Symes DNA Structure and Function Flashcards
B-form DNA
Hydrated, 10 bp/turn
- right handed
- wider major groove (allows access for proteins)
A form DNA
Low humidity, 11 bp/turn
- right handed
- narrower, deeper major groove
Z form DNA
GCGCGCGC, 12 bp/turn
- left-handed
- spreads out actively transcribing genes
2º DNA stabilizing factors
H bonds, vDw interactions, ions
2º DNA destabilizing factors
electrostatic repulsions, PO4- (at pH 7)
What wavelength do NTs and nucleic acids absorb light at
260 nm
Does single or double stranded DNA absorb more light
Single-stranded absorbs more light because the bases are exposed
- still the same wavelength
What is the Tm
Temperature at which 50% of DNA is denatured
5 HAART Inhibitors
1) Nucleoside Reverse Transcriptase Inhibitors (NRTIs)
2) Non-nucleoside RTIs
3) Protease Inhibitors
4) Entry Inhibitors
5) HIV Integrase Inhibitors
How do Nucleoside Reverse Transcriptase Inhibitors work?
Inhibit addition of NTs to a chain using a nucleoside analog
- AZT, Acyclovir (only uses the viral kinase)
A supercoil which is underwound is positive or negative
Negative
A supercoil which is overwound is positive or negative
Positive
Is natural DNA negatively or positively supercoiled
Negative (underwound)
Topoisomerase 1 function
Breaks one strands and changes it by +1 or -1 supercoils
- requires the DNA to be strained (overwound or underwound)
Topoisomerase 2 function
Cuts 2 strands, changes the number of supercoils by 2
- removes supercoiling 2 twists at a time
- in prokaryotes, it can add supercoils to new DNA
How do topoisomerase inhibitors work?
Inhibit the re-ligation function of the enzyme
Are the topoisomerases the same in prokaryotes and eukaryotes
Nahh bb diff versions
3º structure of DNA in eukaryotes
Histones (small, positive proteins)
H1 function
Linker DNA for higher-order structures
H2A function
Combined with H2B, H3 and H4 in the nucleosome core
- DNA wrapped around core is same length as Okazaki fragment
What are highly repetitive sequences
Short, tandem, AT-rich sequences found in eukaryotes
- greater than 300k copies/genome
- 10% of genome
- ex. telomeres
What is a solenoid
Complex of nucleosomes that causes a 35-40x shortening of DNA
- 6 nucleosomes per turn
What are moderately repetitive sequences?
Code for highly-used genes in eukaryotes
- SINES/LINES space out actively transcribing genes
What are unique/single-copy sequences
40-60% of eukaryotic genome
- grouped in families
- includes pseudogenes: genes which are never transcribed
- housekeeping genes
Whats special about the beta-globin family of genes
They are spreading out on different chromosomes, and are expressed in different tissues at different ages
Myotonic Dystrophy Type 1
Results of CTG-repeats
- increased number increases severity by decreasing onset age
- due to the polymerase slipping on trinucleotide repeats
Concept of anticipation
Severity of a disease increases with each successive generation
