Introduction to Molecular Biology – Lecture 1

Vocabulary flashcards covering key terms and definitions from Lecture 1 on molecular biology, including DNA structure, special DNA sequences, denaturation/renaturation phenomena, and applications such as PCR and hybridization assays.

Nucleic Acid

Polymer of nucleotides (DNA or RNA) that stores and transmits genetic information.

DNA (Deoxyribonucleic Acid)

Double-stranded nucleic acid containing deoxyribose; primary hereditary material of cells.

RNA (Ribonucleic Acid)

Single- or double-stranded nucleic acid containing ribose; copies and translates genetic instructions into proteins.

Central Dogma of Molecular Biology

Concept that genetic information flows from DNA → RNA → protein.

Nucleotide

Monomer of nucleic acids composed of a nitrogenous base, a pentose sugar, and one or more phosphate groups.

Nucleoside

Nitrogenous base attached to a pentose sugar, lacking phosphate.

Nitrogenous Base

Adenine, guanine, cytosine, thymine (DNA) or uracil (RNA); component of nucleotides responsible for base pairing.

Pentose Sugar

Five-carbon sugar (ribose in RNA, deoxyribose in DNA) in nucleotides.

Phosphate Group

One or more phosphates that link nucleotides via phosphodiester bonds and give nucleic acids their negative charge.

Double Helix

Right-handed, two-stranded helical structure of DNA discovered by Watson and Crick in 1953.

Antiparallel

Orientation in which the two DNA strands run in opposite 5′→3′ directions.

Mirror Repeat

Symmetric DNA sequence repeated on the same strand; superimposed by 180° rotation about the vertical axis.

Palindrome (DNA)

Sequence whose complementary strand reads the same in the opposite direction, exhibiting twofold symmetry.

Hairpin

Secondary structure formed when a single DNA or RNA strand with a palindromic region folds back on itself.

Cruciform

Cross-shaped structure formed when both strands of duplex DNA create paired hairpins at a palindromic site.

Hydrogen Bonds (Base Pairing)

Non-covalent interactions that hold complementary bases (A–T, G–C) together in the DNA helix.

Base Stacking

Hydrophobic interactions between adjacent bases that provide major stabilizing energy to the DNA helix.

Denaturation (DNA)

Separation of double-stranded DNA into single strands by heat or extreme pH without breaking covalent bonds.

Renaturation / Annealing

Re-formation of double-stranded DNA when denaturing conditions are removed.

Hypochromic Effect

Decrease in UV absorbance at 260 nm when bases are stacked or paired in double-stranded nucleic acids.

Hyperchromic Effect

Increase in UV absorbance at 260 nm when DNA is denatured, reflecting unstacked, unpaired bases.

Melting Temperature (Tm)

Temperature at which half of a DNA sample is single-stranded; characteristic for each DNA species.

GC Content

Proportion of guanine-cytosine base pairs in DNA; higher GC → higher Tm due to three hydrogen bonds per pair.

A-T Rich Bubble

Local unwound region that forms preferentially in DNA segments rich in A–T pairs, visible under partial denaturation.

Hybridization

Formation of duplex DNA by pairing complementary strands from different sources or species.

PCR (Polymerase Chain Reaction)

Technique that amplifies specific DNA sequences through repeated cycles of denaturation, annealing, and extension.

Southern Blot

Method that detects specific DNA fragments via transfer to a membrane and hybridization with a labeled probe.

Dot Blot

Simplified hybridization assay where DNA samples are spotted on a membrane and probed for target sequences.

GISH (Genomic In Situ Hybridization)

Cytogenetic technique using whole genomic probes to visualize chromosomal origins and evolutionary relationships.

Watson, Crick & Wilkins (1962 Nobel Prize)

Scientists recognized for elucidating the double-helical structure of DNA.