Exam 2

Frederick Griffith’s Experiment (1928)

Demonstrated transformation in bacteria, showing that a 'transforming principle' could transfer genetic information.

Avery, MacLeod, and McCarty Experiment (1944)

Identified DNA as the 'transforming principle' by proving that DNA alone caused transformation.

Hershey-Chase Experiment (1952)

Demonstrated that DNA, not protein, is the genetic material transferred to bacteria using bacteriophages labeled with radioactive phosphorus and sulfur.

Meselson-Stahl Experiment (1958)

Showed that DNA replicates semiconservatively using nitrogen isotopes (15N & 14N) to trace the density of DNA strands.

Components of DNA

Nucleotides consist of a nitrogenous base (A, T, C, G), deoxyribose sugar, and phosphate group.

Chargaff’s Rules

In DNA, the amount of adenine equals thymine (A = T) and the amount of cytosine equals guanine (C = G).

Double Helix Model

Describes the structure of DNA, as discovered by Watson and Crick, which is antiparallel and stabilized by hydrogen bonds.

Key Enzymes in DNA Replication

Helicase unzips the DNA strands, SSBPs stabilize unwound DNA, Primase synthesizes RNA primers, and DNA polymerases synthesize DNA.

Leading vs. Lagging Strand

Leading strand is synthesized continuously, while the lagging strand is synthesized discontinuously via Okazaki fragments.

Telomerase

Enzyme that extends telomeres to prevent DNA loss at chromosome ends during replication, linked to cancer cell immortality.

Polymerase Chain Reaction (PCR)

Technique to amplify DNA through cycles of denaturation, annealing, and extension.

Sanger Sequencing

Method that uses dideoxynucleotides (ddNTPs) to terminate DNA replication for sequencing.

Next-Generation Sequencing (NGS)

Advanced sequencing method that allows simultaneous sequencing of millions of DNA fragments.

Restriction Enzymes

Cut DNA at specific palindromic sequences, creating sticky or blunt ends for cloning.

Plasmid Features

Plasmids contain origin of replication (ORI), selectable markers, and multiple cloning sites (MCS) for gene cloning.

CRISPR-Cas9

Gene editing technology that uses guide RNA to target DNA sequences and Cas9 to cut DNA for modifications.

Alternative Splicing

Process that produces multiple protein forms from one gene, increasing genetic diversity.

Translation Process

Synthesis of proteins from mRNA involving initiation, elongation, and termination stages.

Frameshift Mutation

Mutation caused by insertions or deletions that shift the reading frame, often leading to nonfunctional proteins.

Signal Sequences

Short peptide sequences that direct proteins to specific locations within the cell.