratio between two rates. See odds ratio and relative risk ratio (below).

relative risk ratio

the ratio between the rate (of mortality or some such parameter) in one group of animals and the rate in another group, used as a standard and the comparison expressed as a ratio. See also relative risk.

sex ratio

the number of males in a population per number of females, usually stated as the number of males per 100 females.

S/P ratio

secondary-to-primary ratio. An indicator of fleece type in sheep, the greater the ratio the finer the fleece. Coarse-wool sheep have ratios of 3:1 to 4:1; merinos have a ratio of 20:1.

stillbirth ratio

the ratio of stillbirths to total births in the population.

urea excretion ratio

the ratio of the amount of urea in the urine excreted in one hour to the amount in 100 ml of blood. The normal ratio is 50.

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sex

1. the fundamental distinction, found in most species of animals and plants, based on the type of gametes produced by the individual or the category to which the individual fits on the basis of that criterion. Ova, or macrogametes, are produced by the female, and spermatozoa, or microgametes, are produced by the male. The union of these distinctive germ cells results in the production of a new individual in sexual reproduction.

2. to determine the sex of an animal.

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sex cell

see germ cell, gamete.

sex chromatin

the persistent mass of chromatin situated at the periphery of the nucleus in cells of normal females; it is the material of the inactivated sex chromosome. Called also Barr body.

chromosomal sex

sex as determined by the presence of the XX (female) or the XY (male) genotype in somatic cells, without regard to phenotypic manifestations. Called also genetic sex.

sex chromosomes

see sex chromosomes.

sex determination

1. the change in the fetus to a male or female configuration; the process by which the sex of an organism is fixed, associated, in animals, with the presence or absence of the Y chromosome.

2. diagnosis of the sex of the fetus before birth performed by examination of fetal fluids obtained by amniocentesis.

sex determining region of Y

a single gene responsible for determining the sex of an animal.

sex drive

see libido.

endocrinological sex

the phenotypic manifestations of sex determined by endocrine influences, such as mammary development, etc.

genetic sex

chromosomal sex.

sex glands

in the male includes the prostate, seminal vesicles, ampullae and bulbourethral glands; in the female includes ovaries.

gonadal sex

the sex as determined on the basis of the gonadal tissue present (ovarian or testicular).

sex hormones

glandular secretions involved in the regulation of sexual functions. The principal sex hormone in the male is testosterone, produced by the testes. In the female the principal sex hormones are the estrogens and progesterone, produced by the ovaries.

These hormones influence the secondary sex characters, such as the shape and contour of the body and head, mammary development and the pitch of the voice. The male hormones stimulate production of spermatozoa, and the female hormones control ovulation, pregnancy and the estral cycle.

sex-linkage

includes X-linked (much the most common) and Y-linked loci.

sex-linked inheritance

see sex-linkage (above).

morphological sex

sex determined on the basis of the morphology of the external genitals.

neutrophil sex lobe

see drumstick lobe.

nuclear sex

the sex as determined on the basis of the presence or absence of sex chromatin in somatic cells, its presence normally indicating the XX (female) genotype, and its absence the XY (male) genotype.

sex parity

see sex ratio (below).

sex pheromone

see pheromone.

sex ratio

proportion of female to male births.

sex reversal

the sexual condition of animals in which gonadal sex and chromosomal sex are dissimilar.

sex steroids

steroidal compounds acting as hormones in reproductive processes; the principal ones are estrogen, progesterone, testosterone.