Flashcards in Chapter 6- DNA and Biotechnology Deck (34)
pentose (5C sugar) bound to a nitrogenous base formed through a covalent link with C1 of sugar.
formed when one or more phosphate groups are attached to C5 of nucleoside. building blocks of DNA
5 bases in DNA/RNA
4/5. uracil (RNA or DNA)/ thymine (DNA)
backbone of DNA
sugar and phosphate- create phosphodiester bonds (phosphate makes DNA negative)
DNA is always read from 5' to 3'
2 ring structure found in both DNA and RNA (PUR As Gold, two gold rings at a wedding)
1 ring structure (CUT PYI, pie crust has one ring)
1. cytosine (DNA and RNA)
2. thymine (DNA only)
3. uracil (RNA only)
complementary base pairings in DNA
A-T (2H bonds)
G-C (3H bonds)
most DNA is a right-handed helix, turning every 3.4nm (~10 bases between each turn)
major and minor grooves in DNA
provide binding sites for regulatory proteins
zigzag appearance. left-handed helix turns every 4.6nm (~12 bases between each turn). this form may occur with a high G-C content or high salt concentration. less stable than B-DNA.
commonly used to denature DNA
heat, alkaline pH, chemicals (formaldehyde and urea)
denature vs reannealed
denature- 2 strands separated
reannealed- 2 strands brought back together
the last histone that seals off the DNA as it enters and leaves the nucleosome, adding stability
dark, dense, and silent DNA, compacted during interphase
light, uncondensed, expressed DNA (genetically active), dispersed chromatin
repeating unit at the end of DNA (TTAGGG), some of this is lost every time during replication. telomerase fixes this and is highly expressed in rapidly diving cells.
aka replication complex. specialized proteins to assist DNA polymerases.
responsible for unwinding DNA
DNA gyrase (DNA topoisomerase II)
alleviates torsional stress and reduces risk of strand breakage by introducing negative supercoils. works ahead of helicase (prokaryotes)
reading DNA template (parental strand) and synthesizing the new daughter strand. reads parent in 3 to 5 direction and builds the daughter in 5 to 3 direction.
5 classic eukaryotic DNA polymerases
1. alpha- synthesizes leading/lagging strands
2. beta- DNA repair
3. gamma- replicates mitochondrial DNA
4. delta- synthesizes leading/lagging strands, fills in gaps left behind when RNA primers are removed, forms sliding clamp to strengthen interaction b/w DNA polymerase and template strand
5. epsilon- DNA repair, forms sliding clamp to strengthen interaction b/w DNA polymerase and template strand
mutated genes that cause cancer
before genes are mutated to become oncogenes. they promote rapid cell cycle advancement more than usual.
nucleotide excision repair (NER)
eliminates thymine dimers from DNA using a cut and patch process
makes a nick in the phosphodiester backbone of the damaged strand on both sides of the thymine dimer and removed the defective oligonucleotide (based on bulge in the strand)
what can thermal energy do to DNA
cytosine deamination: los of amino group from cytosine turning it into uracil (which should not even be in DNA)
base excision repair
repairs small, non-helix-distorting mutations in other bases as well.
1. affected base is recognized and removed by glycosylase enzyme
2. apurinic/apyrimidinic (AP) site is left open aka: abasic site
3. AP site recognized by AP endonuclease that removes damaged sequence from DNA
4. DNA polymerase and ligase fill and seal the strand
exon vs intron of DNA
joining of complementary base pair sequences. can be DNA-DNA or DNA-RNA