Concept explainers
To analyze:
Human MZ and DZ are the twin pairs of the same sex reared together are studied and the following concordance values are identified for various traits. Depending on the values shown in the table, explain the relative importance of genes versus the influence of environmental factors for each trait.
Trait | Concordance | |
MZ | DZ | |
Blood type | ||
Chicken pox | ||
Manic depression | ||
Schizophrenia | ||
Diabetes | ||
Cleft lip | ||
Club foot |
Introduction:
Monozygotic twins (MZ) are the ones who prepared from one zygote, which splits and forms two embryos. In dizygotic twins (DZ), each twin develops from each egg is fertilized by a dissimilar sperm and a separate egg. To estimate the influence of genes on phenotypic variation, the study of identical twins reared together can be carried out. In such studies, concordance is measured. Concordance is the percentage of twin pairs in which both members of the pair have the same phenotype for a trait. Concordance frequency gives a general picture of the overall influence of genes on phenotypes.
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Genetic Analysis: An Integrated Approach (3rd Edition)
- The following table gives the percentage of twin pairs studied in which bothtwins expressed the same phenotype for a trait (concordance). Percentages listedare for concordance for each trait in monozygotic (MZ) and dizygotic (DZ) twins.Assuming that both twins in each pair were raised together in the sameenvironment, what do you conclude about the relative importance of genetic (H)versus environmental (E) factors for each trait?Traits MZ, % DZ, % H EBlood types 100 66Eye color 99 28Measles 95 87Diabetes 65 18Mental retardation 97 37arrow_forwardMany researchers have estimated the heritability of human traits by comparing the correlation coefficients of monozygotic and dizygotic twins (see pp. 731–732). One of the assumptions made in using this method is that monozygotic twin pairs experience environments that are no more similar to each other than those experienced by dizygotic twin pairs. How might this assumption be violated? Give some specific examples of how the environments of two monozygotic twins might be more similar than the environments of two dizygotic twins.arrow_forwardWhich of the following best describes the broad-sense heritability of a trait? Variance in the trait that is due to genetic effects (VG) The proportion of phenotype variance that is due to genetic effects (VG/Vp) The proportion of phenotype variance that is due to genetic effects (Vp - VG) The proportion of phenotype variance that is not due to genetic effects (Vp- VE) the degree to which genes influencing a trait are passed from offspring to parents Toarrow_forward
- The following table gives the percentage of twin pairs studied in which both twins expressed the same phenotype for a trait (concordance). Percentages listed are for concordance for each trait in monozygotic (MZ) and dizygotic (DZ) twins. Assuming that both twins in each pair were raised together in the same environment, what do you conclude about the relative importance of genetic (H) versus environmental (E) factors for each trait? Trait MZ % DZ % Blood types 100 66Eye color 99 28 Measles 95 87 Diabetes 65 18Mental retardation 97 37arrow_forwardClubfoot and spina bifida are traits best explained by the Threshold Model of complex traits. The Threshold Model explains the distribution of some complex traits. Only those individuals who have a genetic liability above a certain threshold are affected if exposed to certain environmental factors, such as continuous; maternal age continuous; maternal nutrition discontinuous; maternal nutrition discontinuous; maternal intelligence none of these are correctarrow_forwardThe graphs below show antibiotic production from the same population of bacteria, grown in two different environments-high glucose and low glucose. Number of organisms HIGH GLUCOSE LOW GLUCOSE Amount of antibiotic produced If you calculate the heritability of antibiotic production for this population of bacteria when grown in low glucose compared to when it is grown in high glucose, the estimated heritability value Incorrect will be smaller in the low glucose than in the high glucose. will not be possible to estimate because you don't know the genotypic variation. will be larger in the low glucose than in the high glucose. will be the same in both environments. X Xarrow_forward
- QTL mapping and GWA (association) mapping are two different methods used to identify genes that affect complex traits. For each of the following statements, choosewhether it applies to QTL mapping, association mapping, or both.whether it applies to QTL mapping, association mapping, or both.arrow_forwardA geneticist studies a series of characteristics in pairs of monozygotic and dizygotic twins, obtaining the concordances listed below. For each characteristic, indicate whether these concordances suggest genetic influences, environmental influences, or both. Explain your reasoning. Concordance (%) Dizygotic Characteristic Monozygotic Migraine headaches 60 30 Eye color 100 40 Measles 90 90 Club foot 30 10 High blood pressure 70 40 Handedness 70 70 Tuberculosisarrow_forwardDraw the expected phenotypic variance of a trait encoded by 5 genes with 25% environmental variance vs. a trait encoded by 5 genes with 2% environmental variance.arrow_forward
- The following table gives the percentage of twinpairs studied in which both twins expressed the same phenotypefor a trait (concordance). Percentages listed arefor concordance for each trait in monozygotic (MZ) anddizygotic (DZ) twins. Assuming that both twins in eachpair were raised together in the same environment, whatdo you conclude about the relative importance of geneticversus environmental factors for each trait?arrow_forwardADHD is a highly heritable trait with published broad sense heritability estimates in the range of 0.6- 0.9. Larsson et al. 2014 (doi: 10.1017/S0033291713002493 ) reported the concordance values shown in the table below for pairs of monozygotic (MZ) or dizygotic (DZ) twins with data for male and female pairs shown separately, using data from the Swedish twin register (59,000 twin pairs, born between 1959 and 2001). Male MZ twins Male DZ twins Female MZ twins Female DZ twins 56% 16% 37% 13% Based on the data in this table, does ADHD appear to be more heritable in males or females? Provide one sentence of rationale to support your answer.arrow_forwardTwin studies are often used in the research of human behavioral traits. Although helpful, there are limitations to these studies. All of the following are limitations to twin studies EXCEPT: Traits are assumed to be simple Mendelian inheritance, discounting additive alleles and epistasis Dizygotic twins will often share more than 50% of their genes Monozygotic twins are often treated more similarity than dizygotic twins O Twins studies are a mechanism to understand the genetic and environmental components of a trait Twins reared apart are often adopted out to families of similar income, ethnicity, and religionarrow_forward
- Human Heredity: Principles and Issues (MindTap Co...BiologyISBN:9781305251052Author:Michael CummingsPublisher:Cengage Learning