inheritance continued Flashcards
define heritability
the proportion of variation in a trait due to genetic differences among individuals
how can heritability be estimated
1) comparing parents and offspring
2) twin studies
3) pedigrees
what is Galton’s rule
regression towards the mean- he concluded that children of tall parents are taller than the average population but shorter than their parents on average
children from shorter parents have offspring which on average are taller than their parents but shorter than the average population
what does Galton’s data indicate
that 60% of the variation in height is due to genetic variation and 40% due to environmental variation
what is the difference between monozygotic and dizygotic twins
M = genetically identical and usually share a similar environment
D= genetically non-identical and usually share a similar environment
define concordance
the proportion of cases in which both members of a pair of twins show a trait (out of the cases where at least on twin shows that trait)
what is a pedigree
a graph which can show pathways of genetic inheritance and measurements of a trait of all individuals
what doesn’t heritability tell us
to what extent genes impact a trait in one individual
for example
more favourable environment more likely heritability of a tall gene will be expressed compared to worse conditions e.g. low nutrients- the plant will still have the ‘tall gene’ however enviro suppressed it, so cant tell by simply looking how much of a trait is from genes or from enviro
what can heritability give us a good idea of
how a population would respond to artificial selection= if a trait has high heritability it has a greater potential to respond to AS compared to low
what is cultural inheritance
refers to the storage and transmission of info by communication, imitation, teaching and learning e.g. experiment showing female fruit flies which witnesses a male marked with one of two colours mating later prefer to mate with similarly coloured males which is further copied imitating a tradition
or naked mole rats which adopt the same vocalisations as their adopted colonies
what could cultural inheritance account for
‘missing inheritance’- many GWA studies of human diseases don’t find sufficient genetic effects to explain heritability
what is cross fostering
Cross-fostering is transfer of young between mothers e.g.
In banded mongooses, natural cross fostering occurs
Young banded mongooses inherit their foraging niche from cultural role models, not parents
Cultural inheritance occurs in the first few months of life, but lasts a lifetime
define epigentics
the inheritance of variation beyond differences in DNA base sequence. Changes are inherited by descendent cells and maybe descendent individuals e.g. the enviro
what molecular processes lead to epigenetic changes
1) changes in patterns of DNA methylation
2) histone modifications
3) RNA molecules
how do changes in patterns of DNA methylation lead to epigenetic change
the addition of a CH4 (methyl) group to a nucleotide base (usually cytosine which is next to guanine) forming CpG islands
what is a CpG island
commonly found near transcription start sites
they inhibit transcription factors from binding to RNA polymerase cant be recruited
how can epigenetic changes affect queen bees
can be responsible for differences in phenotypes of bee workers and queens
eating royal jelly supresses Dnmt3 which normally methylates DNA leading to expression of genes which characterise a queen
how can histone modification lead to epigenetic change
modifications such as addition of phosphates, methyl groups and ubiquitin can occur at different amino acids which can increase or decrease transcription by modifying chromatin structure
what is paramutation
an interaction between two alleles that leads to a heritable change in the expression of one of the alleles (the DNA base sequence remains unchanged)
what is genomic imprinting
when some genes are expressed more if they are inherited from the father and others if they are inherited from the mother
what describes particular forms of heritable epigenetic changes
paramutation
genomic imprinting
