EXAM2_L13_ Chromatin_Structure Flashcards
Sugar + Base called?
Sugar + Base + Phosphate called?
Nucleoside
Nucleotide
NTP’s & dNTP’s - what is? what makes?
What is triphosphate necessary?
NTP’s-Nucleoside triphosphates ( used to make RNA)
dNTP- deoxyribonucleoside triphosphate (used to make DNA
necessary for energy of construction
What are the purines? how many rings?
Adenosine (adenine base) and
Guanosine (guanine base)
form 3 H bonds
two ring structure
What are the pyrimidines? how many rings?
Cytosine
Thymine (unique to DNA)
Uracil (Unique to RNA)
one ring structure
What is special about each carbon on the sugar?
1’,2’,3’,4’,5’
1'- attachment site for Nitrogenous Base 2' - OH (RNA-ribose) or H (DNA-deoxyribose) 3'- site of new nucleotide addition 4' 5'- Attaches Phosphate group
Bonds that keep backbone together?
negatively charged covalent phosphodiester bonds
how are nucleotides attached to each other?
what makes the backbone?
covalent phosphodiester bond of 3’ sugar of one nucleotide to the 5’ phosphate group of the next nucleotide
- sugar-phosphate linkages form the phosphodiester backbone of DNA + RNA
How do you determine the 5’ or 3’ end ?
The 5’ end - consists of a 5’C Usually bound to a phosphate (not linked to another sugar)
-3’ end is bound to an -OH instead of another sugar
Why is hydrogen bonding critically important? 3 reasons
- stabilization of dsDNA (creates double strand)
- Transcription (correct structure)
- DNA Replication (correct incorporation determined by H bonding)
Ie: damage to nucleotide causing change in H bonding will result in wrong nucleotide put inside daughter strand (mutation)
DNA Structure of bases, and sugars.
what happens to negative phosphates?
bases stack parallel (dinner plate), perpendicular to axis of helix & create base-stacking forces between two bases on the same strand (STABILIZES DNA)
- sugars are perpendicular to the bases
- P’s have ionic bonding of divalent cations (Mg2+) that shields negative repulsion of phosphates
diploid human cell contains____base pairs stretched out to _____ long.
6 BILLION base pairs stretched out to 6’ long
Histones vs nucleosome. how many bp? wraps?
Chromatosome?
- Histone is octomer (protein) that DNA wraps around
- Nucleosome is (8 core histones + DNA)
- 146bp wraps 1.75 times around histone core
- Chromatosome-H1 linker histone covering 165bp DNA
10nm fiber 30nm fiber (what stabilized by? 3 things)
- 10nm fiber- beads on a string- 20-80 bp
- 30nm- condensed 10nm fibers (stabilized by H1 Linker, histone N-terminal tails, linker DNA.)
- consists of nucleosomes & chromatosomes
What stage fiber is found in interphase euchromatin?
10nm-30nm fibers.
what are loop domains? what stage? activity?
decondensed 10-30nm fibers organized and not actively dividing
