Download Correlation of IQ Inheritance

Exam #1 W 2/6 in class
Review T 2/5 from 5-7pm
in PAI 3.02
Genotype
Phenotype
Dominant
Recessive
Genotype
Phenotype
Genes code for
proteins (or RNA).
These gene
products give rise
to traits…
It is rarely this
simple.
What makes us
who we are?
Nature and
Nurture
Based on “Nature via Nurture” by Matt Ridley (2003)
Imprinting:
exposure to movement
(environment) sets
“mother”
X/Y chromosomes
in humans:
genes = traits
Twin studies have been used to determine
the heritability of various traits.
Types of twins:
http://pennhealth.com/health_info/pregnancy/000199.htm
Twin studies have been used to determine
the heritability of various traits, but there
are some caveats:
How many twins have been studied?
How different are the environments?
Correlation of weight and relatedness
Correlation of weight (BMI)
%
Biological siblings
34
Parents and children living together 26
Identical twins reared together
80
Identical twins reared apart
72
Fraternal twins reared together
43
Adopted children and parents
4
Unrelated children living together
1
*But food preference shows little genetic
correlation
The nature of environmental influences on weight and obesity: A behavior genetic analysis. Grilo, Carlos M.;
Pogue-Geile, Michael F.; Psychological Bulletin, Vol 110(3), Nov 1991. pp. 520-537. And two books by
Matt Ridley: Nature via Nurture (2003) and Genome: the Autobiography of a Species in 23 Chapters (1999)
Intelligence
Correlation of IQ Inheritance :
The same person tested twice
Identical twins reared together
Identical twins reared apart
Fraternal twins reared together
Biological siblings
Parents and children living together
Parents and children living apart
Adopted children living together
Unrelated people living apart
%
87
86
76
55
47
40
31
0
0
From two books by Matt Ridley: Nature via Nurture (2003) and Genome: the Autobiography of a Species in 23 Chapters (1999)
When the
environment is
equal (everyone has
access to resources),
genetic differences
are magnified.
When environments
are different (only a
few have access to
resources),
environmental
differences are
magnified.
Proof or disproof?
Correlation of IQ Inheritance :
The same person tested twice
Identical twins reared together
Identical twins reared apart
Fraternal twins reared together
Biological siblings
Parents and children living together
Parents and children living apart
Adopted children living together
Unrelated people living apart
%
87
86
76
55
47
40
31
0
0
From two books by Matt Ridley: Nature via Nurture (2003) and Genome: the Autobiography of a Species in 23 Chapters (1999)
Children of alcoholic parents are likely to
become alcoholics…
Children of abusive parents are likely to
become abusive…
…Nature or Nurture?
What about Human
Sexuality?
Occurrence of homosexuality among brothers:
* 52% of identical twins of homosexual men were
also homosexual
* 22% of fraternal twins were also homosexual
* 11% of adoptive brothers of homosexual men were
also homosexual
(J.M. Bailey and R.C. Pillard, "A genetic study of male sexual orientation," Archives of General Psychiatry, vol. 48:1089-1096, Dec 1991.)
Occurrence of homosexuality among sisters:
* 48% of identical twins of homosexual women
were also homosexual
* 16% of fraternal twins were also homosexual
* 6% of adoptive sisters of homosexual women were
also homosexual
(Bailey, J. M. and D. S. Benishay (1993), "Familial Aggregation of Female Sexual Orientation," Am. Journal of Psychiatry 150(2): 272-277.)
While there appears to be a genetic component
to homosexuality, identifying the genes
involved has been difficult.
Environmental effects may also play a
role in determining sexuality.
Birth order: Each elder brother increases
probability of homosexuality by 1/3.
Environmental effects on homosexuality
Birth order: Each elder brother increases
probability of homosexuality by 1/3.
Birth weight:
Boys born as third sons have lower birth
weight.
Birth Weight, Sexual Orientation and the Sex of Preceding
Siblings
Fig 2. BIRTH WEIGHT, SEXUAL ORIENTATION AND THE SEX OF PRECEDING SIBLINGS (2001) RAY
BLANCHARD AND LEE ELLIS J. biosoc. Sci. 33, 451–467
Homosexual males with older brothers have a lower birth
weight.
Fig 2. BIRTH WEIGHT, SEXUAL ORIENTATION AND THE SEX OF PRECEDING SIBLINGS (2001) RAY
BLANCHARD AND LEE ELLIS J. biosoc. Sci. 33, 451–467
Environmental effects on homosexuality
Birth order: Each elder brother increases
probability of homosexuality by 1/3.
Birth weight:
Boys born as third sons have lower birth
weight.
Mothers may have immune reaction
against male proteins.
Finger Length and Homosexuality
NATURE VOL 404 pg 455 (30 MARCH 2000)
Finger length and Homosexuality
NATURE VOL 404 pg 455 (30 MARCH 2000)
Finger length and
Homosexuality
NATURE VOL 404 pg 455 (30 MARCH 2000)
Both nature and nurture
determine human
sexuality.
Is one more of a choice?