Question & Answers 2023/2024
DNA replication correct answers ...must occur before cell can produce two genetically identical daughter
cell
Mutation correct answers ...can destroy organism if occurs in vital position within DNA
Mutation rate correct answers Rate at which changes occur in DNA sequences
Germ cells correct answers ...transmit genetic info from parent to offspring
Somatic cells correct answers ...form the body of an organism
DNA templating correct answers Mechanism cell uses to copy DNA sequence in one strand
complementary to another
DNA polymerase correct answers Nucleotide-polymerising enzyme
Deoxyribonucleoside triphosphates correct answers Free nucleotides that are substrates for DNA
polymerase
Replication fork correct answers Y-shaped region of replication that moves along DNA helix
DNA polymerases correct answers ...at replication forks can synthesise only in 5'-to-3' direction
Okazaki fragments correct answers Transient pieces of DNA at growing replication forks joined to DNA
after their synthesis
Leading strand correct answers DNA daughter strand synthesised continuously is known as the...
Lagging strand correct answers DNA daughter strand synthesised discontinuously is known as the...
Tautomers correct answers ...are constitutional isomers of organic compounds that readily interconvert
Helix geometry correct answers Small changes in...two hydrogen bonds form between G & T
Tautomeric correct answers ...forms mispair without change in helix geometry e.g. C & A
DNA polymerase correct answers Performs 1st proofreading just before nucleotide added to growing
chain
Exonucleolytic correct answers ...proofreading occurs immediately after incorrect nucleotide added to
chain
Primer strand correct answers DNA polymerase need previous 3'-OH end of a...to be able to elongate the
chain
, Primer correct answers DNA polymerase cannot start without a...
Strand-directed mismatch repair correct answers Cells can correct errors by a process of...(SDMR)
Primer correct answers The leading strand needs a...for start of replication
DNA primase correct answers Uses riboculeoside triphosphates to synthesise RNA primers on lagging
strand
RNA primer correct answers Okazaki synthesis ends when DNA polymerase runs into...at 5' end of
previous fragment
DNA ligase correct answers Joins 3' end of new Okazaki fragment to 5' end of previous one
DNA helicases correct answers Hydrolyse ATP, bound to single strand of DNA, needed to open helix
Single strand DNA binding correct answers ...proteins (AKA helix-destabilising proteins), bind single
strand without covering bases
Single strand DNA binding correct answers ...proteins aid helicase by stabilising single-strand
conformation
Single strand DNA binding correct answers ...proteins through cooperative binding, coat & straighten
lagging-strand template i.e. no hairpins
Sliding clamp correct answers Accessory protein (PCNA in eukaryotes), keeps polymerase on DNA when
moving
Clamp loader correct answers Hydrolyses protein to assemble sliding clamp around DNA
Mutator genes correct answers Alterations in...greatly increase rate of spontaneous mutations
Strand directed mismatch repair correct answers ...detects potential for distortion in helix from
noncomplementary base pairs
GTACs correct answers Unmethylated A residues on...allows new DNA strands to be distinguished from
old in E. coli
Single strand breaks correct answers New lagging strand contain...providing signals to direct mismatch
proofreading systems to strand
Hereditary nonpolyposis correct answers ...colon cancer (HNPCC) mutation on gene encoding in
mismatch proofreading
DNA topoisomerases correct answers Over winding in front of replication fork relieved by...
DNA topoisomerases correct answers Reversible nuclease, breaks phosphodiester bond in DNA