Wk3 Cognitive Genetics Flashcards
what do genes basically do?
code for a protein product
what could be the consequences of slight variation in protein expression?
alterations in brain function and structure between people
what is the basic idea/model of how cognitive genetics works?
genetic variation -> protein expression -> brain (structure/function) -> cognition
genes affect cognition through the above pathway
what is a genotype?
variation in genes across people
what is the aim of cognitive genetics?
linking genetic variation to variation in cognitive abilities
what are three ways to investigate genotypes?
twin studies
candidate genes
genome wide association
def complex trait. what influences it? 3
a quantifiable property of an organism
influenced by
- multiple genes
- enviornmental factors
- interactions between them
phenotype?
physical appearance of an organism with respect to a trait
how a complex trait manifests
endophenotype?
measurable components that lie along the causal pathway between disease (phenotype) and distal genotype
why examine an endophenotype?
can be hard to examine the full expression of a phenotype. e.g. complex clinical diagnoses are required for ADHD vs easier to look at sustained attention as an aspect of the full trait
what is an advantage to investigating an endophenotype? consequence?
simpler and easier to measure (than a complex trait) ,
so possibly controlled by fewer genes.
what makes up the genome?
23 pairs of chromosomes, in each pair one comes from each parent
what is a gene?
length of DNA that specifies a particular protein product
what is an allele?
one of two or more forms of a gene (different versions of the same gene)
what does homozygous mean?
the same alleles on both chromosomes (mother and father)
what does heterozygous mean?
different alleles (forms of the same gene) at each chromosome
if you got different alleles from your mother and father this gene is ___
heterozygous
what are two common types of genetic variation?
single nucleotide polymorphisms (SNP)
variable number of tandem repeats (VNTR)
what is a single nucleotide polymorphism?
when alleles differ at a single base pair (or one location)
if AAGCCTA differs from AAGCTTA, this is a ___
single nucleotide polymorphism
what is a VNTR?
a location in a genome where a short nucleotide is organised as a tandem repeat of a particular (variable length, 10 -100)
how are individuals classified using VNTR?
based on how many copies of the repeat length of interest they have: 0, 1, or 2.
what is a polymorphism?
the presence of two or more variants (alleles) in a gene or DNA sequence in a population
what are the most common polymorphisms?
SNPs
what does a SNP reflect?
a change in a single base in the DNA that differs from the usual base at that position
a polymorphism in the length of tandemly repeated short sequences of DNA is called ___
VNTR
2 phenotypical aspects of ADHD required for diagnosis
inattention
hyperactivity/impulsivity
what would be an endophenotype in ADHD?
sustained attention
def sustained attention
ability to maintain goal-directed focus in the absence of exogenous or external cues
what task can test sustained attention? how does it measure it?
SART: sustained attention to reaction time
behaviourally
what does a SART task involve?
press or don’t press a button, in response to a cue presented earlier
what is an advantage of heritability/twin studies?
they can measure both genetics and environment and compare their interaction
what is a disadvantage of heritability/twin studies?
they can’t specify which genes, only that genes are important
what are the 3 influences in a twin study model?
additive genetic influences
shared environmental influences
non-shared environmental influences
what could you conclude if MZ twins have low correlation on an ability/trait? why?
differences are due to non-shared environments
MZ twins share genes and environment
what could you conclude if there are high correlations of a trait/ability in both MZ and DZ twins? why?
effects are due to shared environment
differences in % of shared genes between DZ & MZ did not produce an influence
what could you conclude if there are high correlations in a trait/ability for MZ twins, but low correlations for DZ twins? Why?
effects are due to genetics
100% shared genes in MZ twins is the only extra factor that could account for increased twin similarity
heritability estimate for ADHD?
60-90%
describe the dose effect of genes on ADHD
unaffected siblings perform better on sustained attention but worse than healthy controls