Epigenetic Growth and Development Flashcards
What is epigenetics? (there’s 3 here - so whichever is easiest to remember)
the study of changes in gene expression or cellular phenotype, caused by mechanisms other than changes in the underlying DNA sequence
OR
is the study of how some of environmental factors can alter the way genes are epigenetically expressed , making even identical twins different
OR
the development and maintenance of an organism is orchestrated by a set of chemical reactions that switch parts of the genome off and on at strategic times
What are the three most common processes involved in bringing about epigenetic changes
DNA methylation,
histone modification,
miRNA effects
Explain DNA methylation… (lots of info here but just take a few points & don’t worry about too much detail)
DEFINITION: DNA methylation is a biochemical process involving the addition of a methyl group to the cytosine or adenine DNA nucleotides.
OTHER INFO: DNA methylation is typically removed during zygote formation and re- established through successive cell divisions during development
- most well studied epigenetic process!
- 7% of cytosine bases in mammals are methylated -> these promoter regions are called CpG islands
Within CpG islands -> methylation -> silences gene
Within CpG islands -> demethylation -> activates gene expression
Mouse: Methyl supplements during pregnancy -> changes offspring coat colour & leads to less tail kinks
Human: Methylation at birth -> child’s later adiposity
CONCLUSION: pre-birth - DNA methylation has associated disease risks; perinatal - utility in identifying individual vulnerability to later obesity and metabolic disease
Explain histone modification…
DEFINITION: The genetic material of DNA is wrapped around a set of eight histones proteins. Based on the conformational changes to the histones brought about by presence or absence of other moieties, changes in chromatin condensation occur, leading to alteration in binding ability of promoters to gene transcription sites
MODIFICATIONS INCLUDE: phosphorylation, ubiquitination, methylation & acetylation (P.U.M.A.)
OTHER INFO: Therefore epigenetic modifications of histone tails (PUMA) -> changes in gene expression, growth development and disease processes
- Acetylation MOST HIGHLY STUDIED - factors include:
HAT -> hyperacetylated -> cell growth arrest/apoptosis
HDAC -> hyopacetylated -> increase cell growth
Explain microRNA effects…
DEFINITION: single-stranded RNAs bind to mRNA leading to INACTIVATION OF mRNA. DNA methylation can influence miRNA levels, and conversely miRNA may target translation of enzymes involved in histone modification and DNA methylation
Key concepts of epigenetic modification of growth and development… (twin example is good)
DNA sequence in identical twin are exactly same, that physiological the identical twin become increasingly different over the times. why?
GENOTYPE along with epigenetic modifications can affect phenotype, however in twins, genotype is the same and so is phenotype at early life stages.
NUTRITION & DIET: increase nutrition/diet -> alters growth & development
PHYSICAL ACTIVITY
TOXICITY EXPOSURE/POLLUTION/SMOKING
STRESS: isolation, temp/season, housing, immune challenge
What is developmental plasticity?
Developmental plasticity enables an organism to respond to environmental cues and adjust its phenotypic development to match its environment
The nutrition you received in the womb; the pollutants, drugs and infections you were exposed to during gestation; your mother’s health and state of mind while she was pregnant with you — all these factors shaped you as a baby and continue to affect you to this day
The timing of epigenetic modifications…
- In pregnant adult mice exposed to estrogenic environmental endocrine disruptor -> NO CHANGES IN DNA METHYLATION
- developing fetus within these pregnant rats -> aberrant methylation that persisted after birth
CONCLUSION: Individuals may be susceptible to epigenetic modifications only during certain vulnerable periods within a lifetime!
