Molecular Genetics: DNA Structure, Protein Synthesis, Mutations, Profiling, and Antibiotics

Vocabulary practice flashcards covering the structure and discovery of DNA, transcription and translation, genetic mutations, DNA profiling, and antibiotic mechanisms of protein synthesis inhibition.

Nucleic Acids

Organic molecules (DNA and RNA) that store information controlling cellular activity and organism development by regulating protein synthesis.

X-ray Crystallography

The scientific method initiated by Maurice Wilkins and Rosalind Franklin to analyze diffraction patterns and discover the helical structure of DNA.

1962 Nobel Prize in Physiology or Medicine

The prize awarded to James Watson, Francis Crick, and Maurice Wilkins as living recipients for discovering the double helix structure of DNA.

Rosalind Franklin

The researcher whose X-ray diffraction patterns revealed evidence of DNA's helical structure before her death, which Watson and Crick analyzed to construct their model.

Triplet Code

The genetic coding rule established in 1961 by Crick and Brenner showing that three nitrogenous bases in DNA code for a specific amino acid.

Nucleotide

The monomer of nucleic acids, consisting of a phosphate molecule, a pentose sugar (deoxyribose in DNA or ribose in RNA), and a nitrogenous base.

Double Helix

The coiled, twisted-ladder structure of DNA consisting of two outer chains of alternating sugar-phosphate links joined by strong bonds and inner rungs of paired nitrogenous bases joined by weak hydrogen bonds.

Complementary Base Pairing

The pairing rule in nucleic acids where adenine pairs with thymine (or uracil in RNA) via 2 hydrogen bonds, and cytosine pairs with guanine via 3 hydrogen bonds.

Purines

Nitrogenous bases characterized by two fused rings of carbon, nitrogen, and hydrogen atoms; specifically adenine and guanine.

Pyrimidines

Smaller nitrogenous bases characterized by a single ring structure; specifically cytosine, thymine, and uracil.

Role of DNA (deoxyribonucleic acid)

1. Carry hereditary info (as genes)

2. codes for protein synthesis

3. replicates = genetic info passed to daughter cell (gen to gen)

Non-coding DNA

Regions of DNA that do not code for proteins, constituting approximately $98\%$ of complex organism DNA and functioning to form functional RNA molecules.

Exons and Introns

Exons are protein-coding regions of DNA, whereas introns are intervening non-coding regions that interrupt them.

Salt Method

A simple, time-saving biological technique used to extract and isolate DNA molecules from biological material while minimizing degradation.

Ribonucleic Acid (RNA)

A single-stranded nucleic acid containing ribose sugar and uracil instead of thymine that carries instructions from nuclear DNA to ribosomes in the cytoplasm.

Mitochondrial DNA (mtDNA)

DNA located inside mitochondria that is passed down exclusively through egg cell cytoplasm across generations, tracing direct maternal lineages.

Marker Site (mtDNA)

A site where a nucleotide replacement or mutation occurs in mitochondrial DNA, used to build profiles and determine close relations along female lineages.

Transcription

The stage of protein synthesis in the nucleus where RNA polymerase unwinds DNA, separates its strands, and joins complementary RNA nucleotides into an mRNA molecule.

RNA Polymerase

The enzyme that attaches to the DNA template strand, unzips the double helix by breaking nucleotide hydrogen bonds, and builds the mRNA sugar-phosphate backbone.

Codon

A genetic codeword consisting of three consecutive nitrogenous bases on an mRNA molecule that directs the placement of a specific amino acid.

Transfer RNA (tRNA)

A type of RNA possessing a three-base anticodon that binds to a specific amino acid in the cytoplasm and transports it to the matching codon on the ribosome.

Translation

The process in the cytoplasm where ribosomes read mRNA codons and pair them with complementary tRNA anticodons to link amino acids via peptide bonds.

Ribosomal RNA (rRNA)

RNA that combines with proteins to form ribosomes, moving codon to codon along mRNA to direct and control protein synthesis.

Mutations

Alterations in genetic make-up resulting from damaged or lost nucleotides during crossing over, DNA replication, transcription, or mutagen exposure.

Mutagen

Physical or chemical agents—including sunlight, radiation, mutagenic chemicals, viruses, and microorganisms—that induce or accelerate DNA mutations.

Point Mutation

A localized gene mutation involving a structural alteration to a single nucleotide in a DNA strand.

Substitution Mutation

A gene mutation in which one nucleotide in a DNA molecule is exchanged for another, altering mRNA codons and resulting protein synthesis.

Insertion and Deletion

Gene mutations where one or more extra nucleotides are added to (insertion) or removed from (deletion) a DNA molecule.

DNA profiling

Identifying regions of a persons DNA

Short Tandem Repeats (STRs)

Repeating sequences of base pairs located at specific points in non-coding DNA whose number of repeats varies among different individuals.

Restriction Enzymes

Enzymes utilized in DNA profiling to cut DNA strands at the beginning and end of repeated base pair sequences, producing fragments of varied lengths.

Polymerase Chain Reaction (PCR)

A molecular technique used to make multiple copies of a targeted DNA segment, producing sufficient fragments for profiling analysis.

Gel Electrophoresis

A laboratory procedure used in DNA profiling to separate DNA fragments according to size, yielding a distinct pattern of dark bands.

DNA Fingerprint

The distinct pattern of dark bands formed by separated DNA fragments of varying repeat lengths, reflecting individual genetic uniqueness in non-coding regions.

Uses of DNA profiling

1. Forensics

2. Diagnosing inherited diseases

3. Paternity tests

Disadvantages of DNA profiling

1. violation of privacy (parents sign legal doc confirming paternity)

2. Manipulation of data

3. Accuracy = competency of equipment

Tetracycline

An antibiotic that counteracts bacterial infections by inhibiting the attachment of amino-acid-bearing tRNA to bacterial ribosomes during translation.

Chloramphenicol

An antibiotic that inhibits bacterial protein synthesis by preventing the formation of peptide bonds between amino acids.