Exam #1 W 2/6 in class Review T 2/5 from 5-7pm in PAI 3.02

PhenotypeGenotype Dominant Recessive

PhenotypeGenotype 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:

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 (BMI)% Biological siblings34 Parents and children living together26 Identical twins reared together80 Identical twins reared apart72 Fraternal twins reared together43 Adopted children and parents 4 Unrelated children living together 1 *But food preference shows little genetic correlation Correlation of weight and relatedness 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 pp 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 twice87 Identical twins reared together86 Identical twins reared apart76 Fraternal twins reared together55 Biological siblings47 Parents and children living together40 Parents and children living apart31 Adopted children living together 0 Unrelated people living apart 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 twice87 Identical twins reared together86 Identical twins reared apart76 Fraternal twins reared together55 Biological siblings47 Parents and children living together40 Parents and children living apart31 Adopted children living together 0 Unrelated people living apart 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: , 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): )

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.

Fig 2. BIRTH WEIGHT, SEXUAL ORIENTATION AND THE SEX OF PRECEDING SIBLINGS (2001) RAY BLANCHARD AND LEE ELLIS J. biosoc. Sci. 33, 451–467 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.

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.

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) Finger length and Homosexuality

Both nature and nurture determine human sexuality. Is one more of a choice?