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Topic: Heritability

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Twin study

Nature versus nurture

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Grenville Davey

Sympatry

Biological determinism

	Heritability -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-11-06)
		Heritability, as used professionally in (The branch of biology that studies heredity and variation in organisms) genetics, has a very precise definition.
		Estimating heritability is not a simple process, however, since only P can be observed or measured directly.
		However, the conclusions from studies involving intelligence tests often conclude that intelligence is highly heritable, because the tests are contrived so that it is (supposed to be) impossible to study so as to improve performance in them, and also because what ‘heritability’ actually means gets distorted in the re-telling in the popular media.
	www.absoluteastronomy.com /encyclopedia/h/he/heritability.htm (348 words)

	Heritability
		Heritability is a statistic used to evaluate animals and to predict response to selective breeding.
		Heritability is a ratio that describes the amount of phenotypic variation that can be attributed to the differences in the "additive genetic merit" of individuals in a population.
		Heritability in the broad sense is 1, but heritability in the narrow sense is less than 1, how much so depends on the relative magnitude of the additive and dominance variance.
	www.workingdogs.com /doc0189.htm (1785 words)

	"How Heritability Misleads about Race" by Ned Block
		Heritability, by contrast, is a matter of what causes differences in a characteristic: heritability of number of toes is a matter of the extent to which genetic differences cause variation in number of toes (that some cats have five toes, and some have six).
		Heritability studies of IQ within White populations in the US and northern Europe have tended to yield moderately high heritabilities: Herrnstein's and Murray's 60 percent is a reasonable figure.
		Heritability in that population would be zero because the ratio of genetic variation to total variation is zero if the genetic variation is zero.
	www.nyu.edu /gsas/dept/philo/faculty/block/papers/Heritability.html (6981 words)

	Using Heritability for Genetic Improvement
		Heritability is a measure of the degree (0 to 100%) to which offspring resemble their parents for a specific trait.
		Heritability is one important component of the equation used to predict genetic progress from selection to improve a trait.
		Heritability of interval to first luteal activity is higher than for interval to first breeding because cow behavior, missed heats, or management decisions have less effect on total variation between cows.
	www.ext.vt.edu /pubs/dairy/404-084/404-084.html (2130 words)

	Twin studies
		This is expressed as a percentage known as ‘heritability’ - for example, asthma has a heritability of 60 per cent, and insulin-dependent diabetes mellitus 70 per cent, indicating a strong genetic predisposition.
		For example, a heritability estimate of 70 per cent for ‘obesity’ does not mean that 70 per cent of any one person's obesity is somehow due to his/her genes and the other 30 per cent to his/her environment or that they have a 70 per cent risk of disease.
		Another common confusion is to equate the heritability of a trait and the number of genes that may influence it – as is often done in headlining the results of twin research.
	www.wellcome.ac.uk /en/genome/genesandbody/hg08b001.html (510 words)

	ARS \| Publication request: Heritability of Resistance to Aphanomyces Euteiches Races 1 and 2 in Alfalfa (Site not responding. Last check: 2007-11-06)
		We calculated heritability estimates for resistance to A. euteiches in alfalfa and found that over 80% of the trait was controlled by genetics for form 1, while over 60% of resistance to form 2 was controlled by genetics.
		Heritability on a half-sib progeny means basis was calculated based on data from pathogenicity tests conducted under greenhouse conditions.
		Heritability estimates based on experiments conducted over two years were high for all populations, ranging from 0.84-0.90 for resistance to A. euteiches race 1 and from 0.62-0.66 for resistance to A. euteiches race 2.
	www.ars.usda.gov /research/publications/publications.htm?SEQ_NO_115=159313 (553 words)

	Gene Expression: What is Heritability?
		Heritability of stature in a West African population is calculated from longitudinal data collected over 26 years...The heritability estimate of 0.6 appears lower than that from studies in European populations.
		Again, note that heritability estimates tend to be lower for a given population in the undeveloped world than to a genetically similar population in the developed world because of the much higher degree of environmental variance.
		In this study heritability of CC size was assessed by comparing the concordance of CC midsagittal area in 14 monozygotic and 12 dizygotic twin pairs with a mean age of 27 years, using magnetic resonance imaging and various methods of calculating trait heritability.
	www.gnxp.com /MT2/archives/002237.html?entry=2237 (1992 words)

	G2910 Heritability and Its Use in Animal Breeding, MU Extension
		Heritability measures the relative importance of hereditary and environmental influences on the development of a specific quantitative trait.
		The numerical value of the heritability estimate is given as a percentage or a decimal and should, of course, lie between 0 and 1.
		Second, the amount of genetic progress is also dependent on how highly heritable a trait is. Though the parents had an advantage over the herd average of 0.60 pounds per day in gain, they would not have transmitted any of this advantage to their offspring if the trait had a herd heritability.
	muextension.missouri.edu /xplor/agguides/ansci/g02910.htm (1695 words)

	Heritability estimates for carcass traits of cattle: a review (Site not responding. Last check: 2007-11-06)
		The unweighted means of estimates of heritability for 14 carcass traits by slaughter end point (age, weight, and fat depth) were calculated.
		However, heritability estimates for most traits varied greatly, which could be due to differences in breed groups, methods of estimation, effects in the model, number of records, measurement errors, sex, and management.
		Results from such studies have been inconsistent, although some studies revealed that heritability estimates for several carcass traits are sensitive to the covariate included in the model for the end point, implying that direct response to selection would be different for some traits depending on slaughter end point.
	funpecrp.com.br /GMR/year2004/vol3-3/gmr0102_abstract.htm (258 words)

	Understanding genetics - Heritability (Site not responding. Last check: 2007-11-06)
		Heritability can be defined as the efficiency of transmission of superiority (or inferiority) of a trait from parents to offspring.
		A trait that is 100% heritable would truly be a case of "what you see is what you get" as 100% of the trait or genotype will be expressed in the animal’s phenotype, or the way the animal looks.
		Knowledge of the heritability of traits that are important to the animal breeder is one of the essential parameters needed when planning a successful breeding program.
	www.dpi.qld.gov.au /beef/3139.html (651 words)

	Users\DOUG\WEBDEV\283-11 (Site not responding. Last check: 2007-11-06)
		Heritability refers to the extent to which a phenotypic trait is under genetic control.
		The question of heritability of phenotypic traits is exactly the basis for the nature vs. nurture debates that have surrounded study of traits such as human intelligence, aggression, homosexuality, and creativity.
		Narrow-sense heritability is estimated by comparing the mean phenotype of parents (the mid-parent value) to the mean phenotype of their progeny across a number of families.
	bioweb.wku.edu /Courses/Biol283/283-11.htm (1030 words)

	Heritability (Site not responding. Last check: 2007-11-06)
		Heritability is a statistical ratio that estimates the proportion of observational differences in a characteristic that can be attributed to genetic influences.
		Broad sense heritability is the proportion of total phenotypic variance due to all sources of genetic variance.
		The heritability coefficients were a good indicator to the variation on the characteristics measured that were due to genetic differences.
	academic.uofs.edu /STUDENT/DEJESUSS2/HERITABILITY.HTML (817 words)

	Heritability
		Degrees of heritability and genetic correlations in the Hanoverian breed.
		The degree of heritability is a way to measure the genetic strength of a characteristic, up to which degree a characteristic will be passed on to the next generation.
		The heritability of the basic gaits lies between 26% (walk) and 37% (trot), an area which is very useful in breed issues.
	www.hanoverian.com /ludwigherit.html (1661 words)

	Zoology 304, Evolution
		The heritability of a trait refers to the proportion of phenotypic variance in the trait which is based on genetic variance.
		The observation that IQ shows high heritability is often used as a basis for a claim that racial differences in average IQ must be caused by genetic differences between the races.
		Estimates of heritabilities are only reliable for the population and environment in which they are measured.
	www.science.siu.edu /zoology/King/304/wk4.htm (1218 words)

	Heredity and Heritability
		The concept of “heritability” was introduced “to quantify the level of predictability of passage of a biologically interesting phenotype from parent to offspring” (Feldman, 151).
		If heritability is low and variation in height is due mostly to the environment, then monozygotic twins will be as different in height from one another as dyzygotic twins.
		Psychologists are interested in the contribution of genes to human psychological traits whereas evolutionary biologists use heritability measures to predict and measure the response of a trait to selection.
	www.science.uva.nl /~seop/archives/win2004/entries/heredity (5801 words)

	Heritability: Introduction (Site not responding. Last check: 2007-11-06)
		If the heritability of most human behaviors is in the range of.30 to.60, then the environmentability of most human behaviors will be in the range of.40 to.70.
		A heritability of.40 informs us that, on average, about 40% of the individual differences that we observe in, say, shyness may in some way be attributable to genetic individual difference.
		Heritability depends on the range of typical environments in the population that is studied.
	psych.colorado.edu /hgss/hgssapplets/heritability/heritability.intro.html (460 words)

	Re: Broad-sense Heritability/environmentality (Site not responding. Last check: 2007-11-06)
		Heritability in the narrow sense is the variation in the population attributable (in a statitstical sense) only to additive genetic variation; board sense heritability includs non-addative genetic variation as well.
		As we discussed in class, heritability is a local measure -- so if the population is undergoing selection, the heritability of a trait will change (usually it will go down, and the environmentality of the trait will go up, in cases of straight-forward directional selection).
		Similarly, if an environmental 'pressure' is released, then variation that was mainly environmental (due to the fact that the heritable element was being held constant by stabalizing selection and/or directional selection being limited by some constraint), one might expect heritability to go up, as the heritable variation is no longer being selected against.
	fp.bio.utk.edu /evo-eco/_discussion/00000090.htm (262 words)

	Heritability and Selection
		We can define heritability as how strongly inherited genes influence the final way a dog appears (phenotype) or conversely how strongly nutrition and other environmental factors affect the genes to influence the final phenotype or appearance.
		Conversely, a trait with high heritibility (such as coat color) is strongly influenced by which genes the dog possesses.
		Heritability can also be defined as the proportion of parental superiority which is transmitted to offspring.For example, in a previous article the inheritance of height was discussed.
	members.aol.com /IzatKK/inherit.html (1002 words)

	Heritability: it's all relative
		Heritability is one of the foundational concepts of behavioral genetics, but its meaning is not always clear.
		New research is making it increasingly obvious that the answer is: "It depends." Heritability, as the term is used by behavioral geneticists, is a statistical measure defined in relation to a particular environment and a particular population.
		Their study explored the heritability of children's IQ in different populations within the United States--those with high socioeconomic status (SES) and those with low SES.
	www.apa.org /monitor/apr04/herit.html (453 words)

	Heritability of Developmental Enamel Defects in Primary Teeth (Site not responding. Last check: 2007-11-06)
		Objective: To determine the prevalence and heritability of enamel opacity and enamel hypoplasia in twins.
		Heritability analyses were pursued using the suite of genetic analysis modules in the SOLAR computer software package.
		Heritability was treated in its narrow sense as the contribution of additive genetic factors on phenotypic expression.
	iadr.confex.com /iadr/2004Hawaii/techprogram/abstract_47561.htm (265 words)

	Heritability does not tell you about genetic determinism
		The misuse of heritability measurements is widespread; even Hartl and Clark (the authors of a well-known quantitative genetics 101 textbook) appear to misunderstand the term (which is born from quantitative genetics in the first place!)
		When talking about how heritability estimates in twin studies in humans are highly flawed, Hartl and Clark say that "the effect of correlated environments has the effect of inflating the degree to which traits are genetically determined," implying that traits with a high heritability are highly genetically determined (441).
		Heritability, on the other hand, tells you only that different genotypes have different phenotypes from one another in the environments that you tested them in.
	fp.bio.utk.edu /evo-eco/_discussion/00000131.htm (347 words)

	NSIF-FS8
		Heritability (h to the 2nd power) is simply defined as that portion of the observable variation in a trait that is due to genetic control or breeding value.
		A trait with a high heritability means that an animal's own performance is a good estimate of its breeding value for the trait.
		With lowly heritable traits the individual performance and breeding value are poorly related and the performance of the individual will not be a very accurate indicator of its breeding value.
	www.ces.purdue.edu /extmedia/NSIF/NSIF-FS8.html (2385 words)

	Estimates of heritability in a blanched asparagus population (Site not responding. Last check: 2007-11-06)
		To estimate the heritability values of characters frequently used as selective criteria, 32 half-sib families obtained from selected plants of three populations of the asparagus variety Argenteüil were evaluated in a randomized complete block design.
		The values of realized heritability for most of the variables were moderate to high (between 0.18 and 0.68), except for days to emergence; lower values were obtained by the regression method.
		As there was a high degree of heritability, additive genetic factors contributed significantly to the genetic variance, which would allow the selection of phenotypically superior plants for asparagus improvement projects.
	funpecrp.com.br /GMR/year2002/vol1-1/gmr0007_abstract.htm (203 words)

	Foreign Dispatches: Heritability, Lies and Stupidity
		Anybody who says something like "the heritability of IQ is 0.50" without in any way qualifying that figure to a particular population under particular circumstances is therefore a liar or an idiot, and probably both.
		That those who love to rant about heritability never bother to state just what kind of heritability they're talking about is yet another giveaway that one is dealing with ignorant cranks with just the minimum familiarity with genetics to provide them with a veneer of scientific plausibility.
		I've chosen to touch here only on the issue of heritability because I'm pressed for time, but the truth is that all the arguments of the usual VDARE crowd are shot through with the same half-digested nonsense, usually carefully padded out with verbose bafflegab to disguise the intellectual emptiness of the argument being propagandized.
	reti.blogspot.com /2004/06/heritability-lies-and-stupidity.html (691 words)

	Lecture 1, Genetics (Site not responding. Last check: 2007-11-06)
		Heritability is the proportion of a population's overall variance that is due to genetic factors.
		In agriculture and animal science, measures of heritability are essential for selective breeding programs; programs that are designed to produce plants or animals with specific desirable traits, such as greater kernel size, unusual coat color, or increased disease resistance.
		The term heritability is also used in a more specific sense to refer to that proportion of the total variance that is contributed by additive alleles, as opposed to alleles that are completely dominant or subject to epistatic interactions.
	www.utpb.edu /scimath/kovalick/genetics/lecture9.htm (1719 words)

	Why is the heritability of adaptations generally zero?
		Heritability means that variation in some trait (like the presence or absence of homosexuality) is correlated with genetic variation (e.g., the presence or absence of some gene).
		Heritability is the proportion of variance in a phenotypic trait that is accounted for by genetic variance.
		Although vision is not heritable, if a particular visual performance parameter were measured precisely enough, a small degree of heritability in that parameter could no doubt be detected.
	www.anth.ucsb.edu /projects/human/epfaq/heritability.html (888 words)

	Gene Expression: Heritability as engineering tool
		You could also estimate heritabilities for categorical or ordinal traits like "Firm" vs. "Not Firm", but that makes the analysis more difficult (for one thing, it makes it harder to map QTLs).
		In other words, heritability determines the strength of the response to artificial or natural selection.
		However, the point that is usually missed is that a high environmental variability means that estimates of heritability in such an environment are lower bounds on the potential value.
	www.gnxp.com /MT2/archives/002526.html (1409 words)

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