Nucleotides/DNA Structure Flashcards
Purines
Adenine
Guanine
Nucleic Acids - components
Bases, sugars, phosphate groups
Prymidines
Cytosine
Thymine
Uracil
Nuclosides
Purine and Prymidine bases and pentose (ribose or deoxyribose)
Nulceotides
Phosphorylated nucleosides
Oligonuclotides
Short polymers of nucleotides
Ionic forces & DNA
Ionic forces also affect the stability and confirmation of double helix
DNA ligase - fxn
Forms phosphodiester bonds between free 5’ and 3’ ends of DNA
Active site of enzyme
contains substrate bindind site and the catalytic site
Nucleases - fxn
Hydrolyze phosphodiester bonds
Exonucleases - action
cleave the last nucleotide residue a either of the two terminals.
Endonucleases - action
cleave phosphodiester bonds in the interior
DNA confirmations
B, Z, A
Common cell DNA confrimation
B
Z -DNA
occurs within DNA sequences that control gene transcription
A-DNA
form taken by DNA-RNA hybrid during transcription
Topoisomerases - fxn
specific enzymes that regulate superhelices
Topoisomerases - types
Type I
Type II
Gyrases
Type I Topoisomerases
break only one DNA strand and alllow it to rotate about the other to relive the super coil. Also reseal the break that was created after supercoild relieved
Type II Topoisomerases
beak both DNA strands, relax the supercoil and then reseal the DNA.
REUIRES ATP
Gyrases
Topoisomerases that relive supercoiling generated by the unwinding of DNA
Topoisomerases - clinical function
Used as targets for antimicrobial and antineoplastic agents. They convert Topoisomerases into DNA-breaking agents by specifically interfering with DNA ligase activity of the topoisomerase.
Alternative DNA Confirmations
DNA Bending
Cruciforms
Triplex DNA
Quadruplex DNA
Cruciforms - def., fxn
regions of DNA in which interchain hydrogen bonds are disrupted and interchain bonds form
fxn in control of replication and transcription
Hoogsten pairing
pairing of bases occurs in different faces of bases than do Watson and crick pairing
Triplex DNA
Occurs in DNA w string of purine bases
Fxn in transcription control, initiation and termination of replication, exchanging telomeres stability
Third strand pairs with Hoogsten pairing
triple stranded DNA - clinical
associated with hereditary persistence f fetal hemoglobin
Quaduplex DNA
forms in immunoglobulin genes that undergo recombination
also occurs in teleomeres
Histones
Basic proteins in eukaryotic DNA
NOT in prokaryotic DNA, instead HU protiens
Chromatin
DNA with its associated proteins
During cell division, becomes condensed to chromosones
Chormosones - components
Condensed chromatin
Centromere
Telomere
Centromere
site of attachment of the chromosome to the mitotic spindle
Telomere
ends of chromosomes
Structural genes
DNA coding sequences that code for protein
