Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
10 Cards in this Set
- Front
- Back
|
Define Epigenetics and Epigenome |
Epigenetics - study of heritable changes in gene expressionwithout change in DNA sequence (involves DNA remodelling - methylation +histones) Epigenome - The total collection of epigenetic settings across a genome |
|
|
Explain the role of chromatin remodelling processes in theregulation of gene activity |
DNA methylation add CH3 to 5' carbon of cytosine (ONLY CYTOSINES IF FOLLOWED BY A GUANINE) within CpG islands of promotor regions (patterns can be tissue/gene/person specific) works with histones to regulate chromatin structure and gene expression high methylation = inactive transcription (eg X inactivation) |
|
|
How does DNA Methylation occur? |
DMNT (DNA methyltransferases) meditated
(reversed by DNA demethylases) DMNT1 maintains existing methylation pattern DMNT3A/3B - de novo Important in puberty epigenetic programing resets epigenetic marks (demethylation then methylation) *chart with hemi meth (passive demethylation) for just DMNT1, active for DMNT3A/3B |
|
|
When/how does DNA methylation change during development? |
middle - primordial, fertilised oocyte, sperm(slight up), egg(slight down), placenta/yolk sac low - gonadal differentiation, blastocyst high - somatic cells (down to PCGs) |
|
|
What are the 2 types of Histone modifications and when do they occur? |
Histone acetylation/deacetylation occurs when opening/condensing chromatin Acetylation - involves HATs acetyl group transferred from histone lysine->open state pos charge of histones NEUTRALISED Deacetylation - involves HDACs reverses acetylation OVERALL CHARGE OF HISTONES POSITIVE |
|
|
For Chromatin remodelling what state of acetylation and methylation must occur for transcription? |
Acetylation follows opposite of DNA methylation
DNA methylation with histone deacetylation = CLOSING (therefore no transcription) DNA demethylation with histone acetylation = OPENING (therefore transcription can occur) |
|
|
Give examples of epigenetic phenomena and explain theirmechanisms and consequences |
reprogramming in early embryo
gametogenesis |
|
|
Explain the principles of genomic imprinting and Xinactivation |
most genes are monoallelic (one gene expressed)
silencing of one allele according to parent = GENOMIC IMPRINTING (reversible, can be switched between generations eg. man receives inactive allele from mother but it is activated for mans generation) X inactivation - to allow same dosage in M/F stable across mitosis but not across generations |
|
|
Discuss how primary and secondary epimutations may cause disease |
primary - without base sequence change, reprogrammed chromatin state. may be induced by environment
secondary - caused by genetic mutation at defined locus, may involve gene/cis-acting regulatory sequence, determine disease phenotype |
|
|
Outline examples of genomic imprinting disorders and explainthe causes, pathogenesis and molecular basis of each disorder |
Imprinted gene cluster - Angelman (AS) + Prada-Willi (PWS) syndromes
neurodevelopmental disorders (cluster on chrom 15q11-13) AS - severe mental disability, microcephaly (laughter and smiling) deletions from MATERNAL
|
