Discuss the structure and function of nucleic acids including DNA and RNA. Flashcards
Nucleic Acids: Define, give the two classes (include the flow chart) and give the functions of each nucleic acid
- Macromolecules - contain genetic info and enable protein synthesis
- Functions:
- DNA:
- Storage
- Directs replications
- Directs transcription
- mRNA:
- Directs translation (carrier)
- tRNA:
- Deliver AA (translator)
- rRNA:
- Components of ribosomes that have structual and functional roles
- DNA:
What are the three components of nucleic acids (general - DNA and RNA)
- 5 carbon pentose sugar
- Nitrogen containing organic base
- Phosphate group
What are the pentose sugars for DNA and RNA and what is the only difference between the 2 molecules?
- Deoxyribose (DNA)
- Ribose (RNA)
- Deoxyrbiose is missing the -OH group at 2’
Nitrogen containing organic base: Name and define the 2 families and put each base according to its correct family
- Pyrimidine - Single carbon-nitrogen ring, 2 nitrigen atoms
- Cytosine
- Thymine - DNA ONLY
- Uracil - RNA only
- Pyrmadine - Double carbon-nitrogen ring, 4 nitrogen atoms
- Adenine
- Guanine
Define: Nucleoside and Nucleotide
- Nucleoside = Base + 5-carbon sugar
- Nucleotide = Phosphorylated nucleoside (5’-position)
What is a phosphodiester bond (DNA and RNA) and what does it form as a result?
- Link between 3’ carbon atom of one sugar and 5’ carbon of another.
- Sugar- phosphate backbone
Base Pairing: Occurs in….only, give its purpose, give the two types and distance between both base pairs and why
- DNA
- To maintain regular heliacal structure
- A+T (2 HBs)
- G+C (3HBs)
- 1.085nm - purine + pyramidine
Give 2 general features on the structure of DNA (I.E what does it look like by simply looking at it)
- 2 strands twisted around each other = double helix
- Anti-parallel - ‘3 to 5’ ‘5 to 3’
What are the two types of grooves
- Major groove - Open (backbones further apart)
- Minor groove - Constricted (backbones closer together)
Describe the steps involved in semi-conservative replication:
- DNA helicase unwinds/seperates the DNA (at replication fork)
- DNA primase synthesises RNA primers
- Free floating nucleotides bind to each strand (via CBP)
- DNA polymerase binds to 3’ end of primer and joins nucleotides in a ‘5 to 3’ direction
- Leading strand: DNA polymerase moves towards repilcation fork and synthesises continitously = 1 primer
- Lagging strand: DNA polymerase moves away from replication fork and synthesises in pieces (Okazaki fragments) = mulitple primers
- DNA pol I removes RNA primers and replaces with DNA nucleotides
- DNA pol II has proofreading exonuclease activity = corrects mismacthes
- DNA ligase joins Okazaki fragments
Antiretorviral agents: Give 3 examples, what their main function is, why they work and give the mechanism of action (image)
- Zidovudine, Lamivudine, Zalcitabine
- Reduce viral load
- No ‘OH group on the 3’ pentose sugar
What are the major differences between RNA and DNA?
- Single stranded
- A-U
- Ribose sugar
- Extensive secondary structure and intramolecular double-stranded regions
What are the three types of DNA polymerase and what does each transcribe?
- RNA pol 1 - rRNA
- RNA pol 2 - mRNA
- RNA pol 3 - tRNA
Define the process of transcription?
- Process DNA is copied into RNA
Give the steps involved in transcription (initation, elongation and terminiation)
- Initation:
- RNA pol binds to promter and unwinds DNA (topoisomerases I and II)
- 1 strand = template
- Elongation:
- Ribonucleotides bind to template strand (via CBP)
- RNA pol binds joins the ribonucleotides via phosphodiester bond (5’–>3’)
- Termination:
- RNA pol binds to stop = transcription stops
- RNA and RNA pol deattach
- DNA unwinds
