Lecture 4: Behavioral Genetics Flashcards
What is genotype?
actual genetic makeup of an individual.
What is phenotype?
observable expression of genes in this case referring to behavior.
What do phenotypes result from?
Phenotype (behavior) presumably results from interaction between genotype and environment.
What is pleiotropy?
multiple effects of a single gene which may affect behavior ex) albinism in mice
What is polygenic trait?
many genes controlling a particular phenotype, such as behavior; most behaviors are probably polygenic
What are the problems with hybridization
For example a cross between a horse and a donkey= a mule. Hybrids are often sterile; behavioral differences often involve several genes.
What are 3 methods of hybridization?
- cross two closely related species that have species specific behavioral differences, 2. observe behavior of hybrids with parental species, 3. backcross the hybrids with parental species
When bees from hygienic and non hygienic colonies were crossed what happened?
All of the F1 bees were non hygienic suggesting that recessive genes control hygienic behavior.
What happened when hybrids were backcrossed to the hygienic strain?
25% were hygienic, 25% uncapped cells but did not remove dead pupae, 25% removed dead pupae if already uncapped, 25% were non hygienic
How many genes control hygienic behavior?
2
What happens if animals are inbred rigorously?
All the original variation will ultimately be eliminated.
What happened with fruit flies F2 generations when hybrids were crossed with each other?
F2 generation had rover:sitter ration of 3:1 (monohybrid cross)
How many genes controlled rover and sitter behavior?
one gene: rovers= RR and Rr and sitters= rr
What happens when slow and fast learning mice are bred selectively in separate groups?
offspring of fast learners are fast learners and offspring of slow learners are slow learners.
Degrees of relatedness for first degree relatives? second degree relatives? third degree relatives?
Parent offspring= 0.5
full siblings= 0.5
Degrees of relatedness for first degree relatives? second degree relatives? third degree relatives?
Parent offspring= 0.5
full siblings= 0.5 --------- half siblings= 0.25 grandparent-grandchild= 0/25 uncle/aunt-niece/nephew= 0.25 ----------------- first cousins= 0.125
What are monozygotic twins? How genetically similar are they?
100% genetically similar
What are dizygotic twins?
50% similar genetically
Do identical or fraternal twins have more similar environments?
When questioned, 40% of twins were mistaken about whether they were identical or fraternal
How is heritability estimated?
Falconer’s formula: doubling difference between correlations for MZ and DZ twins.
What is the Binet test for intelligence?
developed by Alfred Binet and measures intelligence
What are the 4 main criticisms of IQ testing?
- intelligence too complicated to be defined by a single measurement.
- IQ tests biased by language, educational level and culture
- IQ rests often lead to racial and cultural discrimination
- cross correlations occurred among the different tests, meaning that a person who scored well on one test score similarly well in others
What causes PKU?
a single recessive gene in PAH gene on chromosome 12.
-Retardation caused by absence or inactivity of enzyme phenylalanine hydroxylase, which converts phenylalinine to tyrosine.
How is PKU treated?
a special diet that is low in phenylalamine
What happens to PKU heterozygotes?
less able to convert phenylalamine to tyrosine than normal dominant homozygotes; thus have a lower IQ than normal.
Why is the gene that affects Huntington’s disease maintained in the population?
Symptoms do not begin until after child bearing years.
How are males and females affected by major depressive disorder?
1.5-2 times more females than males, but imbalance decreases with age
How are some males and females affected by bipolar disease?
They are equally affected.
How are males and females affected by somatization disorders?
3-10 times more common in women than in men.
Do humans have spiritual genes?
No, little evidence for heritability.
What is the God gene hypothesis?
Humans with VMAT2 gene are predisposed to episodes interrupted by some as religious revelation.
True or False: Humans are predestined by genetics and not predisposed.
False: we are predisposed.
