BIO 207 EXAM QUESTIONS WITH ANSWERS GRADED A+
2025/2026
✔✔Genome - ✔✔All genetic information that defines organism
✔✔Genes - ✔✔Contiguous packets of info enconded on chromosome
✔✔Structural gene - ✔✔Produces functional RNA, usually encodes protein
✔✔DNA control sequence - ✔✔Regulates expression of structural gene.
Does not encode RNA or protein
Includes promoters and binding sites for regulatory proteins
✔✔Plasmids - ✔✔Extrachromosomal DNA molecules physically separate from
chromosome.
Generally smaller than chromosome.
Contain additional genes for special circumstances and useful genes
Can replicate independent of chromosome.
Found in all three domains of life.
Usually circular but some linear.
Require host machinery for replication.
✔✔2 kinds of extragenomic DNA - ✔✔1. Plasmid
2. Genomes of bacteriophage
* Not mutually exclusive. Plasmid can be phage genome (prophage)
✔✔Plasmid advantage to cell - ✔✔Genes for resistance to antibiotics and toxins.
Genes for pathogenesis.
Symbiosis (genes providing other growth advantages).
✔✔Simpler the organism... - ✔✔Smaller its genome
✔✔Borrelia burgdorferi - ✔✔Cause of Lyme disease.
22 linear and circular plasmids and chromosomes (have both types)
✔✔Genomes of representative bacteria and archaea - ✔✔One circular chromosome.
Multiple chromosomes.
Combination of linear and circular chromosomes and plasmids.
Minimal genomes (kb range)
Massive genomes (mb range)
✔✔Bacterial and archaeal chromosome size range - ✔✔130 - 14,000 kilobase pairs (kb)
,✔✔Eukaryotic chromosome size range - ✔✔2,900 - over 100 million kb
✔✔Human genome size - ✔✔Over 3 million kb
✔✔Noncoding DNA - ✔✔>90% of eukaryotic genomes
<15% of prokaryotic genomes
✔✔Operon - ✔✔Where genes can exist in tandem with other genes
✔✔Monocystronic - ✔✔RNA produced from single gene
✔✔Polycystronic - ✔✔RNA produced from operon
✔✔DNA replication - ✔✔Most DNA replication is semiconservative and bidirectional.
Each daughter cell receives one parental and one newly synthesized strand
✔✔DnaA - ✔✔Initiator protein. Binds and melts OriC
✔✔DnaB - ✔✔Helicase. Unwinds DNA upstream of polymerase
✔✔DnaC - ✔✔Loads DnaB helicase ring onto ssDNA at melted OriC
✔✔DNA primase - ✔✔Synthesis of RNA primers
✔✔DNA Pol III - ✔✔Major replication enzyme
✔✔Sliding Clamp - ✔✔Prevents DNA Pol III from falling off template strand
✔✔Clamp Loader - ✔✔Carries 2 DNA Pol III enzymes and loads sliding clamp
✔✔DNA Pol I - ✔✔Replaces RNA primers with DNA
✔✔DNA gyrase - ✔✔Relieves positive supercoiling
✔✔SSBs - ✔✔Single-stranded binding proteins protect ssDNA yet to be replicated
✔✔Initiation (replication) - ✔✔Start of DNA replication is precisely timed and linked to
ratio of DNA to cell mass.
1. DnaA accumulates during growth, then triggers initiation (E.coli). DnaA-ATP proteins
bind to repeated 9-mer sequences within OriC.
2. Binding of DnaA leads to strand separation at 13-mer repeats.
3. Helicase (DnaB) and helicase loader (DnaC) assocaite with DnaA-bound origin.
, 4. Helicase loaders open helicase protein ring and place ring around ssDNA at origin.
Loading of helicase leads to release of helicase loader.
5. Helicase recruits DNA primase to make RNA primers on leading-strand templates.
Top-strand primer starts rightward replication; bottom-strand primer starts leftward
replication.
6. Clamp loaders carrying 2 DNA pol III load slinding clamp onto each leading-strand
DNA at RNA primer. Helicase-primase moves laterally at each fork to unwind DNA and
synthesize lagging-strand primers.
7. One DNA pol binds to clamp. Leading-strand synthesis begins at primer. New clamp
loaded on lagging-strand template, recruiting 2nd DNA pol for lagging-strand synthesis.
✔✔Elongation (replication) - ✔✔After initiation, 2 strands - leading and lagging.
Cell coordinates activity of 2 DNA pol III in one complex. 2 DNA pol III + DNA primase +
helicase = replisome
Replisome ensures that leading and lagging strands are synthesized simultaneously in
5' to 3' direction. Possible because lagging strand loops out after passing through its
polymerase.
✔✔Termination (replication) - ✔✔Tus (terminus utilization substance) binds to ter sites
and acts as counter-helicase. Multiple ter sites ensures that polymerase does not
escape and continue replicating DNA. Which ter site depends on which replication fork
lags behind the other.
Replication forms linked catenane of sister chromosomes.
Rings must be unlinked so that sister chromosomes can segregate after termination.
TopoIV recognizes dif sites on chromosomes and catalyzes cutting and rejoining steps
that pass one chromosome through another.
✔✔Catenane - ✔✔Pair of linked rings
✔✔Plasmid replication - ✔✔1. Bidirectional - starts at single origin and occurs in 2
directions simultaneously
2. Rolling-circle - Starts at single origin and moves in only one direction
Most plasmids use only one. A few can use either one, depending on sitatuon
✔✔Replicated genomes must segregate before... - ✔✔Cell division
✔✔High-copy-number - ✔✔Plasmids or chromosomes can segregate randomly to
daughter cells
✔✔Low-copy-number - ✔✔Plasmids or chromosomes must be actively segregate
equally to daughter cells
2025/2026
✔✔Genome - ✔✔All genetic information that defines organism
✔✔Genes - ✔✔Contiguous packets of info enconded on chromosome
✔✔Structural gene - ✔✔Produces functional RNA, usually encodes protein
✔✔DNA control sequence - ✔✔Regulates expression of structural gene.
Does not encode RNA or protein
Includes promoters and binding sites for regulatory proteins
✔✔Plasmids - ✔✔Extrachromosomal DNA molecules physically separate from
chromosome.
Generally smaller than chromosome.
Contain additional genes for special circumstances and useful genes
Can replicate independent of chromosome.
Found in all three domains of life.
Usually circular but some linear.
Require host machinery for replication.
✔✔2 kinds of extragenomic DNA - ✔✔1. Plasmid
2. Genomes of bacteriophage
* Not mutually exclusive. Plasmid can be phage genome (prophage)
✔✔Plasmid advantage to cell - ✔✔Genes for resistance to antibiotics and toxins.
Genes for pathogenesis.
Symbiosis (genes providing other growth advantages).
✔✔Simpler the organism... - ✔✔Smaller its genome
✔✔Borrelia burgdorferi - ✔✔Cause of Lyme disease.
22 linear and circular plasmids and chromosomes (have both types)
✔✔Genomes of representative bacteria and archaea - ✔✔One circular chromosome.
Multiple chromosomes.
Combination of linear and circular chromosomes and plasmids.
Minimal genomes (kb range)
Massive genomes (mb range)
✔✔Bacterial and archaeal chromosome size range - ✔✔130 - 14,000 kilobase pairs (kb)
,✔✔Eukaryotic chromosome size range - ✔✔2,900 - over 100 million kb
✔✔Human genome size - ✔✔Over 3 million kb
✔✔Noncoding DNA - ✔✔>90% of eukaryotic genomes
<15% of prokaryotic genomes
✔✔Operon - ✔✔Where genes can exist in tandem with other genes
✔✔Monocystronic - ✔✔RNA produced from single gene
✔✔Polycystronic - ✔✔RNA produced from operon
✔✔DNA replication - ✔✔Most DNA replication is semiconservative and bidirectional.
Each daughter cell receives one parental and one newly synthesized strand
✔✔DnaA - ✔✔Initiator protein. Binds and melts OriC
✔✔DnaB - ✔✔Helicase. Unwinds DNA upstream of polymerase
✔✔DnaC - ✔✔Loads DnaB helicase ring onto ssDNA at melted OriC
✔✔DNA primase - ✔✔Synthesis of RNA primers
✔✔DNA Pol III - ✔✔Major replication enzyme
✔✔Sliding Clamp - ✔✔Prevents DNA Pol III from falling off template strand
✔✔Clamp Loader - ✔✔Carries 2 DNA Pol III enzymes and loads sliding clamp
✔✔DNA Pol I - ✔✔Replaces RNA primers with DNA
✔✔DNA gyrase - ✔✔Relieves positive supercoiling
✔✔SSBs - ✔✔Single-stranded binding proteins protect ssDNA yet to be replicated
✔✔Initiation (replication) - ✔✔Start of DNA replication is precisely timed and linked to
ratio of DNA to cell mass.
1. DnaA accumulates during growth, then triggers initiation (E.coli). DnaA-ATP proteins
bind to repeated 9-mer sequences within OriC.
2. Binding of DnaA leads to strand separation at 13-mer repeats.
3. Helicase (DnaB) and helicase loader (DnaC) assocaite with DnaA-bound origin.
, 4. Helicase loaders open helicase protein ring and place ring around ssDNA at origin.
Loading of helicase leads to release of helicase loader.
5. Helicase recruits DNA primase to make RNA primers on leading-strand templates.
Top-strand primer starts rightward replication; bottom-strand primer starts leftward
replication.
6. Clamp loaders carrying 2 DNA pol III load slinding clamp onto each leading-strand
DNA at RNA primer. Helicase-primase moves laterally at each fork to unwind DNA and
synthesize lagging-strand primers.
7. One DNA pol binds to clamp. Leading-strand synthesis begins at primer. New clamp
loaded on lagging-strand template, recruiting 2nd DNA pol for lagging-strand synthesis.
✔✔Elongation (replication) - ✔✔After initiation, 2 strands - leading and lagging.
Cell coordinates activity of 2 DNA pol III in one complex. 2 DNA pol III + DNA primase +
helicase = replisome
Replisome ensures that leading and lagging strands are synthesized simultaneously in
5' to 3' direction. Possible because lagging strand loops out after passing through its
polymerase.
✔✔Termination (replication) - ✔✔Tus (terminus utilization substance) binds to ter sites
and acts as counter-helicase. Multiple ter sites ensures that polymerase does not
escape and continue replicating DNA. Which ter site depends on which replication fork
lags behind the other.
Replication forms linked catenane of sister chromosomes.
Rings must be unlinked so that sister chromosomes can segregate after termination.
TopoIV recognizes dif sites on chromosomes and catalyzes cutting and rejoining steps
that pass one chromosome through another.
✔✔Catenane - ✔✔Pair of linked rings
✔✔Plasmid replication - ✔✔1. Bidirectional - starts at single origin and occurs in 2
directions simultaneously
2. Rolling-circle - Starts at single origin and moves in only one direction
Most plasmids use only one. A few can use either one, depending on sitatuon
✔✔Replicated genomes must segregate before... - ✔✔Cell division
✔✔High-copy-number - ✔✔Plasmids or chromosomes can segregate randomly to
daughter cells
✔✔Low-copy-number - ✔✔Plasmids or chromosomes must be actively segregate
equally to daughter cells
