Need for an integrated view of development – genetic & environmental influences. For example – height ‘determined’ by genes – but diet & other environmental factors will have an influence. Evolutionary adaptations also influence development.
Different ‘levels’ of explanation available – e.g. tantrum throwing at a supermarket:
- Proximate – e.g. wrong cereal selected by mum
- Developmental – may have seen others throw tantrums and get what they want (experience)
- Genetic – may be predisposed to tantrums
- Comparative – happens across species
- Functional – selected through evolution as a way of securing parental attention
Potentially all equally valid explanations – and shows evolutionary and genetic explanations are complementary to more traditional psychological explanations of development.
Perspective: Genes contribute to the differences seen between individuals; shared environments contribute to similarities observed. Genetic effects play a key role in the development and expression of behaviour.
However – there is a complex relationship between genes and the environment – MZ twins are not completely identical (e.g. body tissues & cell components – Malcolm & Goodship); different genes can underlie identical developmental outcomes.
Epigenesis - the view that development occurs as a result of interaction between genes and the environment – challenges the view that genetics is completely deterministic of development.
Heredity – Mendel – able to determine scientific laws that predicted the traits in pea plants based on their parents. Proposed the existence of genes – units of inheritance.
Law of segregation – two copies of genes in each parent; offspring get one copy from each parent. The alternative form of each gene is known as an allele – may be dominant or recessive (only inherited if both copies of the gene are recessive.)
Phenotype – observable characteristics of an individual – e.g. eye colour.
Genotype – Complete set of genes in an individual, determined at conception.
Homozygous – two identical alleles for a specific gene
Heterozygous – two different alleles
e.g. Cystic fibrosis caused by an individual having homozygous alleles for the recessive gene; if not present in parents they are heterozygous carriers (a trait may re-emerge in this way in future generations.)
Law of independent assortment – inheritance of one gene not affected by another.
Organisation of genes – DNA molecules (A,G,C,T), in triplets assembled into chromosomes. Many sequences of DNA are junk; genes are the bits of the DNA sequence that have an identified purpose. Each gene occurs at a locus. Humans have 46 chromosomes; 23 pairs. 22 are matching; the 23rd determines sex (**=female, XY=male.) Red-green colour blindness is a recessive allele on the X chromosome – explains why men are more prone to this condition.
One complete set of 23 chromosomes inherited from each parent at conception – resulting in a novel combination of genes. Chromosomes = the human genome; mapped by 2003.
The Role of Genes – produce proteins – essential building blocks of the body. Involved in neurotransmitter…