DNA Structure Flashcards
Rett Syndrome
- X chromosome
- neurodevelopmental affects only females
- defect in methyl-CpG-binding protein 2 in chromatin conformation
- problem in way DNA is packaged in cells, effects epigenetics
Primary structure
Covalent makeup and base pair sequence
Secondary structure
Stable structure taken up by some or all of the nucleotides
Tertiary structure
Complex folding of chromatin to form chromosomes
B-DNA
Right handed, Watson crick, 10 bp/turn
Z-DNA
Left handed, GC rich
A form
Dehydrated B form, 11 bp/turn. Planes tilted 20 degrees away from perpendicular to helixes.
-DNA-RNA hybrids and RNA-RNA double strands
Denaturation
Disruption of the non-covalent interactions holding the duplex together
Lowers viscosity and absorbs more UV (hyperchromic effect)
Viruses
Protein coat surrounding genome
Bacteria
Single Circular chromosome in nucleoidand smaller circular DNA’s called plasmids
Eukaryotes
Package DNA into chromatin
Euchromatin
Loosely packaged and transcriptionally active
Hterochromatin
Tightly package and transcriptionally inactive
Histones
Contain large amounts of basic Aminos (Lys and Arg) that are positively charged to attract neg charged DNA
Topoisomerases
Relax supercoiling and maintain neg supercoiling by nicking and resealing
DNA methylation
- Inhibit binding of trans acting factors, repressing transcription if at promoter sequences but can affect binding of repressive factors and activate transcription
- Also serve as recognition motif
DNA methyltransferases
Catalyze methylation using S-adenosyl methionine (SAMe) as donor.
Ten-eleven translocation
Enzymes that catalyze remove of DNA methylation involving multiple intermediates. Followed by base excision repair
Thymine-DNA glycoylase (TDG)
Removes thymine moieties from G/T mismatches by hydrolyzing the C-N bond between the sugar-phosphate backbone of DNA and mismatched thymine
Acetylation
Most commoner his tone modification, transfer of acetyl group from acetyl coenzyme A to the epsilon-amino of lysine
-causes naturalization of positive charged histones, decreasing affinity for DNA
