Nucleotides and Nucleic Acids Flashcards
Nucleotides
building blocks of nucleic acids
sugar, phosphate, base
DNA
stores and transmits info
gene
sections of dna that encode info to make products
mRNA
messenger RNA
carries info from the gene to the ribosome
tRNA
transfer RNA
translates info from mRNA into the amino acid code of the protein
rRNA
ribosomal RNA
carries out the synthesis of a protein
Functions of nucleotides
energy
enzyme cofactors
regulatory molecules
How many rings and nitrogens does a pyrimidine have?
one ring
2 nitrogens
How many rings and nitrogens does a purine have?
2 rings
4 nitrogens
nucleoside
sugar and a base
nucleobase
just the base
What are the 5 nucleoside bases?
cytosine
thymine
uracil
adenine
guanine
What does RNA do?
process info
What are the major structural differences between DNA and RNA?
- deoxy sugar at 2’ position
- bases used; U in RNA, T in DNA
How are DNA or RNA strands linked together?
phosphodiester backbone
How are genetic chains written and read?
5’ -> 3’
Nucleotides absorb UV light around?
260 nm
Nucleotides form hydrogens bonds with each other and are x, y, and z
aromatic
hydrophobic
planar
Minor bases
involved in regulation, methylation, or hydroxymethylation
inosine for tRNA
What is the primary structure of DNA?
the nucleotide sequence
What is the secondary structure of DNA?
double helix
What is the tertiary structure of DNA?
large 3D folding into chromosomes
Who was involved in the discovery of DNA structure?
James D. Watson
Francis Crick
Rosalind Franklin
Maurice Wilkins
A form
most stable in non aqueous environments; right handed helix
B form
most stable at physiological conditions; right handed helix
Z form
common in high GC repeat
used in regulation
left handed helix
DNA structure
double helix with antiparallel complementary strands
base pairs will cause an offset- results in major and minor grooves
What maintains the helix?
H bonding holds strands together
Pi stacking orients the bases
Palindromes
hairpins and cruciforms
mirrored repeats
used for regulation
Hoogsteen Pairing
H bonding to non-Watson and Crick sites
usually at low pH bc it requires protonation of cytosine
Triplex DNA
occurs in areas of only purine/pyrimidines
role in regulation and protein binding
Tetraplex
forms in areas of high G content
usually in telomeres
have a role in oncogenesis
RNA is
always single stranded
in a right handed helix
capable of forming hairpins and loops with itself
Denaturation
breaking of DNA into single strands
can be partial/total
no covalent bonds are broken
Annealing/ Renaturation
bringing the strands back together
What is more stable: DNA or RNA?
DNA
GC content
when higher leads to stronger bonds and ability to withstand higher temps
differs between species
useful for species identification in bacteria
DNA Hybridization
DNA with similar sequences will form hybrid duplexes
can help determine the function of genes
DNA damage
can lead to disease
caused by deamination, dimerization, chemical reactions, methylation
Deamination
oxidative, nucleotide transformation
Cytosine -> Uracil
most common deamination
responsible for high mutation rates
5-methylcytesine -> thymine
type of deamination
likely how thymine came to be evolutionarily
Adenosine -> hypoxanthine
Guanosine -> xanthine
types of less common deaminations
depurination
loss of the base from the sugar
causes an a basic site which can lead to errors in DNA processing
more common in DNA
bigger issue if it happens in RNA
dimerization
occurs because of UV radiation
requires repair
can lead to mutation
Nitrates and nitrites
common preservatives in body
convert to nitrous acid
Nitrous acid becomes nitrous amines which promote?
deamination
Enzymatic methylation
bases get methylated for a purpose
A is methylated for repair
about 5% of C is methylated as a marker in promoter regions and for gene regulation
DNA sequencing happens
automatically
