sex ratio

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ratio

 [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.
A/D ratio adult versus developmental toxicity ratio; the ratio between the toxic effects of a substance on adults (humans or animals, especially pregnant females) and such effects on developing embryos or fetuses.
A-G ratio (albumin-globulin ratio) the ratio of albumin to globulin in blood serum, plasma, cerebrospinal fluid, or urine.
arm ratio a figure expressing the relation of the length of the longer arm of a mitotic chromosome to that of the shorter arm.
benefit-risk ratio a determination of the potential of a research study for positive effects on patients compared to the risks of doing harm.
cardiothoracic ratio on a chest 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.
grid ratio a ratio comparing the height of lead lines in an x-ray grid to the distance between the lead strips.
inspiratory-expiratory ratio the ratio of the inspiratory time to the expiratory time during the breathing cycle. Normally, expiratory time will be longer than inspiratory time; if the inspiratory time is longer than the expiratory time, gas trapping may result.
lecithin/sphingomyelin ratio see lecithin-sphingomyelin ratio.
risk ratio relative risk.
sex ratio the proportion of one sex to the other; by tradition the number of males in a population to the number of females, usually stated as the number of males per 100 females.
signal-to-noise ratio the ratio between the amplitude of a signal being measured and that of the noise.
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.
zeta sedimentation ratio (ZSR) a measurement comparable to the erythrocyte sedimentation rate, except that it is unaffected by anemia. The packed-cell volume (zetacrit) of a blood specimens is calculated by centrifuging the specimen in a Zetafuge, a specially designed instrument that produces controlled cycles of compaction and dispersion and allows rouleaux to form and sediment rapidly. The zetacrit divided into the true hematocrit gives the zeta sedimentation ratio.

sex ra·ti·o

1. the ratio of male to female progeny at some specified stage of the life cycle, notably at conception (primary), at birth (secondary), or at any stage between birth and death (tertiary);
2. the ratio of the numbers of males to females affected by a particular disease or trait.

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.
The ratio of males to females in a population, which in humans—without ‘culling'—hovers at 105–107:100

sex ra·ti·o

(seks rā'shē-ō)
1. The ratio of male to female progeny at some specified stage of the life cycle, notably at conception (primary), at birth (secondary), or at any stage between birth and death (tertiary).
2. The ratio of the numbers of males to females affected by a particular disease or trait.
Sex ratioclick for a larger image
Fig. 284 Sex ratio . The ratio of male to female progeny in humans.

sex ratio

the number of males in a group divided by the number of females, giving a value which is usually about 1.0. The ratio is controlled by the SEGREGATION of SEX CHROMOSOMES in the HETEROGAMETIC SEX during MEIOSIS (see SEX DETERMINATION). For example, in humans the situation is normally as shown in Fig. 284. In fact, in humans there are often slightly more males born than females (105:100 is typical) due either to preferential fertilization of eggs by Y-carrying sperm causing an unequal primary ratio or to preferential survival of males during GESTATION. Whatever the reason, the sex ratio at birth (the secondary ratio) becomes altered to about 1:1 at sexual maturity in natural circumstances, due to the slightly higher mortality of male children.

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.

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.

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.

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
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.
References in periodicals archive ?
Patna At a time when the declining gender ratio and the environmental imbalances have been the cause of global concern, a village in the eastern Indian state of Bihar has emerged as a role model for others by addressing the twin issues through a method not unheard of till date.
So the relationship between the gender ratio and violence turns out to be paradoxical.
However WFP monitors closely the gender ratio in its beneficiary caseload to ensure equitable access
The gender ratio during the study period was 4 females: 1 male, which is different from the reference value according to Barragan (1977b).
As a result, the gender ratio in the village is now tilted in favour of girls," says she.
A girls' advocacy group, SPARK Movement, released a report noting the gender ratio in four years worth of data on Google doodles.
The census gender ratio in the city -- 868 women per 1,000 men -- is anyway poor and the electoral gender ratio is even lower.
Yet year after year the gender ratio in India becomes more and more skewed in favour of the male.
Mumbai The Konkan district of Ratnagiri has the widest gender ratio in Maharashtra at 1,123 females per 1,000 males followed by Sindhudurg at 1,037.
RANTHAMBHORE National Park is facing a serious imbalance in the tigers' gender ratio that has come down to 1: 1.
The steeper the gender ratio (also known as the operational sex ratio), the sharper the decline in lifespan.
The gender ratio of graduates is fairly close at 52 percent female and 48 percent male.