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Genetics
Study of genes, heredity, and how genetic information is maintained, expressed, and transmitted.
Gene
A segment of DNA (or RNA in viruses) that encodes a functional product (protein or functional RNA).
Gene Expression
The process by which information from a gene is used to synthesize a functional product, following DNA → RNA → Protein.
Chromosome
A structure composed of DNA and proteins that carries genetic information in the form of genes.
Genome
The complete set of genetic material in an organism.
Genotype
The genetic makeup of an organism; all the genes it carries.
Phenotype
The observable characteristics or traits of an organism, resulting from the interaction of its genotype and environment.
Recombination
The process by which genetic material is rearranged (e.g., crossing over or horizontal gene transfer) to increase diversity.
Plasmid
A small, circular, double-stranded DNA molecule that replicates independently of chromosomal DNA, commonly found in bacteria.
DNA Structure
DNA is a double-stranded helix with a sugar-phosphate backbone and nitrogenous bases (A, T, G, C) that pair (A-T, G-C).
Double-Stranded DNA
DNA composed of two complementary strands forming a helix.
Single-Stranded DNA
DNA that consists of one strand, typically found in viruses or during replication before reannealing.
DNA Base Pairing Rules
In DNA, Adenine pairs with Thymine and Guanine pairs with Cytosine.
Semiconservative Replication
A replication process where each new DNA molecule contains one old (parental) strand and one newly synthesized strand.
Helicase
An enzyme that unwinds and separates the double-stranded DNA into single strands during replication.
Single-Stranded Binding Proteins (SSBs)
Proteins that bind to single-stranded DNA to prevent reannealing during replication.
Primase
An RNA polymerase that synthesizes RNA primers required for DNA polymerase to begin synthesis.
DNA Polymerase
The enzyme responsible for synthesizing new DNA strands by adding nucleotides complementary to the template.
DNA Ligase
An enzyme that joins Okazaki fragments together on the lagging strand during replication.
Central Dogma
The flow of genetic information: DNA → RNA → Protein.
Transcription
The process of synthesizing RNA from a DNA template.
Translation
The process by which ribosomes decode mRNA to synthesize proteins.
RNA Polymerase
The enzyme that synthesizes RNA from a DNA template during transcription.
Promoter Region
A specific DNA sequence upstream of a gene where RNA polymerase binds to start transcription.
DNA to RNA Base Pairing
During transcription, DNA Adenine pairs with RNA Uracil, Thymine with Adenine, Cytosine with Guanine, and Guanine with Cytosine.
mRNA (Messenger RNA)
An RNA copy of a gene that carries genetic information from the DNA in the nucleus to the ribosome.
tRNA (Transfer RNA)
RNA that carries amino acids to the ribosome during protein synthesis.
rRNA (Ribosomal RNA)
RNA that, along with proteins, forms the ribosomes which facilitate protein synthesis.
Prokaryotic Transcription & Translation
In prokaryotes, both processes occur in the cytoplasm and are often coupled, with few or no introns.
Eukaryotic Transcription
In eukaryotes, transcription occurs in the nucleus and is followed by post-transcriptional modifications.
Post-transcriptional Modifications
Processes such as 5' capping, polyadenylation, and splicing that modify pre-mRNA in eukaryotes.
Introns
Non-coding regions within a gene that are removed during mRNA splicing.
Exons
Coding regions of a gene that remain in the mature mRNA after splicing.
snRNPs (Small Nuclear Ribonucleoproteins)
Components of the spliceosome that help remove introns from pre-mRNA.
Ribozymes
RNA molecules with catalytic activity that can catalyze their own splicing.
Coupled Transcription and Translation
In prokaryotes, translation begins on an mRNA even while it is still being transcribed.
Proofreading Activity
The ability of DNA polymerase to check and correct errors during DNA replication by removing misincorporated nucleotides.
Viral Polymerases and Proofreading
Many viral DNA/RNA polymerases lack proofreading activity, leading to a higher mutation rate and more variants.
Mutation
A change in the nucleotide sequence of DNA that may alter protein function.
Mutation
Mutations can produce nonfunctional proteins or, rarely, advantageous traits like antibiotic resistance (often at a fitness cost).
Translation Process
The process by which ribosomes synthesize proteins from the mRNA template, using tRNA to add amino acids.
Ribosome Function
Ribosomes decode the mRNA sequence and facilitate the assembly of amino acids into a polypeptide.
Operon
A cluster of genes under the control of a single promoter and operator, transcribed as one mRNA.
Promoter (Operon)
The DNA sequence where RNA polymerase binds to initiate transcription of an operon.
Operator
A DNA sequence within an operon where repressor proteins bind to regulate transcription.
Repressor Protein
A protein that binds to the operator to block transcription of the operon's genes.
Constitutive Genes
Genes that are continuously expressed (always "on"), such as those for basic cellular functions.
Inducible Operon
An operon that is normally off but can be turned on in the presence of an inducer (e.g., lac operon).
Repressible Operon
An operon that is normally on but can be turned off by a repressor when a corepressor is present.
Lac Operon
An inducible operon in E. coli that controls the metabolism of lactose.
I Gene (in Lac Operon)
Encodes the repressor protein that binds to the operator to inhibit transcription when lactose is absent.
lacZ Gene
Encodes β-galactosidase, the enzyme that breaks down lactose into glucose and galactose.
lacY Gene
Encodes lac permease, a protein that facilitates lactose uptake into the cell.
lacA Gene
Encodes transacetylase, a less critical enzyme in lactose metabolism.
Lac Operon Regulation (On)
The lac operon is active when lactose is present (and glucose is low) because allolactose binds the repressor, preventing its binding to the operator.
Lac Operon Regulation (Off)
In the absence of lactose, the repressor binds to the operator, blocking transcription of lac operon genes.
Advantageous Mutations
Mutations that may confer benefits such as antibiotic resistance, though they often come with a growth or fitness cost.
Transformation
The uptake of free DNA or plasmids from the environment by bacteria; demonstrated in Griffith's experiment.
Competence (Transformation)
The state in which a bacterium is capable of taking up external DNA.
Conjugation
A process of direct DNA transfer between bacteria via cell-to-cell contact using a sex pilus.
Sex Pilus
A tube-like structure that connects two bacterial cells during conjugation to transfer DNA.
F Plasmid
A plasmid that carries genes for conjugation; cells with it are called F+.
F+ Cell
A bacterial cell that possesses the F plasmid and can donate DNA during conjugation.
F- Cell
A bacterial cell lacking the F plasmid, which can receive DNA during conjugation.
Hfr Cell
A cell in which the F plasmid is integrated into the bacterial chromosome, enabling high-frequency chromosomal gene transfer.
High-Frequency Recombination (Hfr)
Refers to the increased rate at which chromosomal genes are transferred during conjugation from Hfr cells.
Transduction
The process of transferring bacterial DNA from one cell to another via bacteriophages.
Bacteriophage
A virus that infects bacteria and can mediate DNA transfer (transduction).
Biotechnology
The use of living organisms or cells to produce products and solve problems (e.g., production of vaccines, enzymes).
Recombinant DNA (rDNA) Technology
The process of combining DNA from different sources to create new genetic combinations for research or product development.
Genetic Engineering
The manipulation of an organism's genes using biotechnology; for example, producing human insulin in E. coli.
Human Insulin Production (rDNA)
An example of genetic engineering where the human insulin gene is inserted into E. coli for insulin production.
Restriction Enzymes
Enzymes that cut DNA at specific sequences; used in biotechnology for cloning and naturally in bacteria for defense against viral DNA.
Bacterial DNA Methylation
A process by which bacteria protect their own DNA from restriction enzymes by adding methyl groups.
Vector
A DNA molecule (often a plasmid) used to carry foreign DNA into a host cell.
Shuttle Vector
A vector that can replicate in two different host organisms (e.g., both bacteria and eukaryotes).
cDNA
Complementary DNA synthesized from mature mRNA using reverse transcriptase; contains only exons.
Reverse Transcriptase
An RNA-dependent DNA polymerase (from retroviruses such as HIV) used to make DNA copies from RNA templates.
cDNA Library
A collection of cDNA clones representing all the mRNA expressed by an organism.
Genomic Library
A collection of DNA fragments that represents the entire genome, including non-coding regions.
Synthetic DNA
Custom-made DNA sequences produced chemically in the laboratory.
PCR (Polymerase Chain Reaction)
A technique to amplify specific DNA sequences exponentially from a small initial sample.
PCR Uses
Used for cloning, pathogen detection, gene expression analysis, sequencing, and diagnostics.
PCR Template DNA
The DNA containing the region of interest that will be amplified in PCR.
PCR Primers
Short DNA sequences that anneal to the flanking regions of the target DNA to initiate PCR.
dNTPs in PCR
The nucleotide building blocks required for DNA synthesis during PCR.
Taq Polymerase
A heat-stable DNA polymerase from thermophilic bacteria, critical for PCR due to its resistance to high temperatures.
PCR Buffer and Mg²⁺
Components that maintain optimal pH and ion concentration for PCR enzyme activity.
PCR Denaturation Step
The step in PCR where high heat separates the double-stranded DNA into single strands.
PCR Annealing Step
The step in PCR where the temperature is lowered to allow primers to bind to the target DNA.
PCR Extension Step
The step in PCR where Taq polymerase extends the primers, synthesizing new DNA strands.
Primer Design
The process of selecting primer sequences that specifically amplify the desired DNA region.
cDNA as a Gene Source
cDNA is derived from mRNA and represents only the coding regions (exons) of a gene.
cDNA Library vs. Genomic Library
A cDNA library contains only expressed genes, whereas a genomic library contains the entire genome.
Reverse Transcriptase Source
Reverse transcriptase is isolated from retroviruses (family Retroviridae).
Gene Silencing
The process of reducing or eliminating gene expression.
siRNA (Small Interfering RNA)
Short RNA molecules that bind to specific mRNA sequences to trigger their degradation and silence gene expression.
DNA Fingerprinting
A technique using restriction enzyme digestion and gel electrophoresis to generate a DNA fragment pattern for identification.
CRISPR
A gene editing tool derived from bacterial immune systems that can target and modify specific DNA sequences.
CRISPR Applications
Potential uses include gene therapy for genetic disorders, such as sickle cell disease.
