DNA Basics
The complete set of hereditary information in an organism.
Genome
This structure is a small circular DNA molecule found in bacteria.
plasmid
This enzyme unwinds and separates DNA strands.
Helicase
DNA polymerase can only add nucleotides in this direction
5' to 3'
These are repeating DNA sequences at chromosome ends
Telomeres
Different versions of the same gene that result in different traits.
Alleles
This process helps reduce the volume of prokaryotic DNA by twisting it.
supercoiling
The region where DNA strands separate during replication
Replication Fork
What is RNA primer?
Provides the starting point for DNA synthesis
This term describes the limit to how many times a cell can divide
The Hayflick limit
A scientist artificially increases the number of histones in a cell. Predict how this would affect gene expression and explain why.
Gene expression would likely decrease because more DNA would be tightly wrapped, making it less accessible for transcription.
Key difference in replication origins between prokaryotes and eukaryotes
One origin (prokaryotes) vs multiple origins (eukaryotes).
What is Topoisomerase?
An enzyme that relieves tension caused by DNA unwinding
The strand that is synthesized continuously
Leading Strand
Compare how telomere length would differ between skin cells and germ line cells, and explain why.
Skin cells shorten over time; germ cells maintain length due to telomerase.
Explain how histones contribute to DNA organization
They act as proteins DNA wraps around to compact and organize it.
Why do eukaryotic cells require multiple origins of replication?
Because their DNA is larger and more complex, so replication must occur faster.
What role do single-strand binding proteins (SSBs) play?
They prevent DNA strands from re-annealing.
What are Okazaki fragments?
These fragments are formed on the lagging strand
Explain why telomeres shorten during replication
The last RNA primer cannot be replaced, leaving a gap
A mutation affects how DNA wraps around histones. Predict one possible consequence.
Altered gene expression because DNA may be more or less accessible for transcription.
Predict what would happen if a eukaryotic chromosome had only one origin of replication
Replication would be too slow, possibly preventing proper cell division
What would happen if topoisomerase did not function properly during replication?
DNA would become overly twisted and tangled, stopping replication
A drug blocks RNA primase activity in rapidly dividing cells. Predict how this would affect DNA replication and explain why this might be useful in cancer treatment.
Replication would stop because DNA polymerase cannot start without primers. This could slow or stop cancer cell division.
Why are telomerase levels high in cancer cells?
To maintain telomeres and allow unlimited cell division