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During DNA replication in eukaryotes, the lagging strand is synthesized discontinuously as Okazaki fragments. Which enzyme is primarily responsible for joining these fragments together after the removal of RNA primers?
DNA Polymerase I
DNA Polymerase III
DNA Primase
DNA Ligase
Certain mutations in the DNA polymerase delta gene can lead to reduced fidelity of DNA replication. Which of the following would be the MOST LIKELY direct consequence of such a mutation?
Decreased rate of Okazaki fragment synthesis
Inhibition of DNA unwinding by helicase
Increased rate of DNA repair mechanisms
Increased mutation rate in the newly synthesized DNA
Eukaryotic DNA replication is a complex process involving multiple proteins. Which of the following is NOT a function of Replication Protein A (RPA)?
Stabilizing single-stranded DNA
Preventing reannealing of separated DNA strands
Facilitating the binding of other replication proteins
Catalyzing the formation of phosphodiester bonds
Imagine a prokaryotic organism with a mutated DNA polymerase III that lacks 3' to 5' exonuclease activity. What would be the MOST LIKELY consequence of this mutation?
Slower replication fork movement
Inability to initiate DNA replication
A higher rate of mutations in the replicated DNA
Increased formation of Okazaki fragments
Telomerase activity is crucial for maintaining the length of telomeres. Which type of cells would you expect to have the HIGHEST telomerase activity?
Differentiated somatic cells
Senescent cells
Germ cells
Cells undergoing apoptosis
During DNA replication, topoisomerases play a crucial role. Which statement BEST describes the function of topoisomerases?
They synthesize RNA primers for DNA polymerase.
They unwind the DNA double helix at the replication fork.
They relieve torsional stress in the DNA helix ahead of the replication fork.
They join Okazaki fragments on the lagging strand.
The Human Genome Project revealed that the human genome contains approximately what percentage of coding sequences?
50%
25%
10%
Less than 2%
If the RNA world hypothesis is correct, which of the following would be the MOST likely scenario for the emergence of DNA?
DNA spontaneously arose independent of RNA and eventually outcompeted RNA.
Proteins evolved first and then catalyzed the formation of DNA from RNA.
RNA developed the ability to synthesize deoxyribonucleotides and polymerize them, eventually leading to DNA genomes.
Extraterrestrial DNA was introduced to Earth and replaced RNA.
The “RNA world” hypothesis proposes that RNA preceded DNA and proteins as the primary genetic material. A major challenge to this hypothesis is the relative instability of RNA compared to DNA. Why is RNA less stable?
RNA utilizes uracil instead of thymine.
RNA is typically single-stranded.
The 2'-OH group on the ribose sugar makes RNA susceptible to hydrolysis.
RNA is shorter than DNA.
Which of the following is NOT a component of a DNA nucleotide?
Deoxyribose sugar
Phosphate group
Nitrogenous base
Ribose sugar
