Module 8: V1 - V4 Flashcards
What is the structure of DNA?
double-helix
How does DNA encode information?
the balance between A=T and G=C pairs
Which biological processes involve DNA?
transcription, replication, recombination, repair and regulation
What biological processes is RNA involved in?
transcription, replication, translation, regulation and viruses
Which types of structures does RNA often form?
hairpins and loops
also complex 3D structures such as tRNA
What are nucleotides for?
components for RNA and DNA
used for energy storage e.g. ATP
cofactors in metabolism e.g. NAD+ and FAD+
Which nucleotides are purines?
nucleotides with a double-ring structure
Which nucleotides are pyrimidines?
nucleotides with a single-ring structure
What is the 5’ and 3’ end of DNA?
the 5’ end terminates at 5C and the 3’ end terminates at a phosphate group
Why is A always paired with T and G always paired with C?
this is because purines must always be matched up with pyrimidines
How many hydrogen bonds are there between A and T?
two
How many hydrogen bonds are there between G and C?
three
When does a cell replicate its DNA?
during the S (DNA synthesis) phase
What is DNA synthesised by?
DNA polymerases
What is the role of DNA polymerase III?
the main polymerase in DNA replication
What is the role of DNA polymerase I?
has functions in repair and recombination too
What allows the synthesis reaction of DNA to occur?
coordination of Mg2+ by aspartic acids
Mg2+ ions coordinate phosphate groups
DNA polymerases can only extend at the 3’ end
DNA polymerases need a double stranded section to start
Activity of which enzymes occurs in DNA polymerase I?
3’ -> 5’ exonuclease (proofreading) and 5’ -> 3’ exonuclease
Activity of which enzyme occurs in DNA polymerase III?
3’ -> 5’ exonuclease (proofreading)
What is the DUE section of the oriC sequence rich in?
AT base pairs
What is the role of DnaA protein?
recognises ori sequence; opens duplex at specific sites in origin
What is the role of DnaB protein (helicase)?
unwinds DNA
What is the role of primase (DnaG protein)?
synthesises RNA primers
What is the role of single-stranded DNA-binding protein (SSB)?
binds single-stranded DNA
What is the role of DNA gyrase (DNA topoisomerase II)?
relieves torsional strain generated by DNA unwinding
What are the major differences between RNA and DNA, both in their components and their overall structure?
RNA is ribonucleic acid while DNA is deoxyribonucleic acid as it contains a ribose which lacks one oxygen atom
RNA is single stranded while DNA is double stranded
RNA has uracil instead of thymine
What are nucleotides used for in the cell?
building blocks for the synthesis of DNA and RNA
also messengers and energy moving molecules
What would be different about the structure of DNA if the base pairing were between a purine and a purine, and a pyrimidine and a pyrimidine?
since the matching of purines to pyrimidines allows for constant width of DNA to be maintained, if purines were to bind to purines or if pyrimidines were to bind to pyrimidines, the width of DNA would vary
Explain how the mechanism of replication of DNA is immediately apparent from its structure.
the structure of DNA is what allows replication to occur as each parent strand is used as a template for the complimentary replicated strand
Why is it important that part of the sequence of the origin of replication is AT-rich?
because AT-rich regions of the origin prevent DNA strands from separating due to tension
How does a nucleic acid ‘recognise’ another nucleic acid? We will see this happen in many different processes, but one example would be a nucleotide entering the DNA polymerase during replication, and staying long enough for the phosphate backbone to be polymerised.
the key to recognition of specific nucleic acid sequences is base pairing between complementary strands of RNA or DNA
