Nucleic Acids Flashcards
what are the 4 nitrogenous bases in DNA
cytosine
thymine
guanine
adenine
what are the 4 nitrogenous bases in RNA
cytosine
uracil
guanine
adenine
which nitrogenous DNA bases are purines
adenine and guanine
which nitrogenous DNA bases are pyrimidines
thymine and cytosine
how many rings do purines have
2
how many rings do pyrimidines have
1
what is the monomer of DNA
nucleotides
what do DNA nucleotides consist of
a nitrogenous base
a phosphate group
pentose deoxyribose sugar
what are the bonds involved in DNA
phosphodiester bonds
hydrogen bonds
where do phosphodiester bonds form in DNA
between phosphate group of one nucleotide and a sugar of the next which forms the sugar phosphate backbone.
DNA is …… stranded. The 2 strands are held together by …….. bonding between the ….. of the 2 strands
double
hydrogen
bases
A purine always pair with a ……….
pyrimidine
what are the complementary base pairs in DNA
thymine and adenine
cytosine and guanine
what is antiparallel
the two strands run parallel to eachother but in opposite directions
state 2 main types of nucleic acids
RNA- ribonucleic acid
DNA- deoxyribonucleic acid
nucleotide definition
monomers used to form nucleic acids
DNA strand definition
one of two polynucleotide chains that make up the double helix structure
state 3 main types of activity for which cells require energy
synthesis
transport
movement
2 similarities between ATP, DNA, RNA
-all have a pentose sugar in the middle
-all of them contain nitrogenous bases
2 differences between ATP, DNA, RNA
-DNA pentose sugar=deoxyribose, ATP and RNA= ribose
-ATP contains 3 phosphate groups per nucleotide, RNA and DNA contain 1 per nucleotide
Nucleic acid definition
chemical elements in them
large polymers formed from nucleotides
C H N P O
polymer definition
long-chain molecules composed of multiple bonded individual molecules (monomers) in a repeating pattern
double helix definition
two strands that wind around each other like a twisted ladder
outline structure of pyrimidines
smaller, contain single carbon ring structures
outline structure of purines
larger, contain double carbon ring structures
5 properties of ATP and why each makes it ideally suited to function as an energy transfer molecules
-small- moves easily into/out of and within cells
-water soluble- energy requiring processes happen in aq
-bonds between phosphates with intermediate energy- large enough to be useful for cellular reactions but not so large that energy is wasted as heat
-releases energy in small quantities- quantities are suitable to most cellular needs so energy is not lost as heat
-easily regenerated- can be recharged w energy
5 properties of ATP and why each makes it ideally suited to function as an energy transfer molecules
-small- moves easily into/out of and within cells
-water soluble- energy requiring processes happen in aq
-bonds between phosphates with intermediate energy- large enough to be useful for cellular reactions but not so large that energy is wasted as heat
-releases energy in small quantities- quantities are suitable to most cellular needs so energy is not lost as heat
-easily regenerated- can be recharged w energy
similarities and differences between nucleotides of DNA and RNA
components
RNA= a nitrogenous base and a ribose sugar and a phosphate group
DNA= deoxyribose sugar, nitrogenous base, phosphate group
DNA= deoxyribose sugar
RNA= ribose sugar
DNA= A T C G
RNA= A U C G
polynucleotide definition
polymer composed of 13 or more nucleotide monomers covalently bonded in a chain
complementary base pairing definition
specific hydrogen bonding between nitrogenous bases
monomer definition
individual molecules that make up a polymer
significance of double-stranded, complementary base paired nature of DNA for its function
allows to be copied and transcribed
this means the very large DNA molecule does not need to leave the nucleus in order for a cell to receive info for protein synthesis
why does a DNA molecule have equal amounts of adenine and thymine and cytosine and guanine
DNA is double stranded and has complementary base pairing
this therefore means that for every nitrogenous base there will be an equal amount of its complementary base pair present on the opposite strand
importance of the steps in the isolation and purification of DNA by precipitation
grind sample in mortar and pestle- breaks down cell walls
mix with detergent- breaks down cell membrane, releasing cell contents into sol
add salt- breaks the H bonds between DNA and water mol
add protease enzymes- break down proteins associated with DNA in nuclei
add layer of ice cold ethanol at 45 degree angle- causes DNA to precipitate
DNA will be seen as white strands forming between layer of sample and layer of alcohol.
why is sample grinded in DNA extraction
breaks down cell wall
why is detergent added in DNA extraction
breaks down cell membrane releasing contents into sol
why is salt added in DNA extraction
breaks hydrogen bonds between the DNA and water molecules
why is protease added in DNA extraction
break down the proteins associated with the DNA in nuclei
why is ethanol added in DNA extraction
alcohol causes DNA to precipitate
name of reaction that joins nucleotides
condensation
name of reaction that breaks phosphodiester bonds
hydrolysis
define sugar-phosphate backbone
forms structural framework of nucleic acids.
composed of alternating sugar and phosphate groups and defines directionality of the molecule.
define phosphorylation
addition of phosphate to an organic compound
significance of the sequence of bases in a DNA strand for its function
sequence carries the genetic info of an organism
3 consecutive bases code for a single amino acid
define universal code
refers to the fact that the same specific codons code for the same amino acids in all living organisms
process of transcription
- DNA uncoiled by DNA helicase
- RNA polymerase adds free complementary ribonucleotides to the template (antisense) strand
- sense strand (new) of DNA contains triplet code in correct order but is not transcribed
-antisense strand of DNA= complementary to the sense strand & is transcribed to make mRNA (copy of the sense strand) - condensation (phosphodiester) joins ribonucleotides to form mRNA
-mRNA separates from DNA and leaves nucleus through nuclear pores
transcription definition
process of copying sections of DNA base sequence to produce smaller molecules of mRNA which can be transported out of nucleus via nuclear pores to site of protein synthesis
structure of mRNA
-linear, single stranded molecule
-contains ribose
-contains bases A U G C
-carries codon sequence complementary to the sequence of the gene.
structure of tRNA
-single strand of RNA folded into clover leaf shape with 3 bases (anticodon) at one end of molecule
-contains ribose
-contains bases A U G C
-carries an anticodon which is complementary to the codon on mRNA
structure of tRNA
-single strand of RNA folded into clover leaf shape with 3 bases (anticodon) at one end of molecule
-contains ribose
-contains bases A U G C
-carries an anticodon which is complementary to the codon on mRNA
structure of DNA
-double stranded
-antiparallel
-double helix
-contains deoxyribose
-contains bases A T G C
- carries the original codon complementary to mRNA
function of mRNA
carries genetic information (amino acid sequence order) copied from DNA
function of tRNA
delivers correct amino acids to the ribosome in order to make up a polypeptide
function of DNA
carries the genetic material of an organism
how are polynucleotide strands made and broken down
condensation reaction between nucleotides form strong phosphodiester bonds (S-P backbone)
Hydrolysis reactions use a molecule of water to break these bonds
enzymes can catalyse these reactions
name complementary base pairs in RNA and DNA and n. H bonds
DNA= 2 H bonds between adenine and thymine
RNA= 2 H bonds between adenine and uracil
BOTH= 3 H bonds between cytosine and guanine
why is DNA replication described as semi conservative
strands from OG DNA molecule act as templates
new DNA consists of 1 new and 1 old strand
explain role of DNA helicase in semiconservative replication
breaks H bonds between base pairs and unzips to form 2 single strands which can act as a template
how is a new strand formed in SC replication
- free ribonucleotides from nucleoplasm/nuclear sap attach to exposed complementary bases
- DNA polymerase joins adjacent nucleotides on new strand in a 5-3 direction via condensation reaction to form phosphodiester bonds
- H bonds reform
identify 3 features of genetic code
non-overlapping (each triplet is only read once)
degenerate (more than one triplet codes for each amino acid)
universal (same bases and sequences used by all species)
how does a gene determine sequence of amino acids in a protein
consists of base triplets that code for specific amino acids
what does transcription produce
mRNA
where does transcription occur
nucleus
what happens after strand of mRNA is transcribed
- RNA polymerase detaches at terminal region
- H bonds reform, DNA recoils
- splicing removes introns from pre-mRNA in eukaryotes
- mRNA moves out via nuclear pore and attaches to ribosome (translation)
what does translation produce
proteins
where does translation occur
in cytoplasm on ribosomes
outline translation
- ribosome moves along mRNA until start codon
- tRNA anticodon attaches to comp codon on mRNA
- condensation R forms peptide bonds between amino acids on tRNA
(requires energy ATP from hydrolysis) - process continues to form polypeptide chain until stop reached
describe structure of ATP and ADP
nucleotide derivative of adenine
ATP has 3 inorganic phosphate groups
ADP has 2
what is a mutation
alteration to DNA base sequence, often arise spontaneously during DNA replication
