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- Larsson, Mats, et al.
(författare)
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Importance of genetic effects for characteristics of the human iris
- 2003
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Ingår i: Twin research. - : Cambridge University Press (CUP). - 1369-0523 .- 2053-6003 .- 0000-0000. ; 6:3, s. 192-200
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Tidskriftsartikel (refereegranskat)abstract
- The relative importance of genetic influences (heritability) on five general textural quality characteristics of the human iris was assessed using sex and age limitation models. Colour photographs of irises were available from 100 monozygotic twin pairs, 99 dizygotic twin pairs, and 99 unrelated randomly paired age-matched German subjects. Comparative scales were constructed and two judges who were blind to zygosity independently rated five characteristic of the subjects' left iris. Inter-rater reliabilities were larger than .90 for all five scales. The heritabilities for the five iris characteristics ranged from .51-.90. No sex-specific genetic factors were found for the iris characteristics. Age-group differences in heritability were found for one of the five iris characteristics — "distinction of white dot rings". Heritability was greater for the older cohort (90%) than the younger (73%). The iris characteristics that showed the next highest additive-genetic effect were "contractional furrows" (78%) and "frequency of crypts" in the main stroma leaf (66%).
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| 3. |
- Lichtenstein, Paul, et al.
(författare)
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Remembered Parental Bonding in Adult Twins: Genetic and Environmental Influences
- 2003
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Ingår i: Behavior Genetics. - 0001-8244. ; 33:4, s. 397-408
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Tidskriftsartikel (refereegranskat)abstract
- One common assumption in psychology is the impact of parenting and parent-child relationships on the child's adjustment throughout the life span. Studies have indicated that there are genetic influences on memories of parenting, but how these influences are mediated has not typically been investigated. A sample of 150 pairs of monozygotic and 176 pairs of dizygotic Swedish twin women reported on personal characteristics and on remembered relationships with their mother and father using the Parental Bonding Instrument (PBI). Quantitative genetic analyses showed moderate genetic influences for remembered parental warmth, which also was partly explained by genetic influences for optimism, aggression, and humor. The other two PBI scales, authoritarianism and protectiveness, showed only shared and nonshared environmental influences. One interpretation of the findings is that heritable personal characteristics of children elicit parental warmth. However, other explanations such as personality characteristics influencing how experiences with parents are interpreted or circumstances in adult life that affect the recall of experiences could not be ruled out.
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