DNA Replication and Gene Expression Quiz

DNA Replication and Gene Expression

• DNA Replication: A process where DNA is copied, crucial for cell division and maintaining genetic information.
• Eukaryotic Replication: Eukaryotes have multiple origins of replication on their chromosomes, in contrast to prokaryotes.
• Prokaryotic Replication: Uses one origin of replication.
• Leading Strand: Produced continuously in the 5' to 3' direction, following the replication fork.
• Lagging Strand: Synthesized discontinuously in short fragments (Okazaki fragments) moving away from the replication fork, and are joined by DNA ligase.
• DNA Polymerase: Enzyme that adds nucleotides during replication. It cannot start DNA synthesis independently and requires a primer.
• Telomerase: Enzyme that adds telomeric repeats to the ends of linear chromosomes, preventing loss of genetic material during replication.
• DNA Ligase: Enzyme that joins Okazaki fragments on the lagging strand.
• Single-stranded Binding Proteins: Maintain separate DNA strands for replication.
• Primase: Synthesizes RNA primers needed by DNA Polymerase for initiation.
• Helicase: Unwinds DNA double helix.
• Topoisomerases: Relieve the strain caused by unwinding of the double helix.

Gene Expression - Transcription and Translation

• Transcription: The process of using a DNA template to synthesize an RNA molecule, specifically mRNA.
• Initiation (Transcription): RNA polymerase binds to a promoter region on the DNA to begin transcription.
• Elongation (Transcription): RNA polymerase moves along the DNA template, synthesizing mRNA in the 5' to 3' direction.
• Termination (Transcription): RNA polymerase reaches a termination sequence, causing the release of the mRNA transcript.
• mRNA Processing (Eukaryotes only): Pre-mRNA undergoes processing with addition of a 5' cap and a poly-A tail, and splicing of introns to generate mature mRNA.
• Translation: The process of using mRNA to synthesize a polypeptide chain (protein).
• Ribosomes: Cellular structures where translation occurs.
• tRNA: Transfer RNA molecules that bring amino acids to the ribosome, matches to codons on the mRNA.
• Genetic Code: A set of rules that dictates which codons correspond to which amino acids.
• Codons (mRNA): Three-base sequences on mRNA that specify amino acids.
• Anticodons (tRNA): Three-base sequences on tRNA that are complementary to codons.
• Ribosomal Subunits: Two parts of Ribosomes (small and large) forming the complete ribosome.
• Initiation (Translation): The start codon on the mRNA binds to a ribosome
• Elongation (Translation): tRNA brings amino acids to the ribosome, and the ribosome forms peptide bonds.
• Termination (Translation): The stop codon on the mRNA signals the end of a polypeptide chain formation.

Genetic Mutations

• Point Mutation: A single base change.
• Missense Mutation: Changes a codon, resulting in a different amino acid.
• Nonsense Mutation: Changes a codon to a stop codon, leading to premature termination of translation.
• Silent Mutation: A codon change that does not affect the amino acid.
• Frameshift Mutation: Addition or deletion of a nucleotide, thereby shifting the reading frame of mRNA and producing an entirely different amino acid sequence that follows the alteration.
• Chromosomal Mutations: Major structural alterations in chromosomes, such as duplications, deletions, inversions, and translocations.

Other Key Terms

• Template Strand: The DNA strand used as a template for mRNA synthesis.
• Coding Strand: The DNA strand complementary to the template strand, same sequence as the RNA transcript, but contains uracil instead of thymine.