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ADVANCES: Nutrition and epigenetics part 1 - Coggle Diagram
ADVANCES: Nutrition and epigenetics part 1
Definition and example of epigenetics: study of mechanisms alter gene expression states without changing DNA sequence
epigenetics led to visable differences between 2 cats despite identical DNA
human has 22 pairs of autosomal chromosomes plus xx / xy - cats have 18 pairs plus xx/ xy
animal cloning: 1. need cell from cat being cloned 2. need to put DNA into sit without DNA and implant into surrogate mother (mother )
coat colour development- early in development (clump of cells undeveloped- blastocystic), one copy of X chromosome gets switched off randomly (either black or orange pigment). Becuase process is random, this leads to different coat patterns. Non visable effects can happen, do not expect clones to be carbon copies
! LOOK OVER EPIGENETICS OF COLOUR DEVELOPMENT DIFFERENCES AT CELLULAR LEVEL !
Epigenetics: stable and heritable alterations in gene expression that do not involve a change in DNA sequence
Epigenetic heritability
epigenetic effects are mitotically stable (as cell undergoes mitsosis, epigenetic info is replicated)
epigenetic heritability may not be identical to genetic heritability
transmission across generations of cells of the same origin
some evidence of transmissions cross generations of animals
What are the effects of epigenetics?
early development establishing cell lineages
foetal origins of adult disease
x chromosome inactivation in females
expression of imprinted genes
ageing and cancer
probably many others
DNA structure
DNA has to be condensed, structured, organised and archived so that it fits within the nucleus and still functions properly
DNA double helix packed further in nucleus into chromatin which is DNA wrapped around histone proteins . Helps to pack and protect and is IMPORTANT IN GENE EXPRESSION
Euchromatin (active gene expression) is chromatin unravelled to make DNA accessible. Epigenetic factors regulate local chromatin structure for this gene expression
Heterochromatin is DNA wrapped up tightly and gene expression switched off
how does epigenetic regulation actually work
epigenetic regulation is achieved via changes in structure and not sequence
epigenetic effects are controlled by epigenetic marks
Methylation- !slide 25/26 look over again !
DNA can be methylated on different bases and at different positions of the bases. If methylated, signal for cell for DNA to be transcribed
In higher eukaryotes the common modification is addition of methyl group at C5 position of cytosine base, donated by SAM (does not affect DNA code) and performed by DNA methytransferase.
De novo methylation
Maintenance methytransferases methylate DNA where one strand is ALREADY METHYLATED (e.g. during DNA replication) - DNMT1
De novo methyltransferases methylate cytosines in regions not previously methylated (DNMT3A and DNMT3B)
Demethylation of DNA: passive demethylation (maintenance methylation blocked during replication) or active ( 5-methyl cytosine oxidised yb TET dioxygenases and so product is recognised as DNA damage and repaired)
DNA methylation and gene silencing: DNMT can bind to methylated CpG and block RNA poll 2.
? other mechanism slide 31?
Epigenetic effects of chromatin results from:
DNA methylation
histone modfication
non-coding RNAs
polycomb proteins
probably other things yet to be characterised.