DLA 7 Structure And Function Of Nucleic Acids Flashcards
What are the designations to describe the structure of DNA and RNA?
Primary structure: the sequence of bases along the polynucleotide chain
Secondary structure: the 3D structure. Eg doubke gelid of DNA
Tertiary structure: includes Supercoiling of the secondary structure
Quart entry: the interaction of nucleic acids with proteins
Contrast the 3 main types of rRNA
mRNA
- linear single stranded molecule
- carries codon information for translation
- post transcriptionally modified- 2% of total RNA
tRNA
- folded stem loop structures formed by intra molecular H-bonding
- carries amino acid to ribosome
- 16% of total RNA
rRNA
- linear single stranded, folded molecule
- complexes with protein to form ribosome
- 82% of total RNA
What are the catalytic activity of rRNA?
Forming covalent peptide bonds
What are snRNA?
- Involved in generation of mature mRNA transcripts
- Central components of the splicing apparatus that removes non-coding introns and joints together protein coding exons
Vertebrates snRNA- U1, U2, U3, U4, U5 & U6. Short in length between 106-185 nucleotides
Associate with specific proteins to form Small nuclear ribonucleoproteins
Differentiate nucleoside and nucleotides
Nucleoside- base + sugar
Nucleotide- base+ sugar+ phosphate
Contrast pyrimidines and purines
Pyrimidines- heterocyclic compounds containing nitrogen atoms at position 1 and 3 of a 6-member ring. Pyrimidines include thymine, cytosine and guanine
Purine- heterocyclic compounds consisting of a pyrimidine fuse to a 5 member imidazole ring. Purines include adenine and guanine
What are the functions of nucleoside triphosphate?
ATP- universal chemical energy of biological systems
GTP- energy source for protein biosynthesis and involved in signal transduction
UTP-activation of sugars in biosynthesis of CHO and glycoprotein
CTP- activation of reactants in phospholipids biosynthesis
Nucleotide derivatives functions as enzymes eg. Pyridine and flavin enzymes
How is azidothymine and didadenosine used clinically?
These are both nucleosides that lack a free 3’ OH group. These drugs have high affinity for reverse transcriptase enzyme and inhibit their activity. They are therefore used in treatment of retro-viral infections such as HIV
How does acyclovir function clinically ?
Posses an open chain structure in place of the pentose sugar ring structure. Acyclovir is a potent inhibitor of viral DNA polymerase and causes termination of DNA replication. It is used in treatment of herpes virus
How does tenofovir work clinically?
A nucleotide analog that possess an open chain structure in place of the pentose sugar ring structure. Tenofovir is a potent reverse transcriptase inhibitor that is used to treat HIV infection.
How doncytosine /adenosine arabinoside function clinically?
Possess unusual planar structures and as a result inhibit the activity of DNA polymerase as well as inducing DNA damage by incorporation into a DNA during replication. These drugs are used as anti cancer drugs by selectively destroying the rapidly dividing cancer cells
How do cytidine analogs function clinically?
The cytidine analogs 5-aza-2’-deoxycytidine and 5-azacytidine disrupt the Epigenetic process of DNA methylation. These analogs possess a N atom at position 5 of cytidine and therefore prevent the DNA methyl-transferase enzymes from methylation cytosine at position 5. In addition, they have been found to be direct inhibitors of DNA methyl-transferase enzymes. DNA methylation is an important mechanism of gene regulation (transcription) in eukaryotes
How does 5-fluorouracil function?
An anti cancer agent. In cells it is converted to FdUMP which inhibits thymidylate kinase, and thus inhibiting synthesis of thymine nucleotides that are required for DNA synthesis
How does Azathioprine function clinically?
Metabolized to 6-mercaptopurine which suppresses ejection during organ transplantation
How does Allopurinol function clinically?
A treatment for gout. It inhibits xanthine oxidase, thus lowering the conversion of purine bases to uric acid end products. The purines are excreted as xanthine and hypoxanthineehich are more soluble than uric acid.
