Molecular Biology and Gene Expression Practice Flashcards

Comprehensive vocabulary flashcards covering the molecular basis of genetics, DNA structure, replication, PCR, and gene expression based on the lecture notes.

Molecular Biology

The study of biology at a molecular level, specifically the formation, structure, and function of macromolecules essential to life, such as nucleic acids and proteins.

Transmission Genetics

The branch of genetics that deals with the transmission of traits from parental organisms to their offspring.

Chromosome Theory of Inheritance

The theory stating that chromosomes are discrete physical entities that carry the genes.

Genotype

The combination of alleles found in an organism.

Phenotype

The visible expression of the genotype, with the wild-type being the most common or generally accepted standard.

Nucleotide

A long polymer or chain consisting of three parts: a phosphate group, a deoxyribose sugar (in DNA), and a nitrogen-containing base.

Nucleoside

A molecule consisting of a nitrogenous base linked to a sugar, lacking the phosphoric acid group found in nucleotides.

Semiconservative replication

The mode of DNA replication where each daughter double helix keeps one strand of the parental double helix conserved.

Purines

Double-ring nitrogenous bases, which include Adenine ($A$) and Guanine ($G$).

Pyrimidines

Single-ring nitrogenous bases, which include Cytosine ($C$), Thymine ($T$), and Uracil ($U$).

Phosphodiester bond

The chemical bond that joins the sugars in a DNA or RNA chain through their $5'$ and $3'$ hydroxyl groups.

B-DNA

A right-handed helix that occurs under conditions of high humidity ($95 \%$) and low salt, characterized by $10.5$ bases per turn.

A-DNA

A right-handed helix formed when water content is decreased and salt concentration is increased, featuring $11$ bases per turn and tilted bases.

Z-DNA

A left-handed helix with a zig-zag backbone structure, containing $12$ base pairs per turn, often formed by repeating $GC$ sequences.

Melting temperature ($T_m$)

The temperature at which DNA strands are $\frac{1}{2}$ denatured or dissociated.

Beer-Lambert Law

The law expressed as $I = I_0 10^{-\epsilon dc}$, where absorbance depends on the concentration of the absorbing material and the optical path length.

Electrophoresis

A technique that allows the separation of biomolecules like DNA, RNA, and protein on the basis of size using a matrix like agarose or polyacrylamide.

Ethidium bromide

A fluorescent dye used to stain nucleic acids by intercalating in stacked base pairs and elongating the DNA helix.

Leading strand

The DNA strand synthesized continuously in the $5'$ to $3'$ direction toward the replication fork.

Lagging strand

The DNA strand synthesized discontinuously in short segments called Okazaki fragments.

DNA Helicase

The enzyme responsible for unwinding the DNA double helix during replication.

Polymerase Chain Reaction (PCR)

A technique used to amplify a specific segment of DNA through repeated cycles of denaturation, annealing, and extension.

Taq polymerase

A heat-stable DNA polymerase used in PCR to synthesize new DNA strands.

Transcription

The process by which a DNA sequence is copied into an RNA transcript by the enzyme RNA polymerase.

Promoter

A DNA segment or region upstream of a gene that RNA polymerase recognizes and binds to in order to initiate transcription.

Translation

The process of converting the nucleic acid base pair language of mRNA into the amino acid language of proteins.

Ribosomes

The cell’s protein factories, which in bacteria are $70S$ particles composed of two subunits: $50S$ and $30S$.

Transfer RNA (tRNA)

A small adapter RNA molecule that binds a specific amino acid at one end and contains an anticodon at the other to recognize mRNA codons.

Codon

A triplet sequence of nucleic acid bases in mRNA that stands for one specific amino acid.

Anticodon

A sequence of three nucleotides in a tRNA molecule that is complementary to a codon in mRNA.

Operon

A unit of genetic regulation most common in prokaryotes that includes a promoter, an operator, and one or more structural genes.

Introns

Non-coding sequences in eukaryotic mRNA that are removed during RNA processing.

Exons

Specific sequences in mRNA that are spliced together to form the final coding sequence for protein synthesis.

Silent mutation

A mutation that results in a different codon for the same amino acid, causing no change in the protein product.

Open reading frame (ORF)

The region of mRNA defined by an initiation codon and a termination codon that codes for a polypeptide.