DNA Replication Basics
During which specific phase of the cell cycle is the entire genome duplicated in preparation for mitosis?
S-Phase
Which enzyme disrupts hydrogen bonds between base pairs to open the replication fork?
Helicase
What process uses a DNA template to generate a complementary RNA strand?
Transcription
How many copies of each gene does a haploid cell contain?
One
What mutation involves a single nucleotide change in the DNA sequence?
Point mutation
Before replication begins, what essential structural change must occur between the two complementary DNA strands?
The strands must unwind and seperate
Which proteins stabilize unwound DNA by preventing the separated strands from reannealing?
Single strand binding proteins (SSBPs)
What is the term for a three-nucleotide sequence on mRNA that specifies a particular amino acid?
A codon
In human somatic cells, how many chromosomes are present in a normal diploid genome?
46 chromosomes
Which mutation type converts a codon into a premature stop codon, producing a truncated protein?
Nonsense mutation
What model of DNA replication states that each daughter molecule contains one parental strand and one newly synthesized strand?
Semi-Conservative Model
What name is given to the DNA strand that is synthesized continuously in the direction of the replication fork?
The leading strand.
During translation initiation, which ribosomal site does the first tRNA—carrying methionine—bind to?
P Site
What proteins do eukaryotic DNA wrap around to form nucleosomes and facilitate chromatin organization?
Histones
Adding or removing a nucleotide results in what type of mutation that alters the reading frame of an mRNA sequence?
Which pair of researchers experimentally validated the correct model of DNA replication using nitrogen isotopes (N-15/N-14)?
Nelson and Stahl
What are the short, discontinuously synthesized DNA fragments formed on the lagging strand?
Okazaki fragments
In eukaryotic cells, spliceosomes remove which non-coding sequences from pre-mRNA?
Introns
What term describes the small circular DNA molecules found in prokaryotes that often carry accessory genes?
Plasmids
What chromosomal mutation occurs when a segment breaks off, rotates 180°, and reattaches?
An inversion mutation
Which enzyme prevents overwinding and reduces torsional stress ahead of the replication fork by creating temporary breaks in the DNA?
Topoisomerase II
Which enzyme removes RNA primers and replaces them with DNA nucleotides during replication?
DNA Polymerase I
Translation terminates when the ribosome encounters which specific type of codons?
Stop codons (UAA, UAG, UGA).
What is the name for the higher-order twisting and compaction of DNA beyond the nucleosome level?
Supercoiling
Sickle cell anemia is caused by which specific type of point mutation that substitutes one amino acid for another?
A missense mutation.