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60 Cards in this Set

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describe purines and pyrimidines
heterocyclic
weakly basic
relatively insoluble in water (nucleotides are soluble)
unsat w/ conjugated dbl bonds
glycosidic bond
links the base to the sugar
importance of negativity of phosphate
makes nucleic acid polyanions. crucial to function
A DNA
more tightly wound, has grooves of equal width. predominates in DNA-RNA hybrids. Forms when DNA is dehydrated
Z DNA
has no grooves and bases positioned towards periphery of left handed helix
prok vs euk genome size
euk is 1000 times bigger
packing of prok DNA
supercoiled and attached to an RNA-protein core in large loops
-called the nucleoid structure
chromatin
euk DNA plus various proteins
beads on a string look
nucleosomes
histones plus DNA
histones
small basic proteins containing lots of lysine and arginine (+)
-euk have five classes
-positive histones attracted to neg sugar-phosphates on backbone
nucleosome core
histone octamer of two of each histones with about 140 bp wrapped around it
linker DNA
part of it complexed with H1 that locks the coiled DNA in place on the histone octamer
solenoid structures
further compaction of the DNA
-helical structures
-associate through weak interactions between H1 molecules
heterochromatin
densely packed DNA-seen in interphase
euchromatin
loosely packed DNA-in interphase
importance of mtDNA mutations
OXPHOS diseases-associated with brain and muscle, where large amts of ATP are formed
rRNA
accounts for 80% of RNA in cells
-very stable, integral part of RNA
-contain stem loop structures
tRNA
carries activated amino acids to ribosomes for polypeptide synthesis
-smallest RNA
mRNA
Carry sequence information from DNA to ribosomes
-translated by ribosomes/tRNA to form proteins
-rapidly degraded by nucleases
erythromycin
used as an antibiotic
-inhibits protein synthesis by binding the 50S ribosomal unit in prok.
modified nucleotides in tRNA
ribothymadine
dihydrouridine
pseudouridine
structure of tRNA
all have three arms:
1. D arm, contains dihydrouridine
2. anticodon arm
3. TC arm, contains ribothymadine and pseudouridine
4. some contain variable arm as well
role of snRNA
recognize key RNA sequence elements at splice sites
-allow spliceosome to correctly cut out introns
-allow for alternative splicing
ribozyme
enzymes whose catalytic sites contain RNA
4 other types of RNA
1. sn ribonuclear proteins
2. ribozymes
3. RNA "primers" for DNA synthesis
4.RNA genome of retroviruses
5-fluorouracil
cancer chemotherapeutic agent. Inhibits synthesis of thymine. Used for colon cancer treatment.
Doxorubicin
slips b/w stacked base pairs of DNA
-DNA cannot act as template for transcription/translation
-used in treatment of solid malignancies (ex: breast cancer)
AZT
blocks viral DNA polymerase (reverse transcriptase) activity
3 R's of DNA
1. Replication
2. Repair
3.Recombination
requirements of DNA replication
1.template
2. primer
3. precursors
4.enzymes
helicase
unwinds the DNA
topoisomerase
breaks and rejoins the dbl helix. prevents knot formation
single stranded DNA
prevents the single strand of DNA from recombining
RNA primase
initiates the first nucleotides of the leading strand and the okazaki fragments
DNA polymerase III
elongation of new strands. goes in 3'->5' direction
RNAase H, FENI
removes primers
DNA pol I
replaces RNA primer
DNA ligase
connects the okazaki fragments and other loose DNA fragments
Tsu
a bacteria that blocks helicase activity
DNA gyrase
induces or removes supercoiling of DNA
-absent in euk cells
telomerase
prevents chromosomes fusing
DNA replication in prokaryotes
bidirectional until meet at termination point
-primase forms RNA primer
-girase unwinds the DNA
-single stranded DNA proteins bind
-
replisome
protein machinery that carries out the polymerization reaction
steps of e.coli replication
1. primase lays primer
2. DNA Pol III lays down the DNA
3.DNA Pol I removes the primer
4. Pol I fills in the gaps
DNA pol I
repairs DNA and participates in DNA synthesis of one strand
DNA pol II
role in DNA repair
DNA pol III
major role in DNA replication enzyme. responsible for chain elongation
eukaryotic DNA polymerases
at least 15
very low error rate
okazaki fragments
DNA pol cannot initiate!
-RNA polymeraes (primase) initiates oligonucleotide primer
-DNA pol III uses primer to start lagging strand DNA synthesis
Proofreading tools
1. DNA pol III has 3' to 5' proofreading
2.pol III can catalyze chain elongation and degradation
3.exonuclease activity
4. post-replication mismatch repair
what happens in gap 1 of cell cycle
cells increase in size, produce RNA and synthesize proteins
-G1 checkpoint
what is G0
cells may leave cell cycle and quits dividing. may be temporary or more permanent
synthesis phase of cell cycle
DNA replication takes place
what is G2 of cell cycle
cell continues to grow and produce new proteins.
-G2 checkpoint for entering mitosis
three possible fates of DNA damage
1. cancer
2. senesence
3.apoptosis
4 types of DNA repair
1. base excision repair
2. nucleotide excision repair
3. mismatch repair
4. transcription coupled repair
translocation
exchange of chromosome segments b/w two usually nohomologous chromosomes
-cause of Burkitt's lymphoma
transposons
jumping genes
mobile DNA sequences that may encode transposase
-found in the junk DNA
what do transposons code for?
1. may have regulatory function and code for RNA
2.code for drug resistant markers
3. enzymes degrading toxic and carcinogenic compounds
telemorases
act to maintain the length of the telomeres
-are ribonucleoprotein complexes containing a small RNA molecule that serves as a template