18: Genomic Regulation Flashcards
Major bond stabilizing DNA
H bonds between complementary bases
Bonds between A /T and C/G
A/T: 2 H bonds
G/C: 3 H bonds
Nt per turn for B DNA
10nt per turn
How A DNA and Z DNA are different from B
A: 11nt per turn
Z: left haded form
Nucleosome
Core of 8 histones + DNA
Charge of histones and DNA
Histones: positive
DNA: negative
Histone H1
Linker histone - separates each nucleosome
Chromatin in G1 vs M phase of cell cycle
G1: loose
M: tight
Exon vs intron
Exon: coding region
Intron: non-coding
Four characteristics of DNA replication
- Semiconservative
- Bi-directional (multiple ORIs)
- Primed by RNA
- Semi-discontinuous while synthesizing
Topoisomerases
Remove supertwisting in DNA
SsDNA binding proteins
Prevents premature annealing of single stranded DNA to double stranded DNA
DNA primase
Adds RNA primers
DNA ligase
Seals breaks/nicks in DNA after DNA Pol fills gaps
Most frequent type of DNA damage
Spontaneous DNA damage
What can takes care of epoxides that cause issues?
Cytochrome P450 enzymes
Two types of epigenetics modifications
- Gene methylation
2. Histone mods by acetylation and deacetylation
Major site of DNA methylation
A cytosine base, especially the 5’ C next to a G (5’ CG 3’)
What does methylation of 5’ CG 3’ areas do?
Cause steric hindrance of TFs in promoter region
What process is gene methylation important for?
Tissue-specific gene expression
What syndrome is caused by gene methylation
Fragile X syndrome
Mutation in fragile X syndrome
Addition of CGG nt repeats -> hypermethylation -> inactivating FMRI gene (fragile X MR 1 gene)
Symptoms of Fragile X Syndrome
Intellectual disability, problems with social interaction, delayed speech, long and narrow face, large ears, flexible fingers, large testicles
What does histone modification by acetylation and deacytlation do?
Makes DNA more or less accessible to TFs
Enzymes that acetylate and deacytlate histones
Acetylate: histone acetyltransferases (HATs)
Deacetylate: HDAC
What type of gene silencing can lead to cancer?
Silencing tumor suppressor genes
Clinical associations of Xeroderma Pigmentosa
High photosensitivity, pigment changes, prone to melanoma and squamous cell carcinomas
Cockayne Syndrome clinical associations
Neurologic delay, photosensitivity, progeria (premature aging), common hearing loss and eye abnormalities
