NUCLEIC ACIDS Flashcards
isolated what he called nucleinfrom the nuclei of pus cells
Friedrich Miescher
The source of genetic information in chromosomes
nucleic acids
DNA is found in
Nucleus, mitochondria, chloroplasts
Nucleotides have 3 parts
5-carbon sugar (pentose)
nitrogen containing base (CHN)
Phosphate group
double ringed structure
purine
(adenine and guanine)
single ring
pyramidine
(cytosine and thymine)
no O atom on carbon 2’.
DNA
Nucleoside=
Nucleoside= N base + 5-C sugar
nitrogen base linked by a glycosidic bond to C1’ of a sugar (ribose or deoxyribose).
nucleoside
named by changing the nitrogen base ending to
___ purines
____ pyramidines
-osine
-idine
−OH on C5’ of a sugar bonds to phosphoric acid
nucleotide
Nucleotide =
nucleoside + phosphate
a nucleoside that forms a phosphate ester with the C5’ –OH group of a sugar (ribose or deoxyribose).
nucleotide
Raw materials for DNA biosynthesis
dATP, dGTP, dCTP, dUTP
Raw materials for RNA biosynthesis
ATP, GTP, CTP, UTP
Secondary messengers in hormones action.
cAMP, cGMP
nucleotides are joined by
phosphodiester bonds
secondary structure of RNA
cloverleaf tRNA
What are the four loops in secondary structure
D loop
Anticodon loop
variable loop
T ¥ C
What are the four arms of secondary structure
amino acid arm
D arm
T¥ C arm
Arrange according to their percentage
tRNA
rRNA
mRNA
rRNA (75)
tRNA (10-15)
mRNA (5-10)
Ribosomes consists of
rRNA-
Proteins-
65
35
The base chain is written in the _____ direction
5–>3
A=T
G=C
what rule
chargaff’s rule
X-ray Diffraction Refined Structure
Franklin, Wilkins
Adenine is alwayslinked by ____ bonds with Thymine
two H bonds
Guanine is always linked by ____^hydrogen with Cytosine
three
proposed by Watson & Crick; standardDNA structure
right handed helix
atlow humidity,the DNA molecule will take the
A form
the minimum functional unit in DNA
gene
short coding sequences
exons
a longer intervening noncoding sequence
introns
Between replications, the DNA is stored in a compact ball called
wrapped around the protein called
to form
chromatin
histones
nucleosomes
DNA & RNA specific absorption at max =
260 nm
The more G-C content, the ___ Tm value.
higher
Characteristics of DNA replication
semi conservative
bidirectional
semi-discontinuous synthesis
each daughter duplex contains one strand from the parent duplex
semi conservative
is first made as short chains
lagging strand (Okazaki fragments)
precursors of DNA replication
dNTPs
Unwinds DNAdouble helix
helicase
Catalyzessynthesis of RNA primers
Primase
Catalyzeschain elongation
DNA polymerase III
Involvedin the excision of primers and filling up of gaps
DNA polymerase I
Catalyzesthe formation of a phosphodiester linkage between a 3’hydroxyl at the end of one DNA strand and a 5’ phosphate at the end of another strand
DNA ligase
replicates DNA only 5’ to 3’
DNA polymerase III
one of the major post-replicative reactions.
methylation
Site of methylation of eukaryotic DNA is always on
cytosine
Transcription has 3 stages
Initiation
Elongation
Termination
stretch of 6 nucleotides
Pribnow box
a 2ndnucleotide sequence, TTGACA, located about 35 bases to the left of the transcription start site
-35 sequence
the promoter region has been recognized by the
holoenzyme
+ supercoil (ahead of the transcription site) –relaxed by
gyrase
➢-supercoil (behind) –relaxed by
topoisomerase
linkage of 7-methylguanosine to the 5’ terminal residue.
capping
attachment of an adennylate polymer (poly A, 20~250 nucleotides) at the 3’ terminal.
tailing
While the mRNA is still in the nucleus, the ___ are removed from the pre-RNA
introns
Inprokaryotes(bacteria and archebacteria), transcription of proteins is regulated by an ___
operon
consists of a control siteand the genes that produce mRNA for lactose enzymes
lactose operon
When there is no lactose in the cell, a ____ produces a _____ protein prevents the synthesis of lactose enzymes
regulatory gene
repressor
Translation Five Stages
Activation of amino acids
Initiation of translation
Elongation
Termination and ribosome recycling
Folding and post-translational processing
Enzymatic synthesis of aminoacyl tRNA molecules
activation of amino acids
Binding of mRNA and N-formylmethionineto ribosome
initiation of translation
Binding of aminoacyl tRNAs to ribosome
formation of peptide bonds
elongation
an adapter molecule, which recognizes an amino acid on one end and its corresponding codon on the other, is required for translation. This adapter molecule is
tRNA
have self-checking functions to prevent incorrectly paired amino acyl tRNAs from forming.
Aminoacyl tRNA synthetases
a sequence of amino acids in a mRNA that determine the amino acid order for the protein.
genetic code
3 stop codons
UUA
UAG
UGA
There are how many triplets of amino acids
61
First amino acid is
methionine
The addition of a.a to the carboxyl end of the growing polypeptide chain.
elongation
By each cycle the polypeptide has grown by one residue and consumed
two GTP
Two types of mutation
point mutation
base deletion or insertion
Changing a single nucleotide base on the m-RNA chain
point mutation
The codon containing the changed base codes for the same amino acid
silent mutation
The change results in a new different amino acid
missense
The change leads to premature termination if the codon containing the changed base become a termination codon.
non-sense mutation
Insertion or deletion of one or two bases will alter the reading frame and this cause extensive change in the translated protein
frame shift mutation
What are the different mutagens?
radiation
chemical mutagens
Disrupt DNA and RNA replication
nucleotide analogs
Result in base-pair substitutions and missense mutations
nucleotide-altering chemicals
Result in nonsense mutations
frameshift mutagens
