DNA Structure and Function

These flashcards cover key concepts about DNA structure, replication, transcription, translation, and genetic engineering.

DNA structure

DNA is made of two antiparallel polynucleotide strands twisted into a double helix with a sugar-phosphate backbone and nitrogen bases.

Complementary base pairing

A pairs with T, and C pairs with G in DNA.

Template strand

The DNA strand read by RNA polymerase to make a complementary RNA transcript.

Coding strand

The DNA strand that has the same base sequence as the RNA transcript, except T is replaced by U in RNA.

Directionality of nucleic acids

Nucleic acid strands have a 5′ end and a 3′ end, and are always synthesized in the 5′ → 3′ direction.

Universal genetic code

The same mRNA codons specify the same amino acids in almost all organisms.

Semi-conservative replication

DNA replication where each new DNA molecule contains one original strand and one newly synthesized strand.

DNA polymerase

Enzyme that synthesizes a new DNA strand complementary to the template strand in the 5′ → 3′ direction.

Eukaryotic DNA organization

Eukaryotic DNA is organized in multiple linear chromosomes and is housed within a nucleus.

Prokaryotic DNA organization

Prokaryotic DNA exists in a single circular chromosome located in the cytoplasm.

Difference between DNA and RNA

DNA is double-stranded and uses thymine; RNA is single-stranded and uses uracil instead.

Transcription

The process where RNA polymerase reads the DNA template and synthesizes RNA in the 5′ → 3′ direction.

Translation

The process where ribosomes read mRNA codons and synthesize polypeptides.

Codon

A three-base sequence on mRNA that specifies an amino acid.

Anticodon

A three-base sequence on tRNA that pairs with the corresponding mRNA codon.

Enzymes

Proteins that catalyze biochemical reactions by lowering the activation energy.

Competitive inhibitor

A molecule that competes with the substrate for the active site of an enzyme.

Non-competitive inhibitor

A molecule that binds to an enzyme at an allosteric site, changing its shape and reducing activity.

Mutation

A change in the DNA sequence that can affect protein structure or function.

PCR (Polymerase Chain Reaction)

A technique used to amplify a specific DNA sequence.

Gel electrophoresis

A method used to separate DNA fragments by size based on their movement through a gel.

Genetic engineering

The direct manipulation of an organism’s genes using biotechnology.

Transcription factors

Proteins that bind to DNA and regulate gene expression.