Units 6 Flashcards
DNA
double helix structure composed of two strands held together by hydrogen bonds between nitrogenous bases. stores genetic information
RNA
single stranded structure that uses uracil instead of thymine, exists for a short amount of time and is used for transcription
purines
adenine and guanine, double ring structure
pyrimidines
thymine, uracil, cytosine, single ring structure
nucleosomes
dna wrapped around histomes that pack into chromatin fibers
exons
coding regions with genetic data
introns
noncoding regions that separate exons
linear chromosomes
chromosomes that use histomes to pack themselves
circular chromosomes
smaller prokaryotes
plasmids
small, circular units of dna, chunk of dna that can hold as little as one gene, double stranded
bacterial conjugation
bacteria exchange (donate plasmids), plasmid is replicated and sent through channel
prokaryotic dna
1 circular chromosome (like string), plasmid, smaller genome, no organelle dna
eukaryotes
many linear chromosomes, limited plasmid, larger genome, organelle dna
conservative theory of replication
would happen if both strands of dna molecule stayed bonded and intact while serving as a template for an identical molecule
semiconservative theory of replication ***
two original strands separate and each serves as a template for a new strand
dispersive theory of replication
original strand is cut every ten nucleotides to prevent tangling
helicase
ATP powered enzyme that pushes apart the two strands of DNA, regions of helicase interact with nucleotide bases and destabilizes the hydrogen bonds… “unzipping”
topoisomerase
prevents supercoiling by changing 3d shape of DNA, it relieves contortions by cutting sugar phosphate backbone –> contortion unwinds, then topo reconnects strands to original position AT THE REPLICATION FORK
primase
adds an RNA primer to exposed strand, giving DNA polymerase an exposed 3’ hydroxyl group that it can add nucleotides to
DNA polymerase
ensures base pairing occurs between free nucleotide and template, then it catalyzed formation of phosphodiester bonds between nucleotides CAN ONLY ADD 5’ TO 3’ but attatches to 3’ end of the original strand
leading versus lagging strand
leading strand can have nucleotides added continously while lagging has to attatch to newly opened template strands
okazaki fragments
gaps on lagging strand
RNAse
breaks down RNA primers
ligase
fills in gaps on lagging strand
false positive
incorrect detection of viral presence, prevented by control sample
false negative
incorrect indication that virus is not present, prevented by amplifying the sequences of DNA
why do viruses mutate
there are a lot of them, quick replication cycle, large scale replication, error frequency
nucleic acid detection test order
collect sample, DNA extraction, reverse transcriptase to convert RNA to DNA, PCR to amplify gene segment, detect with electrophoresis
steps of electrophoresis
prepare gel and use comb to make wells, place tray into chamber and cover with aquous buffer solution, load sample into wells, put on lid and connect to power supply (DNA HAS NEGATIVE CHARGE), stain and analyze gel, create standard curve to derermine size of your fragments
centrifuge
uses centrifugal force to separate liquid and solid
pellet
stuff at the bottom
supernatent
liquid on top
why do smaller dna fragments move further
they slip through the pores in the agarose easily
