Lecture 6 Flashcards
DNA Methylation
Epigenetic Change
Silences transcription
Can be detected by bisulfite sequencing
Bisulfite Sequencing
Treating DNA with bisulfite converts cytosine but not 5-methylcytosine
Nucleosome
Fundamental unit of chromatin
Relaxed vs Condensed Chromatin
Relaxed—> DNA is accessible
Condensed—> DNA inaccessible
Heterochromatin vs Euchromatin
Heterochromatin: small, dark staining, irregular, adjacent to nuclear envelope
Euchromatin: dispersed, not easily stained, abundant in cells with active transcription
Position-Effect Variegation
Gene normally in Euchromatin is juxtaposed with heterochromatin
—> cells of the same type can express differently
Things that affect readout of the DNA through affection levels and types of chromatin modifications
Diet, toxins, stress
Remodeling of Chromatin for Transcription
Acetylated histone tails to allow for transcription factors
Decompacts
Reader Proteins:
Coordinate and integrate various modification signals
Bring additional enzymatic machinery to specific chromatin loci
Determine substrate specificity of enzyme
RNAi
Sense and antisense RNA can turn off endogenous gene
RNAi action
Presence of double stranded RNAs cause cells to specifically degrade any other using small interfering RNAs
RNA Interference Dicer
RNAse III
Generates siRNA
RISC
Contains siRNA
Finds/destroys mRNA of complementary sequence
Contains Argonauts (endonuclease to cleave hybrid in the middle)
SiRNA vs miRNA
Si: exogenous, double stranded, taken up by cells, viral infection
mi: endogenous, single-stranded (made by cells)
Transposons
2 types
Non-autonomous Elements- need presence of other transposable element
Autonomous Elements- transpose themselves
