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Charles Darwin Film
                                        Series


                                                     ...
Behavioral Genetics:

    Phil/Biol 2510, Spring 2008
Behavioral Genetics
The branch of genetics that studies the role of
genetics in (complex) behavior, disentangling the
rela...
Outline
• Nature v. Nurture (Heritability)
• Types of Studies
  –Twin Studies
  –Linkage Studies
  –Association Studies
• ...
Outline
• Nature v. Nurture (Heritability)
• Types of Studies
  –Twin Studies
  –Linkage Studies
  –Association Studies
• ...
Pamela Burford & Patricia Ryan




• Identical twins (1954):
   – from same fertilized egg that split in early development...
What Accounts for these
         Similarities?
      NATURE: Twins share identical DNA

                      or

NURTURE:...
Okay, but…
Doesn’t it make sense to think that genes play a
greater or lesser role in determining specific
behavior?

This...
Heritability
• Heritability is measured by looking at
  variation within a group.

• Heritability is a number between 1 an...
Heritability




               http://www.mvskokefood.org/cornstalk.JPG
Heritability
Lets look at some corn plants




                                   http://www.mvskokefood.org/cornstalk.JPG
Heritability
                                   In the field, some are
Lets look at some corn plants        tall, and some...
Heritability
                                          In the field, some are
Lets look at some corn plants               ...
Heritability
Let’s grow a clone of one corn plant in the same field




                                                  ...
Heritability
Let’s grow a clone of one corn plant in the same field
                 What will happen?




               ...
Heritability
Let’s grow a clone of one corn plant in the same field


                               If they have the same...
Heritability
Let’s grow a clone of one corn plant in the same field




                                                  ...
Heritability
Let’s grow a clone of one corn plant in the same field

                                 If they have no vari...
Heritability
Let’s grow a clone of one corn plant in the same field




                                                  ...
Heritability
Let’s grow a clone of one corn plant in the same field
                                 If they have 50% as m...
Heritability
Let’s grow a batch of the original seeds in a greenhouse




                                                ...
Heritability
Let’s grow a batch of the original seeds in a greenhouse
                What will happen?




              ...
Heritability
Let’s grow a batch of the original seeds in a greenhouse


                              If they have the sam...
Heritability
Let’s grow a batch of the original seeds in a greenhouse




                                                ...
Heritability
Let’s grow a batch of the original seeds in a greenhouse

                                If they have no var...
Heritability
Let’s grow a batch of the original seeds in a greenhouse




                                                ...
Heritability
Let’s grow a batch of the original seeds in a greenhouse
                                 If they have 50% as...
Heritability

           Variation due to genes
H=
   Variation due to genes + environment
Heritability

                 Variation due to genes
      H=
         Variation due to genes + environment


• Heritabil...
Heritability

                 Variation due to genes
      H=
         Variation due to genes + environment


• Heritabil...
Heritability

                 Variation due to genes
      H=
         Variation due to genes + environment


• Heritabil...
Heritability
       • Heritability of:
                –economic risk attitude: 57%
                –hedonic capacity: 46%...
Outline
• Nature v. Nurture (Heritability)
• Types of Studies
  –Twin Studies
  –Linkage Studies
  –Association Studies
• ...
Outline
• Nature v. Nurture (Heritability)
• Types of Studies
  –Twin Studies
  –Linkage Studies
  –Association Studies
• ...
Outline
• Nature v. Nurture (Heritability)
• Types of Studies
  –Twin Studies
  –Linkage Studies
  –Association Studies
• ...
Strategy of Twin Studies
• Compares similarities and differences within a
  population; and between sub-groups within that...
Two Assumptions
1. Genetic Similarity: Identical twins (MT) are 100% genetically
   identical and fraternal twins (FT) are...
Minnesota Twin Studies, 1988




                        24
Minnesota Twin Studies, 1988
• Thomas Bouchard
  – Minnesota Study of Twins Reared Apart
  – 100s of twins separated at bi...
Minnesota Twins’ Personality
• Bouchard found that a host of personality traits were
  substantially affected by genes;

•...
What DO Twin Studies Tell Us?
• That behaviors (phenotypes) are a combination of both
  genetic and environmental influenc...
What DON’T Twin studies tell us?




                            27
What DON’T Twin studies tell us?

• NOT whether behavior is alterable
  – That is, whether genes are destiny.




        ...
What DON’T Twin studies tell us?

• NOT whether behavior is alterable
  – That is, whether genes are destiny.


• NOT whic...
What DON’T Twin studies tell us?

• NOT whether behavior is alterable
  – That is, whether genes are destiny.


• NOT whic...
Outline
• Nature v. Nurture (Heritability)
• Types of Studies
  –Twin Studies
  –Linkage Studies
  –Association Studies
• ...
Outline
• Nature v. Nurture (Heritability)
• Types of Studies
  –Twin Studies
  –Linkage Studies
  –Association Studies
• ...
Linkage Studies
• Looks for inheritance patterns of target behavior
  (phenotype) in a population (e.g., family tree) and ...
We need family trees to locate
          genes




                http://www.ucl.ac.uk/~ucbhjow/b241/mendel_1.html
We need known DNA
           differences
• Remember there are several million
  common differences in the human
  populati...
Tracking a phenotype in a
          family

         11         11




         Marker 1
Tracking a phenotype in a
          family

         11         11




         Marker 1
Tracking a phenotype in a
          family

         11         11


1    1    1              1   1   1



         Marker...
Tracking a phenotype in a
          family

          11         11


11   11    11             11   11 1 1




          ...
Tracking a phenotype in a
             family

                    11         11


11 1 1 11   11 11    11   11        11 ...
Tracking a phenotype in a
             family

                    11         11


11 1 1 11   11 11    11   11        11 ...
Tracking a phenotype in a
                family

                    11         11


11 1 1 11   11 11    11   11        ...
Tracking a phenotype in a
             family

                    11         11


11 1 1 11   11 11    11   11        11 ...
Tracking a phenotype in a
             family

                    11         11


11 1 1 11   11 11    11   11        11 ...
Tracking a phenotype in a
             family

                     11         11


11 1 1 11    11 11    11   11        1...
Tracking a phenotype in a
             family

                     11         11


11 1 1 11    11 11    11      11      ...
Tracking a phenotype in a
             family

                     11        11


11 1 1 11    11 11    11      11       ...
Tracking a phenotype in a
          family

         22         22




         Marker 2
Tracking a phenotype in a
          family

         22         22




         Marker 2
Tracking a phenotype in a
          family

         22         22


2    2    2              2   2   2



         Marker...
Tracking a phenotype in a
          family

          22         22


22   22    22             22   22 22



          Ma...
Tracking a phenotype in a
               family

                     22         22


22   22 22   22 22    22   22       ...
Tracking a phenotype in a
               family

                     22         22


22   22 22   22 22    22   22       ...
Tracking a phenotype in a
                   family

                         22         22


22       22 22   22 22    22...
Tracking a phenotype in a
                family

                          22         22


22        22 22   22 22    22 ...
Tracking a phenotype in a
                family

                      22         22


22    22 22   22 22    22   22    ...
Tracking a phenotype in a
                family

                        22         22


22    22 22     22 22    22   22...
Tracking a phenotype in a
                family

                        22         22


22    22 22     22 22    22     ...
Tracking a phenotype in a
                family

                        22        22


22    22 22     22 22    22      ...
Linkage and Sexual Preference
• Genes determine sex (XX or XY). Do they
  determine sexual preference? In the 1990s
  Dean...
Genes and Sexual Preference
• Hamer reasoned that if homosexual behavior has a strong genetic
  basis, then it would be pa...
Xq28
Found Marker on X Chromosome (Xq28):
  – Of the 40 pairs, 33 had five markers that were
    the same.


  – Concluded...
“Gay Gene”
Study received much attention*, both pro and con.

  – Newspapers reported on discovery of “Gay Gene”


  – 199...
What does Hamer’s study tell us?
• Not really a “gene” but a region of a chromosome.


• No identified causal pathway from...
Outline
• Nature v. Nurture (Heritability)
• Types of Studies
  –Twin Studies
  –Linkage Studies
  –Association Studies
• ...
Outline
• Nature v. Nurture (Heritability)
• Types of Studies
  –Twin Studies
  –Linkage Studies
  –Association Studies
• ...
Association Studies
                    (with Animals)

• Basic Strategy: Find gene of interest, and
  manipulate it to de...
Romantic Voles
    • Science 10 June
      2005. Study on
      variations in a gene
      promoter sequence
      that pr...
Romantic Voles
• Differences in promoter sequences in a particular gene
  drastically affects complex social behaviors.


...
Romantic Voles
• Researchers transferred a single gene
  from male prairie voles (which are
  monogamous) to male meadow v...
Romantic Mechanism?
• Mating releases dopamine in the brain, dopamine
  receptors are located in the brain’s pleasure cent...
Same genes are in operation in humans and other mammals




                                                     47
Same genes are in operation in humans and other mammals




                                                     48
Same genes are in operation in humans and other mammals




                                                     48
Same genes are in operation in humans and other mammals




                       RS3

• September 2008, Walum et al.
• N...
Vasopressin in Humans

• People were characterized on a
  Partner Bonding Scale to determine
  how happy their marriages w...
Vasopressin in Humans
  Threatened divorce in the last year
                solitary alleles
             0          1    ...
Love and Fos-B
In early 1995, an M.D-Ph.D student, Jennifer Brown,
was breeding mice with an inactivated form of the
gene ...
Fos-B and nurturing behavior
Twenty-four to forty-eight hours after delivery, the mortality rate of
  the pups was in exce...
With and without Fos-B




Images: http://www.med.harvard.edu/publications/On_The_Brain/Volume06/Number2/synaphshot.html

...
Outline
• Nature v. Nurture (Heritability)
• Types of Studies
  –Twin Studies
  –Linkage Studies
  –Association Studies
• ...
Outline
• Nature v. Nurture (Heritability)
• Types of Studies
  –Twin Studies
  –Linkage Studies
  –Association Studies
• ...
So, what about sexuality?
• Sexual behavior is complex
  –We looked at several sexual behaviors: sexual
   orientation, ma...
Single genes generally have
              small effects
0 Functional    0 Functional
                                     ...
Many genes affect multiple
                      phenotypes




Carried out a genome-wide association scan for variants as...
What about sex?
• Causal pathway is crucial
 –How do we get from gene to behavior?


                  ?


  Gene         ...
What about sex?
• Causal pathway is crucial
 –How do we get from gene to behavior?


                  ?


  Gene     mRNA...
What about sex?
• Causal pathway is crucial
 –How do we get from gene to behavior?



               Environment

  Gene  ...
Implications:
   Why study homosexuality?
• Curiosity about genetics of sexuality

• Evolutionary puzzle
  – If homosexual...
“Medicalization” of Behavior?
When normal behavior is increasingly viewed as
a disorder. Due to increasing commercial and
...
“Leave gay sheep alone.”
         • Researchers in Oregon propose studies
           on sheep regarding sexual partner
   ...
“Leave gay sheep alone.”
“How can it be that, in the year 2006, a major
university would host such homophobic and cruel
ex...
4 Difficulties with Behavioral
              Genetics
1. Defining and measuring behavior

2. No (single) “gene for X”:
  –...
Summary
• Tools of the Trade
  – Twin, linkage, and association studies
  – Heritability Estimates (nature v. nurture)
  –...
68
Charles Darwin Film
                                        Series


                                                     ...
Lecture 14 Behavioral genetics
Lecture 14 Behavioral genetics
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Transcript of "Lecture 14 Behavioral genetics"

  1. 1. Charles Darwin Film Series Evolution: Darwin’s Dangerous Idea Facilitator: Dr. Anya Plutynski Join the Marriott Library in celebrating Darwin’s 200th birthday with the film Evolution : Darwin’s Dangerous Idea. Evolutionary theory is featured in this film through the key moments in Darwin’s life and current research utilizing dramatization and documentary sequences. Dr. Anya Plutynski of the University of Utah’s Phi- losophy Department will introduce the film and be available for questions and answers. Her research Images from en.wikipedia.org specialization is in the history and philosophy of sci- ence, particularly evolutionary biology in the early 20th century. Date: March 4, 2009 Time: 1:00 p.m.—3:00 p.m. Place: Room 1120 Marriott Library Check http://darwin2009.utah.edu for more University of Utah and Marriott Library events. J. Willard Marriott Library Phone: 801-581-7533 University of Utah 801-585-7870 295 S. 1500 W. Salt Lake City, UT. 84112-0860 E-mail: robin.reid@utah.edu marie.paiva@utah.edu Organization
  2. 2. Behavioral Genetics: Phil/Biol 2510, Spring 2008
  3. 3. Behavioral Genetics The branch of genetics that studies the role of genetics in (complex) behavior, disentangling the relative contributions of genetics and environment in behavioral phenotypes. Looks for genetic links for complex behaviors including personality traits, addiction, mental disease, intelligence, anti-social behavior, sexuality, and more. (Psychiatric genetics, developmental psychology, ethology, etc. 4
  4. 4. Outline • Nature v. Nurture (Heritability) • Types of Studies –Twin Studies –Linkage Studies –Association Studies • Difficulties with Behavioral Genetics
  5. 5. Outline • Nature v. Nurture (Heritability) • Types of Studies –Twin Studies –Linkage Studies –Association Studies • Difficulties with Behavioral Genetics
  6. 6. Pamela Burford & Patricia Ryan • Identical twins (1954): – from same fertilized egg that split in early development; share identical DNA. • Similarities are striking – Physically similar: hair, eyes, height, looks, etc. – Both like to sew, art, cooking, same type of friends – Married two months apart, each has two children – Started new careers at same time: romance novelists 6
  7. 7. What Accounts for these Similarities? NATURE: Twins share identical DNA or NURTURE: Twins share similar environment, i.e., raised at same time and place by same parents 7
  8. 8. Okay, but… Doesn’t it make sense to think that genes play a greater or lesser role in determining specific behavior? This is what behavioral genetics is interested in…the genetic influence on complex traits, also known as heritability. And, not just in individual pairings of twins, but whole populations…
  9. 9. Heritability • Heritability is measured by looking at variation within a group. • Heritability is a number between 1 and 0. –H=1 means that all of the variation in a population is due to genetic factors –H=0 means that all of the variation is due to the environment
  10. 10. Heritability http://www.mvskokefood.org/cornstalk.JPG
  11. 11. Heritability Lets look at some corn plants http://www.mvskokefood.org/cornstalk.JPG
  12. 12. Heritability In the field, some are Lets look at some corn plants tall, and some are short http://www.mvskokefood.org/cornstalk.JPG
  13. 13. Heritability In the field, some are Lets look at some corn plants tall, and some are short Variability could be due to genes or environment http://www.mvskokefood.org/cornstalk.JPG
  14. 14. Heritability Let’s grow a clone of one corn plant in the same field http://www.mvskokefood.org/cornstalk.JPG
  15. 15. Heritability Let’s grow a clone of one corn plant in the same field What will happen? http://www.mvskokefood.org/cornstalk.JPG
  16. 16. Heritability Let’s grow a clone of one corn plant in the same field If they have the same variation, the original variation was due to environment http://www.mvskokefood.org/cornstalk.JPG
  17. 17. Heritability Let’s grow a clone of one corn plant in the same field http://www.mvskokefood.org/cornstalk.JPG
  18. 18. Heritability Let’s grow a clone of one corn plant in the same field If they have no variation, the original variation was genetic http://www.mvskokefood.org/cornstalk.JPG
  19. 19. Heritability Let’s grow a clone of one corn plant in the same field http://www.mvskokefood.org/cornstalk.JPG
  20. 20. Heritability Let’s grow a clone of one corn plant in the same field If they have 50% as much variation, the original variation was 50% genetic http://www.mvskokefood.org/cornstalk.JPG
  21. 21. Heritability Let’s grow a batch of the original seeds in a greenhouse http://www.mvskokefood.org/cornstalk.JPG
  22. 22. Heritability Let’s grow a batch of the original seeds in a greenhouse What will happen? http://www.mvskokefood.org/cornstalk.JPG
  23. 23. Heritability Let’s grow a batch of the original seeds in a greenhouse If they have the same variation, the original variation was due to genes http://www.mvskokefood.org/cornstalk.JPG
  24. 24. Heritability Let’s grow a batch of the original seeds in a greenhouse http://www.mvskokefood.org/cornstalk.JPG
  25. 25. Heritability Let’s grow a batch of the original seeds in a greenhouse If they have no variation, the original variation was due to environment http://www.mvskokefood.org/cornstalk.JPG
  26. 26. Heritability Let’s grow a batch of the original seeds in a greenhouse http://www.mvskokefood.org/cornstalk.JPG
  27. 27. Heritability Let’s grow a batch of the original seeds in a greenhouse If they have 50% as much variation, the original variation was 50% environment http://www.mvskokefood.org/cornstalk.JPG
  28. 28. Heritability Variation due to genes H= Variation due to genes + environment
  29. 29. Heritability Variation due to genes H= Variation due to genes + environment • Heritability is a measure of variation of a phenotype in a particular population in a particular environment.
  30. 30. Heritability Variation due to genes H= Variation due to genes + environment • Heritability is a measure of variation of a phenotype in a particular population in a particular environment. • For example: In a given population, for height, if H = 0.9, then 90% of the variation in height in that population can be explained by genetic variation.
  31. 31. Heritability Variation due to genes H= Variation due to genes + environment • Heritability is a measure of variation of a phenotype in a particular population in a particular environment. • For example: In a given population, for height, if H = 0.9, then 90% of the variation in height in that population can be explained by genetic variation. • If the environment or genetics changes so that it contributes more or less variation, heritability will change
  32. 32. Heritability • Heritability of: –economic risk attitude: 57% –hedonic capacity: 46% –stress perception: 44% –alcohol misuse: 30-36% –impaired balance in older people: 27% –anorexia nervosa diagnosis: 22% Twin Res Hum Genet. 2009 Feb;12(1):103-7. Osteoporos Int. 2008 Sep 19. Psychol Med. 2009 Feb;39(2):211-8. Epub 2008 May 28 Psychol Med. 2009 Mar;39(3):463-73. Am J Drug Alcohol Abuse. 2002;28(3):557-84.
  33. 33. Outline • Nature v. Nurture (Heritability) • Types of Studies –Twin Studies –Linkage Studies –Association Studies • Difficulties with Behavioral Genetics
  34. 34. Outline • Nature v. Nurture (Heritability) • Types of Studies –Twin Studies –Linkage Studies –Association Studies • Difficulties with Behavioral Genetics
  35. 35. Outline • Nature v. Nurture (Heritability) • Types of Studies –Twin Studies –Linkage Studies –Association Studies • Difficulties with Behavioral Genetics
  36. 36. Strategy of Twin Studies • Compares similarities and differences within a population; and between sub-groups within that population, e.g., MT, FT, and adopted individuals. • Insofar as twins are more similar than the rest of the population with regard to a specified trait, then that difference between the twins and the rest of the population is explained by genetic elements.
  37. 37. Two Assumptions 1. Genetic Similarity: Identical twins (MT) are 100% genetically identical and fraternal twins (FT) are on average only 50% genetically similar. (Caution: Not so clear that environment is similar between twins.) 2. Similar Environment: Environmental conditions for MTs raised in the same home are as similar as they are for FTs raised in the same home. (Caution: Even if raised apart, similar appearance results in similar treatment.) So: If the environmental conditions for identical twins (MT) are as similar as they are for fraternal twins (FT), …then behavioral geneticists infer that a closer average correlation (similarity) of traits for identical twins is due to the genetic influence on those traits. 23
  38. 38. Minnesota Twin Studies, 1988 24
  39. 39. Minnesota Twin Studies, 1988 • Thomas Bouchard – Minnesota Study of Twins Reared Apart – 100s of twins separated at birth, raised apart – Inventoried similarities & differences in batteries of tests. • Surprising similarities discovered at reunion – Oskar Stohr & Jack Yufe • Stohr raised in Germany as Catholic; Yufe raised in Trinidad as Jew • Same type of clothes, glasses, identical mustache, both liked practical jokes in elevators – Jim Lewis & Jim Springer • Same height and weight, dog named ‘Toy’ • Both married twice: 1st wife ‘Linda’, 2nd ‘Betty’ • Named son ‘James Alan’ and ‘James Allen’ – Mark Newman & Gerald Levey • Same type of mustache, glasses, each wore belt key on right side, and both volunteer firemen in New Jersey. 24
  40. 40. Minnesota Twins’ Personality • Bouchard found that a host of personality traits were substantially affected by genes; • > 50% (H = >.5) of variability observed in variety of traits (e.g., tendency to be religious) was typically explained by underlying variation in genes; • Concluded that upbringing had surprisingly little effect upon personality traits… Bouchard, T. (1990) Sources of human psychological differences: The Minnesota study of twins reared apart. Science 250; 223-28; see also Bouchard, T. (1994). Genes, environment, and 25 personality. Science 264; 1700-1701.
  41. 41. What DO Twin Studies Tell Us? • That behaviors (phenotypes) are a combination of both genetic and environmental influences. – That some phenotypes have a stronger or weaker genetic influence (as calculated by H). • Remember: heritability applies to a specific behavioral phenotype relative to a time, place, and environment – Change environment, different outcome. 26
  42. 42. What DON’T Twin studies tell us? 27
  43. 43. What DON’T Twin studies tell us? • NOT whether behavior is alterable – That is, whether genes are destiny. 27
  44. 44. What DON’T Twin studies tell us? • NOT whether behavior is alterable – That is, whether genes are destiny. • NOT which gene(s) responsible – That is, no gene(s) identified. 27
  45. 45. What DON’T Twin studies tell us? • NOT whether behavior is alterable – That is, whether genes are destiny. • NOT which gene(s) responsible – That is, no gene(s) identified. • NOT how the gene(s) affects behavior – That is, no causal pathway identified. 27
  46. 46. Outline • Nature v. Nurture (Heritability) • Types of Studies –Twin Studies –Linkage Studies –Association Studies • Difficulties with Behavioral Genetics
  47. 47. Outline • Nature v. Nurture (Heritability) • Types of Studies –Twin Studies –Linkage Studies –Association Studies • Difficulties with Behavioral Genetics
  48. 48. Linkage Studies • Looks for inheritance patterns of target behavior (phenotype) in a population (e.g., family tree) and then examines genetic similarities and differences within that population. – Looks for genetic similarities between those with similar target behavior; and – Looks for genetic differences between those with target behavior and those without target behavior. – Specifically looks for genetic markers associated with target behavior. (Classic Linkage Studies) 30
  49. 49. We need family trees to locate genes http://www.ucl.ac.uk/~ucbhjow/b241/mendel_1.html
  50. 50. We need known DNA differences • Remember there are several million common differences in the human population. • We can track how those markers are inherited in a family.
  51. 51. Tracking a phenotype in a family 11 11 Marker 1
  52. 52. Tracking a phenotype in a family 11 11 Marker 1
  53. 53. Tracking a phenotype in a family 11 11 1 1 1 1 1 1 Marker 1
  54. 54. Tracking a phenotype in a family 11 11 11 11 11 11 11 1 1 Marker 1
  55. 55. Tracking a phenotype in a family 11 11 11 1 1 11 11 11 11 11 11 11 1 1 11 Marker 1
  56. 56. Tracking a phenotype in a family 11 11 11 1 1 11 11 11 11 11 11 11 1 1 11 Marker 1
  57. 57. Tracking a phenotype in a family 11 11 11 1 1 11 11 11 11 11 11 11 1 1 11 1 Marker 1
  58. 58. Tracking a phenotype in a family 11 11 11 1 1 11 11 11 11 11 11 11 1 1 11 11 Marker 1
  59. 59. Tracking a phenotype in a family 11 11 11 1 1 11 11 11 11 11 11 11 1 1 11 11 1 1 1 Marker 1
  60. 60. Tracking a phenotype in a family 11 11 11 1 1 11 11 11 11 11 11 11 1 1 11 11 11 11 11 Marker 1
  61. 61. Tracking a phenotype in a family 11 11 11 1 1 11 11 11 11 11 11 11 1 1 11 11 11 11 11 11 11 11 11 11 11 11 11 Marker 1
  62. 62. Tracking a phenotype in a family 11 11 11 1 1 11 11 11 11 11 11 11 1 1 11 11 11 11 11 11 11 11 11 11 11 11 11 Marker 1 unlinked m 1 m m 1 1 m 1
  63. 63. Tracking a phenotype in a family 22 22 Marker 2
  64. 64. Tracking a phenotype in a family 22 22 Marker 2
  65. 65. Tracking a phenotype in a family 22 22 2 2 2 2 2 2 Marker 2
  66. 66. Tracking a phenotype in a family 22 22 22 22 22 22 22 22 Marker 2
  67. 67. Tracking a phenotype in a family 22 22 22 22 22 22 22 22 22 22 22 22 22 Marker 2
  68. 68. Tracking a phenotype in a family 22 22 22 22 22 22 22 22 22 22 22 22 22 Marker 2
  69. 69. Tracking a phenotype in a family 22 22 22 22 22 22 22 22 22 22 22 22 22 2 Marker 2
  70. 70. Tracking a phenotype in a family 22 22 22 22 22 22 22 22 22 22 22 22 22 22 Marker 2
  71. 71. Tracking a phenotype in a family 22 22 22 22 22 22 22 22 22 22 22 22 22 22 2 2 2 Marker 2
  72. 72. Tracking a phenotype in a family 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 Marker 2
  73. 73. Tracking a phenotype in a family 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 Marker 2
  74. 74. Tracking a phenotype in a family 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 22 Marker 2 linked m 2 m m m 2 2 2
  75. 75. Linkage and Sexual Preference • Genes determine sex (XX or XY). Do they determine sexual preference? In the 1990s Dean Hamer investigated the genetic basis for homosexual behavior. • Advertised in gay publications for people to participate in a study. Collected information from over 100 families. Asked participants if they had gay siblings or cousins, aunts, uncles, or grandparents. Concluded homosexuality ran in many of these families. Dean Hamer, 1995 • Discovered patterns in the distribution of gay relatives – most of the gay relatives were on the mother’s side of the family. 35
  76. 76. Genes and Sexual Preference • Hamer reasoned that if homosexual behavior has a strong genetic basis, then it would be passed on the X chromosome. But not sure where…so, performed linkage study. • Looked at 22 loci; a total of 40 pairs of brothers. • He concentrated on families with brothers that were both gay, and excluded families that had gays on the father’s side of the family (X linkage). 36
  77. 77. Xq28 Found Marker on X Chromosome (Xq28): – Of the 40 pairs, 33 had five markers that were the same. – Concluded that a gene or genes that might influence sexual preference might be near these markers – classic linkage inference. – July 1993, Science: Hamer et al., “A linkage between DNA markers on the X chromosome and male sexual orientation.” 37
  78. 78. “Gay Gene” Study received much attention*, both pro and con. – Newspapers reported on discovery of “Gay Gene” – 1995 study of 200 families with gay brothers (G. Ebers and G. Rice) found gay relatives on maternal side, but didn’t yield same result as Hamer (1993) – no linkage at Xq28. Hamer responded, in his book Living with Our Genes, that the Ebers and Rice study was conducted differently (and with bias), so their findings don’t dispute his own. – Controversy continues…research continues… *Published near the time that LeVay published on hypothalamic differences between homo- and 38 heterosexual men. See Debate posted online.
  79. 79. What does Hamer’s study tell us? • Not really a “gene” but a region of a chromosome. • No identified causal pathway from gene(s) to behavior • Complex behavior is, well, …complex – What is “homosexuality”? (time, place, environment) – Self-report and second-hand reports in study – Sexual behavior involves more than sex (See The Real Story on Gay Genes) 39
  80. 80. Outline • Nature v. Nurture (Heritability) • Types of Studies –Twin Studies –Linkage Studies –Association Studies • Difficulties with Behavioral Genetics
  81. 81. Outline • Nature v. Nurture (Heritability) • Types of Studies –Twin Studies –Linkage Studies –Association Studies • Difficulties with Behavioral Genetics
  82. 82. Association Studies (with Animals) • Basic Strategy: Find gene of interest, and manipulate it to determine effect on behavior phenotype. – Use knock-out (and -in) technology or selective breeding to produce lines of organisms with and without gene of interest; – Then, observe behavioral differences. 42
  83. 83. Romantic Voles • Science 10 June 2005. Study on variations in a gene promoter sequence that predict social behavior in voles – in particular parental care and monogamous mating. See also Nicholas Wade, A Gene for romance? So it seems (Ask the vole). New York Times, July 19, 2005 43
  84. 84. Romantic Voles • Differences in promoter sequences in a particular gene drastically affects complex social behaviors. • The difference in sequence length directly affects how, when and where the protein receptor for the hormone vasopressin presents itself in the brain – that is, it effects gene expression. • Key: Vasopressin is linked to social learning. 44
  85. 85. Romantic Voles • Researchers transferred a single gene from male prairie voles (which are monogamous) to male meadow voles (which are promiscuous). • The result was a monogamous meadow vole! 45
  86. 86. Romantic Mechanism? • Mating releases dopamine in the brain, dopamine receptors are located in the brain’s pleasure center. • In prairie voles (monogamous) the vasopressin receptors (social learning) are also located in the same pleasure centers. In meadow voles (promiscuous), the vasopressin receptors are not located in the same brain regions. • Explanation: when mating prairie voles learn to associate the pleasure with a particular female, meadow voles do not. Thus pair-bonds are formed in prairie voles and not meadow voles. 46
  87. 87. Same genes are in operation in humans and other mammals 47
  88. 88. Same genes are in operation in humans and other mammals 48
  89. 89. Same genes are in operation in humans and other mammals 48
  90. 90. Same genes are in operation in humans and other mammals RS3 • September 2008, Walum et al. • Not the same repeat as in prairie voles, but there are variations in the promoter region that are different between people (RS3) 48
  91. 91. Vasopressin in Humans • People were characterized on a Partner Bonding Scale to determine how happy their marriages were. solitary alleles 0 1 2 bonding score 48 46 45
  92. 92. Vasopressin in Humans Threatened divorce in the last year solitary alleles 0 1 2 No 85% 84% 66% Yes 15% 16% 34% Married? solitary alleles 0 1 2 Cohabitating 17% 16% 32% Married 83% 84% 68%
  93. 93. Love and Fos-B In early 1995, an M.D-Ph.D student, Jennifer Brown, was breeding mice with an inactivated form of the gene FosB. With the inactivation of the gene, healthy pups from the mutated mice died quickly. Observing this occurrence, Brown found that the mother mice ignored her offspring. From this discovery, Brown proposed that the inactivation of the gene FosB causes a defect in the nurturing behaviors of female mice. To prove this, Brown bred a series of knockout mice with the inactivated FosB gene. She then observed the nurturing behaviors of the knockout mice and compared them to those of the normal mice. 51
  94. 94. Fos-B and nurturing behavior Twenty-four to forty-eight hours after delivery, the mortality rate of the pups was in excess of fifty percent. After birth, it was immediately noted that mutant mothers failed to exhibit normal nurturing behavior: creating a nest, cleaning the pups, retrieving them to the nest, and crouching over them for warmth and nursing. The mutant mothers, rather, sat in a corner and ignored the pups that were scattered around the cage 52
  95. 95. With and without Fos-B Images: http://www.med.harvard.edu/publications/On_The_Brain/Volume06/Number2/synaphshot.html Summary of this research available at http://student.biology.arizona.edu/ honors96/group3/default.html 53
  96. 96. Outline • Nature v. Nurture (Heritability) • Types of Studies –Twin Studies –Linkage Studies –Association Studies • Difficulties with Behavioral Genetics
  97. 97. Outline • Nature v. Nurture (Heritability) • Types of Studies –Twin Studies –Linkage Studies –Association Studies • Difficulties with Behavioral Genetics
  98. 98. So, what about sexuality? • Sexual behavior is complex –We looked at several sexual behaviors: sexual orientation, mating patterns, and nurturing of young. –What is sexuality? What is the normal range of behavior? • Defining a behavior can be very difficult 56
  99. 99. Single genes generally have small effects 0 Functional 0 Functional In African-American and African-Caribbean populations there is a mixture of African and 1 Functional 1 Functional European forms. On average, people with the 2 Functional functional form have darker 2 Functional skin, but there are other genes involved. Darker skin http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16357253
  100. 100. Many genes affect multiple phenotypes Carried out a genome-wide association scan for variants associated with hair and eye pigmentation, skin Sulem P et. al Nat Genet. Dec. 2007 sensitivity to sun and freckling among 2,986 Icelanders.
  101. 101. What about sex? • Causal pathway is crucial –How do we get from gene to behavior? ? Gene Behavior 59
  102. 102. What about sex? • Causal pathway is crucial –How do we get from gene to behavior? ? Gene mRNA Protein Behavior 60
  103. 103. What about sex? • Causal pathway is crucial –How do we get from gene to behavior? Environment Gene mRNA Protein Behavior 61
  104. 104. Implications: Why study homosexuality? • Curiosity about genetics of sexuality • Evolutionary puzzle – If homosexuals defeat reproductive aims, why still present in population? • More problematic reasons… “medicalization” and politics 62
  105. 105. “Medicalization” of Behavior? When normal behavior is increasingly viewed as a disorder. Due to increasing commercial and social pressures to use medical interventions, what was once within a normal range is now considered dysfunctional, or abnormal – leading to reduced tolerance of different behaviors. – Consider Viagra and Prozac – Consider ADD/H and depression 63
  106. 106. “Leave gay sheep alone.” • Researchers in Oregon propose studies on sheep regarding sexual partner selection, hormones and brain function. • Responding on behalf of PETA to sex research in sheep, Martina Navratilova writes a letter to the universities in Oregon: •Sexual partner preference, hypothalamic morphology and aromatase in rams.Roselli CE, Larkin K, Schrunk JM, Stormshak F. Physiol Behav. 2004 Nov 15;83(2):233-45 •Brokeback Mutton: Gay sheep and human destiny.By William Saletan. http://www.slate.com/id/2158877/ Also see See: http://www.slate.com/id/2159262/ •Blog.bioethics.net/2007/01/martina-navratilova-leave-gay-sheep.html 64
  107. 107. “Leave gay sheep alone.” “How can it be that, in the year 2006, a major university would host such homophobic and cruel experiments? … I respectfully ask that you pull the plug on this appalling and misguided research. Surely you can find a way to redirect the millions of public tax dollars that are being wasted on these experiments to a more fruitful venture – perhaps by funding a gay and lesbian community center to foster dialogue and acceptance for people of all sexual preferences?” She also accused researchers of trying to find a “prenatal treatment for various sexual conditions.” 65
  108. 108. 4 Difficulties with Behavioral Genetics 1. Defining and measuring behavior 2. No (single) “gene for X”: – polygenetic influence 3. Predicting how behavior develops: – complexity of gene-environment interactions (nature/nurture) – pathways (effects of single gene are minimal) 4. Potential for misinterpretation and misapplication – “Medicalization” and politicization of normal behaviors 66
  109. 109. Summary • Tools of the Trade – Twin, linkage, and association studies – Heritability Estimates (nature v. nurture) – Genes and causal pathways • Specific studies – Minnesota, Hamer, voles, and mice – Types of inferences and limits of inference • 4 Difficulties of Behavioral Genetics
  110. 110. 68
  111. 111. Charles Darwin Film Series Evolution: Darwin’s Dangerous Idea Facilitator: Dr. Anya Plutynski Join the Marriott Library in celebrating Darwin’s 200th birthday with the film Evolution : Darwin’s Dangerous Idea. Evolutionary theory is featured in this film through the key moments in Darwin’s life and current research utilizing dramatization and documentary sequences. Dr. Anya Plutynski of the University of Utah’s Phi- losophy Department will introduce the film and be available for questions and answers. Her research Images from en.wikipedia.org specialization is in the history and philosophy of sci- ence, particularly evolutionary biology in the early 20th century. Date: March 4, 2009 Time: 1:00 p.m.—3:00 p.m. Place: Room 1120 Marriott Library Check http://darwin2009.utah.edu for more University of Utah and Marriott Library events. J. Willard Marriott Library Phone: 801-581-7533 University of Utah 801-585-7870 295 S. 1500 W. Salt Lake City, UT. 84112-0860 E-mail: robin.reid@utah.edu marie.paiva@utah.edu Organization
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