Charles Darwin's first sketch of an evolutionary tree from his First Notebook on Transmutation of Species (1837)

Charles Darwin's first sketch of an evolutionary tree from his First Notebook on Transmutation of Species (1837).

Evolution is change in the gene frequency of a population over successive generations. Over large spans of time, over many generations, the processes of evolution lead to the descent of different species from a common ancestor. The evolutionary framework provides the central, coherent scientific basis to understand the diversity of life on Earth.

Although the new MCAT has reduced the importance of population biology and ecology for the exam, there is still the requirement to have a basic vocabulary to describe evolutionary processes including understanding fitness, selection, speciation, and the differences between microevolution and macroevolution.

WikiPremed Resources

The Molecular Biology Laboratory Images
Image gallery for study with links to larger teaching JPEGs for classroom presentation

Question Drill for Evolution
Conceptual Vocabulary Self-Test

Basic Terms Crossword Puzzle

Basic Puzzle Solution

Learning Goals


Be able to describe the methods involved in common electrophoresis procedures including SDS-PAGE of proteins, denaturing PAGE of DNA & RNA, and electrophoresis of DNA & RNA using agarose gels.

Be familiar with a broad array of chromatographic techniques including column chromatography, gas-liquid chromatography, HPLC, paper chromatography, TLC, size-exclusion, ion-exchange, and affinity chromatography.

Know the basic principles involved in the techniques for sequencing of DNA (especially Sanger) and protein sequencing (especially Edman).

Be able to relate the laboratory protocols of the most commonly employed wet-lab assay techniques in the molecular biology laboratory including Southern blot, northern blot, ELISA, and western blot.

Understand the PCR technique enough to be able to explain the basic method.

Understand the role in gene expression analysis of such techniques as northern blotting, RT-qPCR, and in-situ hybridization for RNA and western blotting and ELISA for protein.

Familiarize yourself with the range of molecular biology techniques which the MCAT won't necessarily assume extensive prior knowledge but may present in passages such as S1 mapping, Dnase footprinting, or mobility shift assay.

Be able to relate temporal-spatial patterns of gene expression to the differentiation potential of stem cells.

Master a working familiarity with recombinant DNA technology including the purpose of restriction endonucleases, the variety of vectors available, and cloning techniques.

Be aware of how cDNA is prepared and the techniques involved in the generation of cDNA libraries.

Have up-to-date knowledge of the latest advances on the frontiers of applied biotechnology in medicine, agriculture, forensics and be able to intelligently discuss issues of safety and ethics in biotechnology research and application.

Suggested Assignments

Review the terminology for the molecular biology laboratory using the question server. Complete the fundamental terms crossword puzzle. Here is the solution to the puzzle.

Read pp. 1-13 in ExamKrackers Biology II. Perform practice items 1-8 on pg. 14. (This section has treatments of evolution as well as viruses and bacteria).

Conceptual Vocabulary for Evolution

Chromatography is the collective term for laboratory techniques which separate analytes dissolved in a mobile phase by passing them through a stationary phase.
Gel electrophoresis
Gel electrophoresis is a technique used for the separation of biological molecules using an electric field.
DNA electrophoresis
DNA electrophoresis is an analytical technique used to separate DNA fragments by size though the use of an electric field which forces the fragments to migrate through a gel.
Agarose is a material used to form a common type of electrophoresis gel which is derived from the cell membranes of some species of red algae or seaweed.
Capillary electrophoresis
Capillary electrophoresis separates biological macromolecules based on their size to charge ratio in the interior of a very narrow tube filled with an electrolyte.
Centrifugation is a process that involves the use of the centripetal force for the separation of mixtures.
DNA sequencing
The term DNA sequencing encompasses biochemical methods for determining the order of the nucleotide bases in a DNA oligonucleotide.
Polymerase chain reaction
The polymerase chain reaction is a technique widely used in molecular biology to exponentially amplify a fragment of DNA by in vitro enzymatic replication.
Restriction enzyme
A restriction enzyme is an enzyme that cuts double-stranded DNA in such a way that the fragments from different chromosomes or genes can be spliced together by ligases.
SDS-PAGE, officially sodium dodecyl sulfate polyacrylamide gel electrophoresis, is a technique used to separate proteins according to their electrophoretic mobility.
Thin layer chromatography
Thin layer chromatography is a chromatography technique involving a stationary phase consisting of a thin patina of adsorbent material immobilised on a flat, inert carrier sheet.
Dialysis is the process of separating molecules in solution by the difference in their rates of diffusion through a semipermeable membrane.
Supernate refers to the liquid or clear fluid above a sediment or precipitate.
Cloning vector
A cloning vector is a small DNA vehicle that carries a foreign DNA fragment.
A plasmid is a DNA molecule separate from chromosomal DNA which is capable of autonomous replication. It is typically circular and double-stranded.
A prophage is a phage genome inserted as part of the linear structure of the DNA chromosome of a bacterium.
Immunostaining is a general term in biochemistry that applies to any use of an antibody-based method to detect a specific protein in a sample.
Fractionation is a separation process in which a certain quantity of a mixture is divided up in a large number of smaller quantities in which the composition changes according to a gradient.
Dideoxynucleotides are nucleotides lacking a three prime hydroxyl group on their deoxyribose sugar. After one is added by a DNA polymerase to a growing nucleotide chain, no further nucleotides can be added.
Shotgun sequencing
In shotgun sequencing, DNA is broken up randomly into numerous small segments, which are sequenced. The process is repeated until multiple overlapping reads for the target DNA are obtained
Edman degradation
Edman degradation is a method of sequencing amino acids in a peptide in which the amino-terminal residue is labeled and cleaved from the peptide without disrupting the peptide bonds between other amino acid residues.
Taq polymerase
Taq polymerase is a thermostable DNA polymerase named after the thermophilic bacterium Thermus aquaticus from which it was isolated. This enzyme is able to withstand the high temperature required during PCR.
Transgenic bacteria
Transgenic bacteria refers to bacteria which have been genetically engineered.
Molecular cloning
Molecular cloning refers to the procedure of isolating a defined DNA sequence and obtaining multiple copies of it in vivo.
Fertility factor
The Fertility factor (also known as F factor or sex factor) is a bacterial DNA sequence that allows a bacterium to produce a sex pilus necessary for conjugation.
A pilus is a hairlike appendage found on the surface of many bacteria.
Transformation is the genetic alteration of a cell resulting from the uptake and expression of foreign genetic material.
Hybridization probe
A hybridization probe is a labeled fragment of DNA of variable length which is used to detect in DNA or RNA samples the presence of nucleotide sequences that are complementary to the sequence in the probe.
In ELISA technique an unknown amount of antigen is affixed to a surface, and then a specific labeled antibody is washed over the surface so that it can bind the antigen.
Ion-exchange Chromatography
Ion-exchange chromatography is a process that allows the separation of ions and polar molecules based on the charge properties of the molecules.
Affinity chromatography
Affinity chromatography is a chromatographic method of separating biochemical mixtures, based on a highly specific biologic interaction such as that between antigen and antibody or enzyme and substrate.
The ultracentrifuge is a centrifuge optimized for spinning a rotor at very high speeds, capable of generating acceleration as high as 1,000,000 g.
Peptide mass fingerprinting
In peptide mass fingerprinting an unknown protein is cleaved into peptides by a protease such as Trypsin to form a collection of peptides serving as a unique identifier of the unknown protein.
Restriction digest
A restriction digest is a procedure which uses a restriction enzyme to selectively cleave DNA strands into shorter segments, which are more suitable for analytical techniques such as chromatography.
Agrobacterium is a genus of Gram-negative bacteria that causes tumors in plants, well known for its ability to transfer DNA between itself and plants.
cDNA library
A cDNA library is a collection of clones containing cDNAs. These are often intended to represent as many as possible of the mRNAs contained within a cell.
In molecular biology, a library is a collection of molecules in a stable form that represents some aspect of an organism.
Northern blot
The Northern blot is a technique used in molecular biology research to study gene expression which analyzes RNA by electrophoresis, transfer to a membrane, and detection with a hybridization probe.
Southern blot
The Southern blot is a technique used in molecular biology research to study gene expression which analyzes DNA by electrophoresis, transfer to a membrane, and detection with a hybridization probe.
An autoradiograph is an image produced on an x-ray film or nuclear emulsion by the pattern of decay emissions from a distribution of a radioactive substance.
Western blot
The Western blot is a technique used in molecular biology research which analyzes proteins by electrophoresis, transfer to a membrane, and detection with an antibody probe.
The eluent in chromatography is the liquid or gas entering a chromatographic bed.
High performance liquid chromatography
In high-performance liquid chromatography (HPLC) a liquid mobile phase containing the analyte is pumped at high pressure through a column of the stationary phase.
Reversed-phase chromatography
Reverse-phase chromatography includes any chromatographic method that uses a non-polar stationary phase.
Reverse transcription polymerase chain reaction
Reverse transcription polymerase chain reaction is a laboratory technique for amplifying a defined piece of a ribonucleic acid (RNA) molecule.
Amplicons are pieces of DNA formed as the products of natural or artificial amplification events.
An adapter in genetics engineering is a short, chemically synthesized, double stranded DNA molecule which is used to link the ends of two other DNA molecules.
A lysogen is a phage that does not go into a lytic cycle but instead either integrates into the host bacteria's chromosome or lives as a stable plasmid within the host cell.
Competence is the ability of a cell to take up extracellular DNA from its environment.
In situ hybridization
In situ hybridization is a technique that uses a labeled DNA or RNA probe to localize a specific DNA or RNA sequence in a portion or section of tissue.
DNA microarray
A DNA microarray (also commonly known as gene or genome chip, DNA chip, or gene array) is a collection of microscopic DNA spots arrayed on a solid surface by covalent attachment to a chemical matrix.
Advanced terms that may appear in context in MCAT passages
Protein microarray
A protein microarray is a piece of glass on which different molecules of protein have been affixed at separate locations in an ordered manner thus forming a microscopic array.
Ethidium bromide
Ethidium bromide is an intercalating agent commonly used as a nucleic acid stain in molecular biology laboratories for techniques such as agarose gel electrophoresis.
Secondary antibody
A secondary antibody is an antibody that binds to a primary antibody usually as part of a detection, purification or cell sorting application.
Silica gel
Silica gel is a granular, porous form of silica which is often used in chromatography as a stationary phase.
Size exclusion chromatography
Size exclusion chromatography is a chromatographic method in which particles are separated based on their size, or in more technical terms, their hydrodynamic volume.
Differential centrifugation
Differential centrifugation is a procedure in which a homogenate is subjected to repeated centrifugations in which, after each time, the pellet is removed and the centrifugal force is increased.
Nested polymerase chain reaction
Nested polymerase chain reaction is a modification of polymerase chain reaction intended to reduce the contaminations in products due to the amplification of unexpected primer binding sites.
Restriction modification system
The restriction modification system based on sequence specific restriction enzymes is used by bacteria to protect themselves from foreign DNA, such as bacteriophages.
Endolysin is a generic term describing an enzyme that lyses a bacterial membrane.
Hok/sok system
The host killing/suppressor of killing system, also known as hok/sok system is a postsegregational killing system of the plasmid R1 of Escherichia coli.
Gene knockout
A gene knockout is a genetically engineered organism that carries one or more genes in its chromosomes that have been made inoperative.
Phage display
Phage display is a test to screen for protein interactions by integrating multiple genes from a gene bank into phage.
Southwestern blot
Southwestern blotting, based along the lines of Southern blotting, involves characterizing proteins that bind to DNA.
Van Deemter's equation
Van Deemter's equation in chromatography relates the variance per unit length of a separation column to the linear mobile phase velocity by considering physical, kinetic, and thermodynamic properties of a separation.
Aqueous normal phase chromatography
Aqueous normal phase chromatography is a chromatographic technique which encompasses the mobile phase region between reversed-phase chromatography and organic normal phase chromatography.
Multiplex Ligation-dependent Probe Amplification
Multiplex ligation-dependent probe amplification is a variation of the polymerase chain reaction that permits multiple targets to be amplified with only a single primer pair.
Hfr cell
An hfr cell is a bacterium with a conjugative plasmid integrated into its genomic DNA.
Bacterial artificial chromosome
A bacterial artificial chromosome is a DNA construct, based on a fertility plasmid, used for transforming and cloning in bacteria.
Yeast artificial chromosome
A yeast artificial chromosome (YAC) is a vector used to clone large DNA fragments which contains the telomeric, centromeric, and replication origin sequences needed for replication.
Multiple cloning site
A multiple cloning site, also called a polylinker, is a short segment of DNA which contains many, usually 20 or more, restriction sites - a standard feature of engineered plasmids.
Beta-lactamases are enzymes produced by some bacteria and are responsible for their resistance to beta-lactam antibiotics like penicillins, cephalosporins, cephamycins and carbapenems.
Blue white screen
The blue-white screen is a molecular technique that allows for the detection of successful ligations in vector-based gene cloning.
X-gal is a galactoside and indole used in gene cloning to indicate whether a bacterium expresses the beta-galactosidase enzyme, which is encoded by the lacZ gene.
Electrophoretic mobility shift assay
An electrophoretic mobility shift assay is a common technique used to study protein-DNA or protein-RNA interactions.
DNase footprinting assay
A DNase footprinting assay is a technique from molecular biology that detects DNA-protein interaction using the fact that a protein bound to DNA will often protect that DNA from enzymatic cleavage.
SNP array
An SNP array is a type of DNA microarray which is used to detect polymorphisms within a population.
ChIP-on-chip is a technique that combines chromatin immunoprecipitation (ChIP) with microarray technology (chip).
A phagemid or phasmid is a type of cloning vector developed as a co-infection of the M13 helper phage and plasmids to produce a smaller version of the virus.

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