NUCLEOTIDES Flashcards
what 3 parts make up nucleotides
nitrogenous bases
pentose sugar
phosphate group
what is the pentose sugar in DNA called
deoxyribose
what is the pentose sugar in RNA called
ribose
diff between deoxyribose and ribose
ribose has one more O
what are the 4 bases in DNA
A T C G
A base
Adenine
T base
Thymine
C base
cytosine
G base
guanine
RNA bases
A U C G
U base
Uracil
What does U in RNA differ to in DNA
RNA = Uracil
DNA = Thymine
DNA complimentary bases
A - T
C - G
RNA complimentary bases
A - U
C - G
pyrimadines
thymine
cytosine
purines
adenine
guanine
difference in pyrimadines and purines
pyrimadines are made from one ring
purines are made from two rings
polynucleotides
many nucleotides bonded together by phosphodiester bonds between nuceotides
what reaction joins nucleotides together
condensation (+H2O)
what reaction breaks bonds between nucleotides
hydrolysis
DNA structure
- double helix structure
- 2 polynucleotide strands (nucleotides are held together by phosphodiester bonds)
- sugar-phosphate back bone on outside
- complimentary bases bonded in center (held together by hydrogen bonds)
- polynucleotides ae antiparallel (one runs from 5’ to 3’ but the other runs 3’ to 5’)
DNA and RNA differences
DNA found in chromosomes in nucleus but RNA found in cell cytoplasm
DNA nucleotide chain is longer than RNA
DNA is double strand but RNA is one strand
DNA has T base but RNA has U base
DNA has deoxyribose sugar but RNA has ribose sugar
DNA transcription
in nucleus:
DNA molecule unwinds using gyrase enzyme
H bonds between complementary base pairs break using DNA helicase enzyme to form replication fork
mRNA copy is made from the free template strand
the original DNA is bonded back together using DNA polymerase enzyme
mRNA leaves nucleus through nuclear pores
DNA translation
in cytoplasm:
mRNA attaches to ribosome (w rRNA)
tRNA from cytoplasm has complimentary amino acid anticodon to mRNA
ribosome moves along mRNA length, reading code
when two amino acids are agacent to each other a peptide bond forms
completed chain disassociates from ribosome
gyrase enzyme
unwinds double helix
DNA helicase enzyme
unzips two strands by breaking h bonds between bases
DNA ligase enzyme
seals sugar phosphate backbone in lagging strand
DNA polymerase enzyme
forms phosphodiester bonds
DNA replication
helicase unzips strands by breaking bases H bonds
DNA polymerase synthesises new strand
DNA replication completes
each new DNA molecule contains one old strand and one new strand
semi conservative replication
dna is made up of one old strand and one new strand (copy)
evidence for semi-conservative replication
messelson stahl experiment
using n-14 and n-15 to see density of dna of e.coli
centrifuge
results show one copy strand and one old strand of DNA
how many h bonds do a-t form
2
how many h bonds do c-g form
3
what was the conservative DNA theory
new DNA is both copied from old DNA as template
what was the dispersive DNA theory
DNA is a mixture of old and new nucleotides
DNA purification
place ethanol in freezer for 24hours
crush sample using mortar and pestle to disrupt membrane
mix detergent (breaks down membrane) and salt (clumps DNA) in water to make a lysis buffer
mix solution and sample in clean test tube aand heat at 60C for 5 min
add 3 drops of protease (breaks down histone proteins to uncoil DNA)
slowly pour chilled ethanol (shows as DNA is not soluble in alcohol) down side of tube
DNA forms at top of test tube
