Molecular Bio (Chp 4) Flashcards
Purine bases
A and G
two rings
(mnemonic: silver (AG) is pure)
Pyrimidine bases
C, U, and T
single ring
(mnemonic: pyramids are sharp and CUT you)
phosphodiester bond
covalently links nucleotides in DNA chain
H bonds in DNA
(Purine-pyrimidine)
A-T (2 H bonds)
G-C (3 H bonds)
DNA structure characteristics
- double stranded
- antiparallel (5’ on one end paired with 3’ of other)
- coiled
of chromosomes in humans
46 (23 inherited from each parent)
prokaryote (bacterial) genome
single circular chromosome
viral genome
linear or circular DNA or RNA
DNA gyrase
(prokaryote)
uses ATP E to twist DNA
Packing/condensing of human DNA
- wrapped around histones
- nucleosomes (resemble ball on a string) = wrapped around 8 histones
- chromatin - wrapped nucleosomes
centromere
region of chromosome where spindle fibers attach during cell division (attach via kinetochores)
transcription
DNA (T) > RNA (U)
translation
RNA > proteins
accomplished by the ribosome
Central Dogma
DNA > RNA > protein
information DNA is used to create actual products (proteins - ex: enzymes, structural proteins, etc.)
codon
nucleic acid word (3 nucleotide letters)
stop codons
also called nonsense codon
UAA - your are annoying
UGA - you go away
UAG - you are gone
DNA code
no ambiguity vs degenerate
no ambiguity - DNA code can only be read one way
degenerate - two or more codons coding for the same amino acid
replication
duplication of DNA - occurs during synthesis phase of cell cycle
- semiconservative
helicase
enzyme that unwinds and separates double helix at origin of replication
topoisomerase
enzymes that cut one or both strands and unwrap DNA helix > releases excess tension caused by helicase
single strand binding protein (SSBPs)
protects DNA that has been unpackaged in prep for replication and keeps separated
DNA polymerase
catalyzes elongation of daughter strand using parental template
- checks each new nucleotide to make sure it forms correct base pair
- polymerization occurs in 5’ to 3’ ALWAYS
- requires a template and primer
okazaki fragments
small chunks of DNA comprising lagging strand
DNA pol III
v fast, v accurate elongation of leading strand
DNA pol I
adds nucleotides at the RNA primer but more slowly than DNA pol III
- important for excision repair
germline mutations
mutations that can be passed onto offspring
somatic mutations
mutations in nongametic cells > not passed on to offspring
point mutation
single base pair substitutions (ex A in place of G)
can be:
-transitions - sub pyrimidine for another pyrimidine
-transversions - sub pyrimidine for purine
types:
- missence, nonsense, and silent
missence mutation
a point mutation that causes one amino acid to be replaced with a different amino acid
nonsense mutation
a point mutation that causes a regular codon to be replaced by a stop codon
> prematurely shortens the protein
silent mutation
a point mutation where a codon is changed into a new codon that codes for the same amino acid
> no change in amino acid sequence
Insertion mutation
addition of one or more extra nucleotides into the DNA sequence