nucleic acids - created from Mind Map

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Describe the properties of nucleic acids

Describe the relationship between DNA, RNA and protein

Describe the structure of nucleotides

Explain giving examples how nucleotide analogues and antifolates function as chemotherapeutic and antiviral agents

List the structural properties of the Watson and Crick DNA right-handed double helix

Identify the base pairs that form in the DNA

Name the type of bonds that hold the base pairs toghether and explain their functional importance

Describe and original experiment that concluded that DNA was the carrier of genetic infromation

genetic info mustbe stored in a form that is managable in size and stable over a long period

genetic info must be decoded- transcription - nucleotide sequence is copied onto the RNA so that proteins can be translated

Info contained in the DNA / RNA must be accessible to proteins ad other nucleic acids

DNA is replicated so that the daughter cell receives the same copy

DNA sequences are always written as 5'- 3' orientation

COLLINEARITY : when amino acids sequences in the polypeptide corresponds to the codon sequences in the nucleaic acid

5 carbon chain sugar PENTOSE

phosphate group

Four nitrogenous bases

deoxyribose - no OH-

ribose - OH present

ARE ATTACHED TO THE 5'CARBON OF THE SUGAR

Purines (2 rings) : adenine & guanine

Pyramidines (1 ring) : thymine and cytosine and uracil

ARE ATTACHED TO THE 1'CARBON OF THE PENTOSE SUGAR BY A COVALENT BOND

Adenine has an NH2- group

guanine has a C=O and NH2- group

BOND AT 9 NITROGEN

uracil is very similar to cytosine

thymine has 2 C=O and CH3 groups

BOND AT 1 NITROGEN

uracil has =O

cytosine has NH2

ANTIMETABOLITES:ANALOGUES OF PURINE AND PYRAMIDINE BASES OR NUCLEOTIDES - ANTITUMOR, ANTIVIRAL AND ANTIMICROBIAL

6- MERCAPTOPURINE INHIBITS THE 1ST STEP OF THE PURINE SYNTHESIS

METHOTREXATE INHIBITS THE DIHYDROFOLATE REDUCTASE (HAS X1000 GREATER AFFINITY THAN HF2 - FOLATE ANALOGUE (ACTS AS A COMPETITIVE INHIBITOR

5-FLUROOURACIL INHIBITOR OF DNA SYSNTHESIS - FUra IS A PYRAMIDINE ANALOGUE OF URACIL

ACYCLOVIR IS A PURINE ANALOGUE IN THE HERPES VIRUS

AZT IN AIDS PATIENTS WHICH IS AN ANALOGUE TO THYMIDINE

since the cancer cells proliferate at a high rate - they are more sensitive to the inhibitors, as they require a larger number of nucleotides

Lethal dose of methatraxate is given and then the patient is 'rescued' by giving the 5-formylTHF or thymidine i.e the final product of the whole synthesis

if there is not enough dTMP, the DNA starts to utilise the dUMP(which is at a higher concentration but then the DNA is required to repair the DNA by the uracil gycoslase if there is not enough dTTP --> the DNA breaks down

5-fluorouracil is converted by normal metabolic enzymes to 5' -fluoro-2-deoxyuridine 5'-monophoasphate (FdUMP)

it is an irreversible inhibitor of the thymidylate synthase thus inhibits dTMP production

suicide substrates

adrucil, efudex, fluracil

DNA which contianes hepres encode deoxypyrimidine kinase - which phosphorylates purine analogues into their triphosphate --> thus incorporate into the DNA and prevents further synthesis of the DNA

AZT misses the OH- group thus does not allow further growth of the the DNA

the aids virus has an RNA genome which uses reverse transcriptase - n this stage AZT is incorporated into growing DNA chain as a thymidine analogue

two polynucleotide chains wound around each other in a right handed double helix

antiparallel chains - opposite polarity

sugar-phosphate backbones on the outside of the double helix and the the bases are oriented in the inside of the double helix

complimentary base pairs

0.34 nm apart in the DNA helix

10 base pairs per turn

grooves of unequal size, major and minor grooves

GUANINE AND CYTOSINE -> 3 H-BONDS

THYMINE/URACIL AND ARGANINE -> 2 H-BONDS

nucleotides are linked together by a covalent bond between the phosphate group (5') and the pentose sugar (3') - phosphodiester bonds

purine + pyramidine --> H-bonding

H-boding is relatively weak (TA - 2 &GC - 3)

complimentary base pairing

Friedrich Miesscher white blood cells with HCl to obtain nuclei for study, treated it with acid a precipitate containing C,H,O,N and P --> acidic