1. Messinger Genetics and Prenatal Development PSY344W D. Messinger, Ph.D. Psychology of Infancy

2. Messinger Class n What are the advantages (name some forms of genetic transmission) and disadvantages of thinking of genes as blueprints? n How do environmental and genetic influences interact during prenatal development (provide examples)? n What is the difference between transactional and a behavioral genetics approach to gene * environment interactions?

3. Messinger Who believes in n Nature – genetics – Genes as blueprint n Nurture – environment – Infinite malleability n Genes and environment working interdependently and interacting?

4. Messinger Some basics n Genes – Bits of DNA, protein, in each cell – contain information on cell functioning, production, and reproduction n Chromosomes – Larger groupings of DNA – All non-gamete cells in the body have 23 pairs of chromosomes – Half of each pair came from each parent

5. Messinger Chromosomes Reality Ordered by karotyping

6. Messinger Human genome project n identify all the approximately 30,000 genes in human DNA, n determine the sequences of the 3 billion chemical base pairs that make up human DNA, n 99.9% (of nucleotide bases) are the same in all people

7. Messinger Chromosome 19

8. Messinger Genomes to Life Project n Identify the protein machines that carry out critical life functions and the gene regulatory networks that control these machines

9. Messinger Terms n Phenotype – Observable trait n Genotype – Genetic pattern associated with the phenotype

10. Messinger How are genes a blueprint? n “The DNA sequence (e.g., ATTCCGGA)... spells out the exact instructions required to create a particular organism with its own unique traits.” n A metaphor which describes some aspects of phenomenon – Specific correspondences between genotype and phenotype

11. Messinger Blueprint-like modes of genetic transmission n Dominant-recessive – Single gene or Mendellian n Specific genetic defects can be deadly or disabling n http://www.uaf.edu/psych/psyc240/exam1/index.html, Jim Allen, Ph.DJim Allen – Phenylkitenuria, sickle cell, etc. n Sex-linked (23rd chromosome)

12. Messinger Dominant-Recessive Inheritance n Traits are transmitted as separate units n Autosomes - 22 pairs – Non-sex chromosomes – One pair from each parent n When 2 competing traits are inherited – Only 1 trait is expressed n Dominant trait n Recessive trait

13. Messinger Dominant-Recessive Inheritance Traits are transmitted as separate units 25% risk of inheriting a “double-dose” of r genes which may cause a serious birth defect 25% chance of inheriting two N’s thus being unaffected 50% chance of being a carrier as both parents are

14. Messinger Sex-linked inheritance n 23rd chromosomal pair n Female = XX – each branch is matched n Male = XY (Missing an arm) – one Y branch not matched – so allele on corresponding X branch is expressed

15. Messinger Sex-linked inheritance n Male’s “x” inherited from mother – Women are carriers – Males represented disproportionately in sex linked disorders n baldness color-blindness, hemophilia – Baldness: maternal gf > f n Even sex-linked characteristics are dependent on environmental influences – Expression of baldness depends on circulating testosterone levels

16. Messinger Polygenic inheritance – not blue- print like - is the rule n Multiple genes influence most traits n Sign of polygenic inheritance is range in phenotype rather than either or – skin/eye/hair color, height, baldness, personality – Reaction Range – Potential variability in expression of a trait n Such traits may also be susceptible to environmental influence

17. Messinger Putting genes in their environment n Meiosis – Each pair splits – Producing gamete with unique set of chromosomes n Gametes - sex cells – Sperm – Ovum n Fertilization of the ovum creates the zygote - New Cell

18. Messinger Disadvantages of the genes-as- blueprint metaphor n Genes are bits of protein in a primarily liquid nucleus in a primarily liquid cell surrounded by other cells in a primarily liquid uterine environment – Without an “environment,” genes are bits of protein n From a lump of jelly to an organism – How do genes actually work?

19. Messinger Prenatal development is usually divided into three main periods. n Zygote - – covers the first two weeks after conception – ends when the zygote implants into the wall of the mother's uterus. n Embryo - – from two to eight weeks following conception – the major organs and bodily systems form n Fetus – from eight weeks after conception until birth – grows tremendously in size and weight.

20. Messinger Zygotic cell differentiation

21. Messinger From zygote to embryo

22. Messinger The question n The zygote grows through cell division – Mitosis - One for one copying of all 23 chromosomes n All cells contain the same genetic information in their nuclei n But qualitatively different types of cells develop in different parts of the body n How does this occur?

23. Messinger General processes yield specific outcomes n Cells clump together as a sphere n This changes the extra-cellular environment of cells on the inside and outside of the sphere n Differences in environment impact cell’s genetic make-up to activate different proteins

24. Messinger Gene x Environment interaction n Environmental factors influence development from the start – Cells are environments – The uterus is an environment n The fetus participates in actively constructing its own development – it is not passively constructed

25. Messinger Creation of a tube

26. Messinger Embryology n Cells groups in which specific molecular processes occur with boundaries with other groups n Regulator genes activate and de-activate other genes within these groups n Cells impact each other such that a nerve cell transplanted to the liver region becomes a liver cell after several replications – Stem cell debate

27. Messinger Period of the fetus n from eight weeks after conception until birth n grows tremendously in size and weight. n recognizable human shape n though it still weighs less than an ounce.

28. Messinger Brain development n General pattern of brain development genetically specified – By 20 weeks, most neurons present – 3rd - 16th prenatal week most crucial – At 8 weeks, head is half of fetus n But specific connections depend on generic growth processes and sensory-motor stimulation – Trillions of connections still forming – Trimming of these connections is developmental task

29. Messinger The fetus as actively constructing its own development n Fetal behavior impacts physical development – In chicks prevented from moving, cartilage turns to bone n Fetal sensory experience impacts sensory development – Mice whose tongues were anesthetized had malformed cleft palates

30. Messinger Prenatal sensory experience impacts sensory development n Hearing typically develops before sight n Rats, ducklings, and quail chicks exposed to visual stimulation prenatally – before they normally would n lose hearing ability at birth n Normal sensory development contingent on extra-fetal environment – being enclosed

31. Messinger Prenatal behavioral development n 9 weeks - movement n 16 weeks - frowning, grimacing n 25 weeks - moves to drumbeat n 26 weeks - remembers sounds n 32 weeks - all brain areas functioning n 34 weeks - can habituate

32. Messinger 2 perspectives on gene*environment interface n Transactional – “It is not nature vs. nurture, but the interaction of nature and nurture that drives development.” Urie Bronfrenbrenner (what we just heard) n Quantitative – The influence of genetic and environmental factors be distinguished and the influence of each can be quanitified using behavioral genetic methods (Plomin)

33. Messinger Behavioral genetics n Measuring genetic and environmental influences on behavior n Finding genes for behaviors?

34. Messinger Sources of Variance in Behavior n Genetic (heritability) n Environmental n Gene x environment interaction n Error

35. Messinger Estimates of genetic and environmental influence n Proportional in samples – Greater environmental variation n Will minimize genetic variation – E.g. Poverty – Greater genetic variation n Will minimize environmental variation – E.g. Downs Syndrome

36. Messinger Trivia n Why might adoption studies maximize estimates of genetic influence? n Can genetic effects increase with time? – How?

37. Messinger Environmental effects n Previously modeled but not measured n Now parental monitoring, neighborhood deprivation account for small (2-5%) of environmental variation – What else should we be measuring?

38. Messinger Twin Studies Monozygotic vs Dizygotic: human studies of genetic versus environment

39. Messinger Twin studies Identical (MZ) twins share 100% of their genes – genetic duplicates. Fraternal (DZ) twins share 50% of their genes – on average Both types of twins have similar environments... n Greater behavioral similarity of identical twins indexes greater genetic influence http://www.psych.umn.edu/psylabs/mtfs/special.htm

40. Messinger Gene * Environment interactions n Development always involves this interaction n Specific statistical effects – Genetic effects on alcohol use are great in non-religious than religious households – Genetic effects on seeking specific environments – n Identical twins find similar friends n Identical twins treated more similarly (or differently) than fraternal twins?

41. Messinger No genetic influence

42. Messinger Complete genetic influence

43. Messinger Additional readings n Plomin, et al. The genetic basis of complex human behaviors. n Plomin, R., & Rutter, M. (1998). Child development, molecular genetics, and what to do with genes once they are found. Child Development, 69(4), 1223-1242. n Rutter. M. (in press [2002]. Nature, nurture, and development: From evangelism through science towards policy and practice. Child Development. n Collins, W. A., Maccoby, E. E., Steinberg, L., Hetherington, E. M., & Bornstein, M. H. (2000). Contemporary research on parenting: The case for nature and nurture. American Psychologist, 55(2), 218-232. n Sleigh, M. J., Columbus, R. F., & Lickliter, R. (1998). Intersensory experience and early perceptual development: Postnatal experience with multimodal maternal cues affects intersensory responsiveness in Bobwhite Quail Chicks. Developmental Psychology, 34(2), 215-223.

44. Messinger Class n Syllabus Syllabus