lecture 6 - genetics and epigenetics Flashcards
who studied peas and proposed the idea of dominant traits?
Gregor Mendel
what did the study of meiosis reveal in 1905
sex is based on
chromosomes, thread-like structures inside the nucleus of animal
and plant cells
function of histones
allow long strand of DNA to be curled up and fit into chromosomes
genome
any organism’s complete set of DNA, including all its genes.
An organism’s genome contains all the information needed to build and maintain the organism
what allowed sequencing of DNA?
CRSPR
true or false; all cells in the body are genetically identical
true, but body has cells w diff forms and functions
how are changes to DNA sequences passed along
through generations
genotype
part of genetic makeup of an individual which determines their potential characteristics
homozygous
if alleles are the same
heterozygous
if alleles are different
phenotype
set of observable characteristics of an individual resulting from the interaction of the genotype with the environment
different alleles code for different _______
phenotypes
what are 3 examples of dominant phenotype traits
polydactyly (6 fingers) (dom over 5 fingers)
lobed ears
brown eyes (dom over blue)
what are 3 broad categories of genetic diseases discussed in lecture?
single gene disorders
chromosomal disorders
complex/multifactorial disorders
what are single gene disorders + examples
these are gene mutations
cystic fibrosis, sickle cell disease
chromosomal disorders + example
abnormal number of structural arrangement of chromosomes
downs syndrome
complex / multifactorial disorders
acquired mutations (cells dont replicate like they should)
have exogenous causes like environment, diet, etc
who made the Lamarckian theory
jean baptiste lamark
lamarckian theory
acquired traits in response to environment experienced over the lifetime will be transmitted to offspring
epigenetics
the study of heritable changes caused by mechanisms other than changes in underlying DNA sequence
factors influencing epigenetic variation
stress
drug use
social interactions
pesticides
smoking
nutrition
hormones
what can epigenetic inheritance system also be described as?
soft inheritance
what can genetic inheritance also be described as?
hard inheritance
Changing what DNA gets read leads to…
expression of diff genes
producing diff proteins
results in diff physiological outcomes
impacts behaviour
are epigenetic changes potentially reversible?
yes
are genetic changes potentially reversible?
no
behavioural epigenetics
experiences in our environment that can lead to long term effects on the brain and subsequently behaviour
can epigenetic behavioural changes be passed across generations?
yes
define nurture
experiences occurring during fetal development can have long term effects
brain and body are developing rapidly, providing window of opportunity for variation
when dna is read, it is also _____
expressed
when gene expression is repressed or turned off, what happens?
methylation occurs, meaning a methyl group is added
when gene expression is expressed or turned on, what happens
acetylation
acetyl group added
describe the Michael Meany study on rat mothering and how it callibrates brain response to stress in rat pups
Rats raised by less-nurturing moms have more methyl groups attached to promoter region (the ‘on’ switch) of the GC receptor gene
o These methyl groups block access by transcription factors that turn the gene on
As a result, fewer receptors are produced, and rat cannot shut down stress response as easily
o Good news: enzymes that reverse DNA methylation of GC receptor gene also reverse effects of unenthusiastic mothering on pups hormonal and behavioral
responses to stress (The Seductive Allure of Behavioural Epigenetics, SCIENCE, 2010)
1998 quebec ice storm
DNA methylation in offspring
o Epigenetic change due to objective levels of hardship vs. sustained subjective stress ^not the mother’s perceived experience - Ex. epigenetics and agouti yellow mouse
o Agouti genes🡪 obese, yellow, disease-susceptible
▪ Can be turned off if silencing epigenetic marks around it accumulate around the agouti gene
o How the maternal environment influences disease in offspring
o Agouti rats and healthy diet
o Obesity in agouti mice
▪ Healthy foods
▪ Supplement with Vitamin B12, folic acid, choline, betains
rat study on exercising and epigenetic changes
exercised vs. non-exercised rats then exposure to swim stress test ▪ Both conditions freaked out that they couldn’t find the platform
▪ Took rats out for 24 hours and put them back in the same situation
▪ Found that rats that were exercising didn’t struggle as much in the pool (they remembered that the pool didn’t have a platform), non-exercised
rats still struggled the same amount
▪ Exercised rats had higher number of neurons in the dentate gyrus (which is a brain region related to memory)
* The histones behaved differently in exercised rats
human study on exercising and
Exercising encourages demethylation (ie., reading) of genes that
encourage energy (carb, fat, etc) metabolism
- Ex. environmental experiences
o Exposure to pesticides induces epigenetic variation in sperm, leading to infertility o These effects persist over multiple generations
There is a third influence besides nature and nurture:
epigenetics
histones + DNA =
chromatin
what determines how cells differentiate into their specific functions?
epigenetics
transgenerational inheritance of epigenetic marks
epigenetic marks can be transmitted to multiple generations if the marks are put down on our sperms or eggs
how can epiugenetic marks accumulate AFTER our birth? (rat stuff)
Glucocorticoid receptors in rats brain help rat cope with stressful situation (more receptors = better coping)
o Rat pups at birth have silencing around receptors, but if rat mother extensively grooms pups during first week, the silencing marks can be removed from the gene.
o Gene is turned on and it stays on throughout their lives.
are epigenetic marks reversible? how? implications?
Too many silencing marks around tumour suppressor genes = gene turned off (more likely to get tumours/cancer)
o Scientists can target these silencing marks are remove them
o Also could be used for lupus, alzheimers, diabetes etc
