Behavioural Genetics [W1] Flashcards
Def: Sexual Selection
mate choice based on
Who likened the mind to a Swiss army knife?
Cosmides & Tooby (1992)
What do Cosmides & Tooby mean re: mind is like a Swiss army knife?
made up of specialised modules designed to solve specific problems–not general learning device. Central idea to evolutionary psych
Def: genotype
set of genes an organism posesses
Def: phenotype
appearance of the organism
Def: alleles
pair of genes that control the same trait
identical pair of alleles is _________
homozygous
different alleles of same gene are __________
heterozygous
Def: heritability
the estimate of how much genes contribute to the variation in a phenotypic trait in a given population
Def: epigenetics (vis a vis behaviour)
the study of how environmental factors influence gene expression
Explain the rat study by Tryon (1934)
Rats in maze to test cognitive abilities. Interbred rats who made fewest mistakes over generations –> ‘bright group’ (few errors). Interbred rats who made most mistakes over generations –> ‘dull’ group (most mistakes). Less overlap through successive generations. Conclusion: some elements of intelligence are determined by genes. Intelligence is likely a polygenic trait bc several generations required for groups to separate.
Explain the study by Cooper and Zubeck (1958) re: rats in restricted environments
Raised rats in restricted, normal and enriched environments. ‘Dull’ rats raised in enriched environments improved. ‘Bright’ rats weren’t as good if raised in restricted environments. Conclusion: experience ‘overcomes’ genetic influence
According to Plomin and DeFries (1998) in studies of intelligence, correlations between identical (monozygotic) twins exceed those for fraternal (dizygotic) twins in_______, __________, _________, _________.
Verbal abilities, adulthood, spatial abilities, childhood
Def: polygenic trait
several genes involved
Explain rat study by Searle (1949)
Compared ‘bright’ and ‘dull’ rats on 30 behavioural tests. Conclusion: selective breeding affects multiple (not single) traits
def: monozygotic (twins)
identical; develop from sign egg that splits after being fertilised by single sperm ==> share 100% of genes
def: dizygotic (twins)
fraternal; develop from two separate eggs, fertilised by two separate sperm ==> share 50% of genes (same as any other siblings)
Plomin and DeFries (1998) twin studies (intelligence). Explain.
compared twins (MZ/DZ) on range of cognitive tasks; conclusion: strong evidence for genetic influence on variations in intelligence, that doesn’t decrease over. Twins raised in similar environments –> diff in scores more likely due to genes [high heritability]. Twins raised in very different environments ==> lower heritability score
Plomin and DeFries (1998) adoption studies (intelligence). Conclusion?
Evidence for strong genetic influence on variations in ‘intelligence’
What part of cell contains entire genome?
nucleus
def: dendrite
a branch that extends from the cell and receives information from other cells
def: dendritic spine
a protrusion on a dendrite that increases the SA of the dendrite
def: nucleus
structure w/in cell that contains genes and chromosomes
def: nuclear membrane
the membrane surrounding the nucleus; separates chromosomes from rest of cell; has small pores to allow nucleic acids and proteins to pass through
def: mitochondrion
organelle where respiration and energy production happen
def: endoplasmic reticulum
folded layers of membrane where proteins are assembled
def: intracellular fluid
fluid inside cell where all the cell’s structures are suspended
def: tubule
tiny tubes that help give the cell structure/shape and transport molecules
def: cell membrane
membrane surrounding cell
def: axon
extension from cell that transmits information from cell body to other cells
Nature or nurture? Explain
both. Genes influence behaviour but environment influences how genes are expressed –> see epigenetic. Genes can’t ‘behave’ on their own, must have an organism. Organisms built according to genetic plan, and how that plan functions depends on environment.
Who recognised the importance of evolution by natural selection?
Charles Darwin (1859)
What were Darwin’s 3 main views?
- Species are non-constant, they evolve.
- Evolution must be gradual.
- The prominent mechanism of evolution is natural selection.
What was implied by branching evolution?
Common ancestors
def: codons
start/stop points of genes along DNA
def: exons
useful sections of DNA; transcribed
def: introns
not transcribed
What regulates gene expression?
transcription factors
Who discovered the double helix structure of DNA?
Crick and Watson
Why is double helix shape important?
Allows for replication and protein synthesis. DNA unwinds and strands separate to allow copies of each strand to be made
def: nucleotide base pairs
2 chemical bases bonded together to form one ‘rung’ of the DNA ladder
What are the four bases? (DNA)
adenine (A), cytosine (C), guanine (G), or thymine (T)
Describe the process of DNA transcription
DNA is transcribed to a strand of messenger RNA, which travels out of the nucleus to ribosomes in the cell body where the information is translated to produce chains of amino acids. Amino acid chains build up into proteins.
When are genes transcribed?
when protein products are needed, i.e. at certain stages of development. Expression is regulated by transcription factors.
Gregor Mendel, discovery?
Laws of inheritance. Inheritance of specific traits in peas.
Explain Gregor Mendel’s pea experiments for genetic inheritance.
Peas were bread over generations to determine how traits were passed on. Traits were either present or absent between plants––> not in between.
What happens with heterozygous alleles?
One is expressed (dominant) and the other is not (recessive)
def: polymorphism
common forms of a different gene
def: wild type
common allele
def: mutations
less frequent, often determine genetic disorders
def: gene
inherited factor
def: knockout tech (KO)
when a gene is removed or inactivated so it is not expressed; useful to determine function of a gene, typically in mice or fruit flies
def: transgenic (animals)
gene is added to the genome and passed along/expressed in subsequent generations
def: cloning
implanting genome into unfertilised egg from which nucleus has been removed
Where is the damage in Huntington’s disease?
degeneration of neurons in caudate nucleus and putamen (striatum)
Symptoms of Huntington’s disease
chorea, cognitive deficits, psychicatric deficits; appears age 30-40
What is Huntington’s disease
hereditary disorder, autosomal dominant gene defect on chromosome 4
What is the chance of a child getting Huntington’s if one parent is a carrier?
50% Huntington’s, 50% normal
What is the chance of a child getting Huntington’s if both parents are carriers?
75% Huntington’s, 25% normal
Huntington’s: How many copies of mutant allele are required to exhibit the trait? Dominant/recessive?
1 copy needed; dominant trait
Tay-Sachs: How many copies of mutant allele are required to exhibit the trait? Dominant/recessive?
two copies of mutant allele needed; recessive trait
What is the chance of a child getting Tay-Sach’s if one parent is a carrier, w/ normal partner?
50% normal; 50% carrier; no disease
What is the chance of a child getting Tay-Sach’s if both parents are carriers?
25% Tay-Sachs; 50% carriers; 25% normal
Tay-Sach’s: if one parent has a mutant allele?
no symptoms (recessive gene) but is a carrier
What is trisomy 21?
Down’s syndrome – extra copy of chromosome 21
Is gene expression always the same? Explain. (Epigenetics)
External environment can influence gene expression (i.e., stress, drug abuse, etc.); Genes can be silenced if they’re blocked, by other molecules, from being transcribed. Can also be enhanced by molecules that encourage DNA to unfurl.
“gene off”
epigenetic marks that inhibit gene expression by causing the chromatin to fold tightly, preventing the gene from being read and expressed
“gene on”
epigenetic marks that encourage chromatin to unfurl, which help encourage transcription and spur gene activity
Are genes “for” specific behaviours? Explain.
No. A gene “for” a behaviour doesn’t explain how changes in the gene influence changes in behaviour. Environment contributes to genetic expression of the gene.
Name some complex behaviours with high heritability, shown via twin studies.
alcoholism, addition to drugs, ADD/ADHD, affective disorder, schizophrenia
