genetics and behaviour- lecture 2 Flashcards
early thoughts on genetics
acquired characteristics can be inherited
what did darwin say about genetics
characteristics inherited due to pangenesis
what is pangenesis
the body produces gemmules which travel to sex organs and pass on characteristics to further generations
BUT children arent an exact copy of parents- some features identifiable as coming from 1 parent but others appear to be a blend
who is gregor mendel
- an augustine monk
- carried out a series of experiments but only really acknowledged in 1900s
- discovered dichotomous traits and true breeding lines
- pea plant experiment
what are dichtonomous traits
traits that occur in one form or another not both e.g. pea plant seeds= brown or white
what are true breeding lines
pure interbreeding always produces the same trait e.g. brown seed plant= brown seeds
mendelian genetics
- certain factors are transmitted from parent to offspring- mendel suggested these were directly responsible for physical traits
key terms= genotype, phenotype, homozygous, heterozygous
use punnet square to understand simple genetic inheritance
genotype
genetic code
phenotype
the physical trait- affected by environment
homozygous
2 identical trait genes
heterozygous
2 different trait genes
mendels legacy
- genes- the factors that are passed on
2 genes for every dichotomous factor
organisms randomly inherit 1 gene from mother and father
combination determines genotype and phenotype for the trait
1 of genes can be dominant e.g. brown eyes= B, blue eyes= b
DNA structure
1 phosphate group, pentose sugar, nitrogenous base
adenine, thyamine, cytocine, guanine
genetic base pairing- A+T G+C
sequence of 3 bases- codon
each codon codes for 1 amino acid
completed code is the gene
gene is located on chromosomes
how many genes in nucleus
34000 housed in 46 chromosomes (23 pairs)- 1 from each pair
22/23 pairs are autosomal- determine all traits apart from sex
23rd pair determines phenotypic sex
why are males more suceptible to sex linked diseases than females
- females receive 2x chromosomes so they get 2 doses of sex linked genes, males only recieve 1 (comes from the mother)
- if female has harmful reccesive gene on 1 chromosome they usually have dominant normal gene to counteract it
- males more likely to recieve defect as only has 1 X
inheriting haemophelia
females often carry the gene
if males have this gene, it shows on the phenotype
genes to behaviour
genes dont supply every detail of an individual
they initiate particular developmental pattern that may/may not be activated depending on many possible environmental and physiological changes
what is heritability
the degree to which differences in characteristics are due to genetic differences
this takes a value between 0 and 1
the scientific study of heritability is called behavioural genetics
methods in behavioural genetics
- artificial selection
- family studies
artificial selection
tryon (1940) trained rats to find their way through a maze
he selectively bred the fastest and the slowest
over generations, 2 clear groups emerged
family studies
we can take specific family membersand compare their behaviours with people of differing genetic relations
if characteristics are more common in closely related individuals then it could have a genetic component
some studies have compared MZ twins with DZ twins, because MZ twins are genetically identical they should show greater similarities (concordance) in their behaviours than DZ
concordance in MZ twins
MZ twins show high concordance rates for many physical and behavioural characteristics
BUT
twins reared in same environment which can affect their behaviours
MZ raised apart should still be more similar than non identical raised together
BUT no behaviour has heritability 1 so genes and environment interact to form behaviours
