Chapter 7: DNA Structure, Function, Gene Expression, and Molecular Biology

Comprehensive vocabulary flashcards covering DNA structure, chromosomal organization, replication, mutations, gene expression, transcription, translation, post-translational modifications, and viral/prion biology.

Histones

Proteins around which DNA is wrapped to form chromosomes.

Purines

Nitrogenous bases containing a double-ring structure, consisting of adenine and guanine.

Pyrimidines

Nitrogenous bases containing a single-ring structure, consisting of cytosine and thymine in DNA.

Autosomes

The numbered chromosome pairs 1 through 22 in humans that are identical in both biological sexes and are not sex chromosomes.

Sex chromosomes

Chromosome pair 23 in humans (X and Y) that determines biological sex; unlike autosomes, X and Y are not homologous to each other.

Karyotype

An organized visual display or profile of an individual's complete set of paired chromosomes.

Gene

A specific segment of DNA that contains the instructions on how to build a protein.

Homologous chromosomes

Chromosome pairs that are the same size and carry the same genes, existing as pairs for chromosomes 1 through 22.

Semi-conservative replication

The mechanism of DNA replication in which each newly formed DNA double helix is composed of one conserved original strand and one newly synthesized strand.

DNA polymerase

The enzyme that adds complementary nucleotides during DNA replication and proofreads each new nucleotide, reducing the replication error rate from 1 error per 100,000 base pairs to 1 error per 1 billion base pairs.

Mutation

Any error or alteration to the original DNA sequence, which can produce beneficial, harmful, or neutral effects.

Point mutation

A DNA mutation involving a change in nucleotide sequence without an alteration in the overall length of the sequence.

Chromosomal translocation

A large-scale chromosomal mutation where a segment of one chromosome breaks off and attaches to a non-homologous chromosome.

Chromosomal inversion

A large-scale chromosomal mutation in which a segment of a chromosome breaks off, flips in orientation, and reattaches within the same chromosome.

Central Dogma of Biology

The principle describing the flow of genetic information: DNA is transcribed into RNA in the nucleus, which is then translated into protein in the cytoplasm.

Transcription

The synthesis of an RNA molecule from a DNA template strand, performed in the nucleus of eukaryotic cells by RNA polymerase.

Promoter

A specific sequence of DNA to which RNA polymerase must bind to initiate transcription.

Splicing

The RNA processing step that removes non-coding introns from pre-mRNA and joins coding exons together to form mature mRNA.

Translation

The process occurring in the cytoplasm or associated with the rough endoplasmic reticulum where ribosomes read mRNA codons to synthesize a polypeptide chain.

Codon

A sequence of three consecutive nucleotides in mRNA that specifies a particular amino acid or signals the termination of translation.

Transfer RNA (tRNA)

A specialized RNA molecule that carries a specific amino acid to the ribosome and pairs its anticodon with the complementary codon on mRNA.

Anticodon

A three-base sequence located on a tRNA molecule that base-pairs with a complementary three-base codon on an mRNA strand.

A-site (Arrive site)

The site on the ribosome where a newly arriving tRNA carrying an amino acid enters and matches its anticodon to the mRNA codon.

P-site (Peptide site)

The ribosomal binding site that holds the tRNA carrying the growing polypeptide chain.

E-site (Exit site)

The site on the ribosome where the uncharged (empty) tRNA moves before being released and exiting the ribosome.

Genetic code redundancy

The property of the genetic code where 64 possible triplet codons code for only 20 amino acids, helping protect against point mutations and transcription errors.

Release factor

A protein that binds to a stop codon (UAA, UAG, or UGA) in the ribosomal A-site, causing the completed peptide chain to be released and ending translation.

Polysome

A structure consisting of multiple ribosomes simultaneously translating a single mRNA molecule.

Lac operon

A bacterial operon regulated by a repressor protein; it is normally in the 'OFF' position blocking RNA polymerase, but turns 'ON' when lactose binds to the repressor, allowing gene transcription.

Post-translational modification (PTM)

Chemical modifications made to a protein after its synthesis that regulate its function, cellular localization, activation, interactions, and degradation.

Proteolytic processing

A post-translational mechanism in which a specific section of a protein is cleaved off, inducing a conformational change that activates the protein.

Phosphorylation

A reversible post-translational modification involving the addition of a phosphate group to alter a protein's activity or its interactions with other proteins or DNA.

Virion

A complete, infective viral particle consisting of genetic material (DNA or RNA) enclosed within a protective protein coat.

Lytic pathway

A viral infection pathway where the host cell manufactures viral proteins and viral DNA to assemble new virions, culminating in host cell lysis to release them.

Lysogenic pathway

A viral infection pathway in which viral DNA integrates into the host chromosome as a prophage, replicating passively as the host cell divides without killing the host.

Prophage

The latent form of a bacteriophage genome that has been inserted and integrated into the circular bacterial host chromosome.

Reverse transcriptase

A viral enzyme utilized by retroviruses such as HIV to synthesize double-stranded DNA from a single-stranded viral RNA template.

Prion

A proteinaceous infectious particle with an abnormal shape that propagates infection by altering the conformation of normal proteins rather than using nucleic acids.