Flashcards in Lecture 13: Human and animal Deck (22):
What is behaviour genetics and what are its goals?
It's the study of genetic influences on behavioural qualities like personality dispositions, psychological abnormalities, cognitive and emotional processes.
It aims to determine the percentage of individual differences that can be attributed to genetics and environment. It wants to determine how these two interact and correlate with each other and it wants to figure out where the environmental effects are taking place.
Where are they?
What is DNA's purpose
Units of heredity that maintain their structural identity through generations. They are made up deoxyribonucleic acid.
They are aligned along chromosomes are part of them, chromosomes come in pairs.
DNA codes for ribonucleic acid which synthesises proteins.
What is RNA?
What do proteins do?
It's a single stranded chemical that serves as a model for the synthesis of a protein.
They determine the development of a body, they form part of the structure of a body and they act as enzymes to regulate chemical reactions (biological catalysts)
Describe Mendel's experiments
He used sweet peas for his experiment, they're easy to grow, cheap, rapid generation times, lots of offspring and the traits they had were easy to follow. He crossed a homozygous dominant trait with a homozygous recessive trait and the F1 generation was Yy and the dominant gene was expressed.
Define dominant gene
Define recessive gene
Different version of the same gene that produce a characteristic
When someone has an identical pair of genes on the two chromosomes
When someone has an unmatched pair of genes on the two chromosomes
A gene that shows a strong effect, it can be homo or heterozygous; DD, Dd, dD
The effect of this gene is only shown when homozygous; dd.
Describe how some disorders you can be a carrier of
Some disorders are recessive so if you have a heterozygous dominant gene Dd then you would be a carrier as you have only inherited one of the recessive genes. This happens with Phenylketonuria
Can categorical genes cause continuous traits?
Yes because the gene gives them the predisposition and the environment decides how much the gene is expressed.
Describe the two types of genes
Autosomal genes cover all genes bar sex linked ones
Sex linked genes are located on sex chromosomes, in mammals, the females have two X chromosomes and the males have XY.
How many proteins are on each type of sex chromosome?
What does this mean?
27 proteins on a Y chromosome and 1500 on an X chromosome.
This means that sex linked genes are usually referred to as X linked genes (males are more likely to have sex linked diseases as it only needs to be present on one of their chromosomes. If a gene is present in both sexes but is more prevalent in one particular sex, then they are called sex limited genes.
What happens during reproduction in terms of X and Y chromosomes?
Females always contribute an X chromosome whereas males can contribute an X or a Y. X=female, Y=male.
Briefly describe the genetics of behaviour
They don't directly produce behaviours but they produce proteins that increase the probability of the behaviour being expressed and developing. Genes can also alter your environment by causing a behaviour which alters how people perceive and react to you, this is an indirect effect.
List some examples of how selection has modified behaviour
Over many generations it can cause wild foxes to be tame and domesticated and it can cause stray dogs to become less tame and more wild, this is reverse domestication.
Describe gene knockout
It's when a gene is made inactive to see what effect it has on the organism. For example, if leptin is knocked out then it causes an uncontrolled appetite which usually leads to obesity, this is found in rats. A gene can also be knocked out in rats to cause aggression.
Describe human gene hunting
This was inspired by animals and it's an idea that could be used to prevent certain behaviours, this could be done via knockout. For example, vasopressin influences fidelity. Using this technique, we could reduce alcoholism, depression, anxiety etc. However, animal models may not translate well to humans.
Give an example study about temperament and genetics
Give another example
Suomi's study. This was done on monkeys, it was found that there were two alleles of one gene, one was short and the other long. The short version causes neurobehavioural deficits only if the infant monkey was raised without the mother and was raised by peers. The long version didn't cause this, no matter the rearing technique. This shows that with the short gene, there is maternal buffering.
The study by Caspi et al 2003, this found that transporter locus interactions can affect people's likelihood of developing depression. If they had 2 short alleles then they were twice as likely as people with 2 long alleles to develop depression after 4+ traumatic events.
List the four types of behavioural genetics methods and list an advantage and disadvantage of each
1. Selective breeding (not with humans), + you can infer heritability, - it's unethical on humans
2. Family studies, + provides heritability estimates, - you violate equal environment assumptions
3. Twin studies, + Heritability and environmental estimates, - violates equal environment assumptions and representativeness assumptions
4. Adoption studies, + Heritability and environment estimates, without violation of equal environment assumptions, - Not representative and selective placement problems.
What is heritability?
The proportion of observed variance in a group of individuals that can be explained by genetic variance. Aka, the proportion of phenotypic variance that can be explained by genotypic variance. If the heritability is 20, then the environment has 80% influence.
Discuss general findings of adoption studies
Adoptees are more like their biological parents in comparison to their adopted parents in terms of personality, intelligence and temperament. Adopted siblings are no more alike in personality than randomly selected people and their personalities are largely unrelated to their adoptive parents. Does this mean there are genes for personalities?
What is the difference between identical (Mz) twins and fraternal (Dz) twins?
Identical twins share all their genes (genetically identical) because the sperm fertilises the egg and then the egg split in two within the first two weeks. They have identical genomes and if a trait is present in both then it probably has a genetic influence. If they are raised in different environments, then all the traits that are different have an environmental influence.
Fraternal twins share half of the genes (same as normal siblings) because there are two separate eggs that are fertilised by separate sperm.
List examples of concordance
How often a trait occurs in both members of a pair of twins, it helps establish whether the trait has a genetic basis.
Alcoholism has 55% concordance
Cystic fibrosis has 100% concordance
Schizophrenia varies between 48 and 69%
The highest level of concordance out of the 5 personality traits was openness with about 60%, closely followed by extraversion
General academic ability has 86% concordance
List the disadvantages of twin and adoption studies
They have a shared early and foetal environment
Adoption isn't random
Mz twins have a closer foetal environment than Dz, this is an environmental influence