Page 8 Flashcards
(15 cards)
DNA methylation
Covalent modifications of mammalian DNA occuring via the methylation of cytosine, typically in the context of the CpG dinucleotide.
DNA methyltransferases (DNMTs)
Enzymes that establish and maintain DNA methylation using methyl-group donor compounds or cofactors. The main mammalian DNMTs are DNMT1, which maintains methylation state across DNA replication, and DNMT3a and DNMT3b, which perform de novo methylation.
Epigenetics
The study of heritable changes in gene expression of cellular phenotype caused by mechanisms other than changes in the underlying DNA sequence. Epigenetic marks include covalent DNA modifications and posttranslational histone modifications.
Epigenome
The genome-wide distribution of epigenetic marks.
Gene
A specific deoxyribonucleic acid (DNA) sequence that codes for a specific polypeptide or protein or an observable inherited trait.
Genome wide associated study ( GWAS)
A study that maps DNA polymorphisms in affected individuals and controls matched for age, sex, and ethnic background with the aim of identifying causal genetic variants.
Genotype
The DNA content of a cell’s nucleus, whether a trait is externally observable or not.
Histone acetyltransferases (HATs) and histone deacetylases (HDACs)
HATs are enzymes that transfer acetyl groups to specific positions on histone tails, promoting an “open” chromatin state and transcriptional activation. HDACs remove these acetyl groups, resulting in a “closed” chromatin state and transcriptional repression.
Histone modifications
Post translational modifications of the N-terminal “tails” of histon proteins that serve as a major mode of epigenetic regulation. These modifications indlude acetylation, phosphorylation, methylation, sumoylation, ubiquitination, and ADP-ribosylation.
Identical twins
Two individual organisms that originated from the same zygote and therefore are genetically identical or very similar. The epigenetic profiling of identical twins discordant for disease is a unique experimental design as it eliminates the DNA sequence, age, and sex differences from consideration.
Phenotype
The pattern of expression of the genotype or the magnitude or extent to which is is observably expressed- an observable characteristic or trait of an organism, such as its morphology, development, biochemical or physiological properties, or behaviour.
Observable characteristics as a result of genotype expression are known as
Phenotypes.
Although identical twins share a common genotype, their ___ becomes more dissimilar as identical twins age.
Epigenetic patterns.
In rats, increased amount of ___ by the mother rat ___ the expression of the glucocorticoid receptor in the hippocampus (a brain structure associated with stress responsitivity as well as learning and memory). This resulted in ___ hormonal response to stress compared with adult animals reared by mothers who engage in lower levels of this behaviour.
Licking; increased; lowered.
Identical twins share an identical genome, but we know that they are not the identical person (e.g. many have different preferences, behaviours, personality, etc). One possible explanation for differences is:
Epigenetic patterns become more dissimilar with age.
