week 3 - genetics and evolution Flashcards
behavioural genetics
Behavioral Genetics - The empirical science of how genes and environments combine to generate behavior.
how much genetic material do we share with fellow human/parents/siblings/twins/etc.
All humans share ∼99.5% of their genetic material
The remaining 0.5% of alleles vary across people
We share 50% of our genetic material with our parents and with our siblings
Twins share 100% percent of their genetic material - they are monozygotic, since they came from the same egg
Dizygotic twins come from two separate eggs and still share 50% of their dna
Grandparents and niblings (nieces/nephews) share 25% of their dna
Cousins share 12.5% of their dna
Siblings often share the same environment, but their genetic material is only 50% the same
quantitative genetics
Quantitative Genetics - Scientific and mathematical methods for inferring genetic and environmental processes based on the degree of genetic and environmental similarity among organisms. Studies with twins.
heritability coeficient
Heritability Coefficient - An easily misinterpreted statistical construct that purports to measure the role of genetics in the explanation of differences among individuals. Heritability is a measure of how much of the variation you see in a certain trait can be attributed to genetic variation. 0 = no genetic component
adoption study
Adoption study - A behavior genetic research method that involves comparison of adopted children to their adoptive and biological parents. Traits can be from your environment and your genes.
twin studies
Twin studies - A behavior genetic research method that involves comparison of the similarity of identical (monozygotic; MZ) and fraternal (dizygotic; DZ) twins. Only thing different is their behaviour and environment - proves that environment is just as crucial as genetics. “Jim twins” case is very rare.
phenotype
Phenotype: The pattern of expression of the genotype or the magnitude or extent to which it is observably expressed—an observable characteristic or trait of an organism, such as its morphology, development, biochemical or physiological properties, or behavior. Differences in genotype account for only 1-2% of the total risk for inheritance of personality traits and mental disorders? How can we explain the remaining heritability of these things?
phenotypic plasticity
Phenotypic plasticity - Phenotypic plasticity of a trait is variation of the target phenotype for a given genotype in different environments. In particular, a reaction norm characterizes plasticity by describing how the target phenotype for a specific genotype varies as a function of an environmental variable.
dna wraps around ____
DNA wraps around histones (group of 8 proteins) which together, make up nucleosomes, which are the repeating units of chromatin: A structural solution for maintaining/accessing the genome
There is an immense amount of genetic material in a cell
DNA wraps around histones very tightly - this combo is called a nucleosome and repeats throughout our cells
Nucleosomes are repeating units of chromatin
Chromatin - a structural solution for maintaining/accessing a genome
epigenetics
the study of changes brought about in gene expression by external of environmental influences.
Epigenetics: The study of heritable changes in gene expression or cellular phenotype caused by mechanisms other than changes in the underlying DNA sequence. Epigenetic marks include covalent DNA modifications and posttranslational histone modifications. Same sequence of dna but environmental factors can alter your dna.
dna methylation
The addition of a methyl group to DNA, typically on cystine.
DNA methylation: Covalent modifications of mammalian DNA occurring via the methylation of cytosine, typically in the context of the CpG dinucleotide.
Often happens when a methyl group get added to the dna molecule which adds the effect of the reduced gene without affecting the dna - blocks access to that dna
histone modifications
Histone modifications - Posttranslational modifications of the N- terminal “tails” of histone proteins that serve as a major mode of epigenetic regulation. These modifications include acetylation, phosphorylation, methylation, sumoylation, ubiquitination, and ADP- ribosylation.
Histone has a + charge and dna has a - charge
Takes away + charge on the histones, which removes the attraction and the nucleosome isn’t as tight
Allows for more transcription
epigenome
Epigenome -The genome-wide distribution of epigenetic marks, which can vary widely depending on cell type, tissues and brain regions. Influenced by a range of external environmental factors.
Can depend on environments that parents experienced
Tends to be from external environmental factors
epigenetics
Mothers exposed to stress/depression - leads to increased hormonal stress in their children
Epigenetics:
Can be influenced by childhood nutrition
Children born to mothers who experienced famine showed changes in DNA methylation.
Also regulate learning and memory
DNA methylation has been implicated in the maintenance of long- term memories, as has histone acetylation
Pharmacological manipulations that decrease acetylation and methylation impair memory.
Related to psychological disorders.
sexual selection
Sexual Selection - The evolution of characteristics because of the mating advantage they give organisms.
Inter-sexual competition - A process of sexual selection by which evolution (change) occurs as a consequences of the mate preferences of one sex exerting selection pressure on members of the opposite sex.
Intra-sexual competition - A process of sexual selection by which members of one sex compete with each other, and the victors gain preferential mating access to members of the opposite sex.
