sex ratio

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Related to Birth ratio: Total fertility rate

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.
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.
References in periodicals archive ?
Third, bias might have been introduced using 1971 triplet and higher-order multiple birth ratios for direct age adjustment, which were based on a 50% sample of birth certificate data compared with 100% of data for 1985-1997.
Does either "theory" explain the out-of-wedlock birth ratio among African Americans?
"While the overall United Kingdom birth ratio is within normal limits, analysis of birth data for the calendar years from 2007 to 2011 has found the gender ratios at birth vary by mothers' country of birth," said health minister Earl Howe, the Telegraph reported.
The PD:control birth ratio showed a significant correlation with the crude influenza mortality for the year of birth during the period from 1900 to 1930 (Mattock et al.
The abortion to birth ratio was adjusted following a procedure suggested by Singh and Wulf to account for spontaneous abortion (10).
Right now, the World Health Organization estimates the male to female birth ratio in China at 117 to 100, whereas the statistical norm is 106 to 100.
Declining Minamata male birth ratio associated with increased male fetal death due to heavy methylmercury pollution.
There was no significant difference in the birth ratio of infants born to exposed and unexposed mothers (del Rio Gomez et al.
The issue of "missing girls" - manifested in birth ratios strongly skewed in favor of boys - has received significant attention at a global level over the past few decades.
"Replacing Myths with Facts" presents a review of existing studies on birth ratios and disproves myths about the practice of sex-selective abortion in the Asian American community.
Specific Chinese regions lead the way in terms of curious birth ratios, but prenatal sex-selection isn't a localised phenomenon.