Quiz 3 Flashcards
nitrogenous base of nucleotides include
- 2 types of purine
- 3 types of pyrimidines
NucleoTIDE contains
- ribose or deoxyribose sugar
- one or more phosphate group
- nitrogenous base
DNA contains
- Guanine
- Adenine
- Cytosine
- Thymine Deoxyribonucleotide
RNA contains
- Adenine
- Guanine
- Cytosine
- Uracil ribonucleotides
___ Enable them to undergo keto-enol tautomerism
aromaticity and electron rich nature of pyrimidines and purines
Protonation states of nitrogen determines
wether they can serve as H-bond donors or acceptors
Aromaticity also accounts for ____
Absorption of UV light; the peak absorbance [maximum] is 260nm
common purine bases
- adenine
- guanine
UV absorption spectra
peak absorbance is at 260nm
common pyrimidine bases
- cytosine
- uracil
- thymine
nucleotide base is linked to the sugar, ribose via
glycosidic bond
nucleotides are named by
adding -idine to the root name of pyrimidine or -osine to the root name of a purine
Sugars
can make nucleosides more water soluble than free bases
Nucleosides
get their sides from glycosides
The common nucleosides bases are shown as
anti
where do nucleotides get their tides from
phosphatides [ molecules linked to phosphate ]
most nucleotides are
ribonucleotides, RNA
DNA is a
deoxyribonucleotide
____ have many functions in the cell
ribonucleotides
ATP
is central to energy metabolism
GTP
drives protein synthesis
CTP
drives lipid synthesis
UTP
drives carbohydrate metabolism
Formation of ADP and ATP by the successive addition of phosphate groups via
phosphoric anhydride linkages aka phosphoanhydride bond
- link phosphate groups
Nucleic acids are linear polymers of nucleotide slinked 3’ hydroxyl to 5’ phosphate of the next nucleotide by
phosphodiester bonds
nuclear acids are
- RNA and DNA
sequence is always read
5’-3’
3’-5’ phosphodiester bonds
link nucleotides together to form polynucleotide chains
Noncovalent intramolecular bonds connect
complementary base pairs across double stranded stem
the antiparallel nature of the DNA double helix means that
the two chains have opposite orientations
ribosomal rna
the basis of structure and function of ribosomes
messenger rna
carries message for protein synthesis
transfer rna
carries the amino acid for protein synthesis
the double helix is stabilized by
hydrogen bonds
base pairs arise from
h-bonds : A-T, C-G
erwin chargaff
had the pairing data but didnt understand its implications
rosalind franklin
x-ray fiber diffraction data was key
Francis crick
recognized it was a helix with bases inside
James Watson
figured out h bonds using model building
jerry Donahue
knew the keto tautomer predominate at pH=7
product of dna
transcription
in prokaryotes
- a single mrna contain the information for synthesis of many proteins
in eukaryotes
a single mrna codes for just one protein but structure is composed of introns and exons
hnRNA
mixed introns and exons with polyA tail
intron
intervening sequence
exons
coding sequence
poly A tail
stability
____ produces final mRNA without introns
splicing
rRNA
serves as a scaffold for ribosomal proteins
genetic information in the
nucleotide sequence of mRNA is translated into the amino acid sequence of a polypeptide chain by ribosomes
tRNA
carries amino acid to the ribosome
3-‘ terminal sequence is CCA-3’-OH
the amino acid is attached in ester linkage to this 3’-OH
substrates of photosynthesis
amino acyl tRNA
2 differences between DNA and RNA
- dna contains 2-deoxyribose instead of ribose
- dna contains thymine instead of uracil
5-methyl group on thymine
labels it as a special kind of stabilized ‘uracil’ partner for A, protected from DNA repair enzymes
DNA lacking 2-OH’
is more stable
close or vicuna OH groups (2’ and 3’)
make RNA more susceptible to hydrolysis
nucleic acid fragments are separated by size using
electrophoresis
restriction enzymes
- ## nucleic acids being cut at specific sequences
DNA polymerase
generate DNA fragments that are randomly terminated
Types II and III restriction enzymes
cleave DNA chains at selected sites
an enzyme that requires a 6-base sequence is a
six-cutter
Type II restriction enzyme
- no ATP required
- recognition sites in double stranded DNA have a 2-fold symmetry
- 2- fold symmetry in a double stranded DNA site is a “palindromic site”
- cleavage can leave staggered or ‘sticky’ ends or can produce ‘blunt’ ends
nucleic acids are polyanions which are
attracted to the anode charge key characteristics of DNA synthesis
key characteristics of DNA synthesis
- 4 deoxynucleoside triphosphate and mg 2+ required
- a template strand is used to direct DNA synthesis
- a primer from which the new strand grows must be present
- many dna polymerases have nucleic activity that allows for the removal of mismatched bases
dNTPs
are considered to be active precursors because the subsequent breakdown of the released pyrophosphate helps to drive the phosphodiester bond formation
DNA polymerase catalyzes
phosphodiester-bridge formation
