Cellular Reproduction

Each list begins with basic conceptual vocabulary you need to know for MCAT questions and proceeds to advanced terms that might appear in context in MCAT passages. The terms are links to Wikipedia articles.
Cell division
Cell division is a process by which a cell, called the parent cell, divides into two cells, called daughter cells.
Binary fission
Binary fission is the form of asexual reproduction in most prokaryotes by which one cell divides into two cells of the same size.
DNA replication
DNA replication is the process of copying a double-stranded DNA molecule.
Cell cycle
The cell cycle is the series of events that take place in a eukaryotic cell leading to its replication.
A chromosome is a single large macromolecule of DNA, and constitutes a physically organized form of DNA in a cell.
Mitosis is the process by which a cell duplicates its genetic information in order to generate two, identical, daughter cells.
Prophase is a stage of mitosis in which chromatin condenses into a highly ordered structure called a chromosome.
Metaphase is the stage of mitosis in the eukaryotic cell cycle in which condensed chromosomes, carrying genetic information, align in the middle of the cell before being separated into each of the two daughter cells.
Genetic recombination
Genetic recombination is the process by which a strand of DNA is broken and then joined to the end of a different DNA molecule.
Crossing over
Crossing over is the process by which two chromosomes, paired up during prophase 1 of meiosis, exchange some portion of their DNA.
Homologous recombination
Homologous recombination involves the alignment of similar sequences, a crossover between the aligned DNA strands, and breaking and repair of the DNA to produce an exchange of material between the strands.
Anaphase is the stage of mitosis when chromosomes separate in a eukaryotic cell.
Meiosis is the process by which one diploid eukaryotic cell divides to generate four haploid cells often called gametes.
Semiconservative replication
Semiconservative replication describes the method by which DNA is replicated which produces two copies each containing one of the original strands and one entirely new strand.
Lagging strand
The lagging strand is the DNA strand opposite the replication fork from the leading strand.
Replication fork
The replication fork is a structure that forms during DNA replication having two branching prongs, each one made up of a single strand of DNA.
Leading strand
The leading strand is the DNA strand at the opposite side of the replication fork from the lagging strand.
DNA polymerase
A DNA polymerase is an enzyme that assists in DNA replication, catalyzing the polymerization of deoxyribonucleotides alongside a DNA strand.
DNA polymerase III holoenzyme
DNA polymerase III holoenzyme is the primary enzyme complex involved in prokaryotic DNA replication.
Mutations are changes to the base pair sequence of the genetic material of an organism.
A mutagen is a physical or chemical agent that changes the genetic information of an organism.
Genetic insertion
Genetic insertion is the addition of one or more nucleotide base pairs into a genetic sequence.
Interphase is a phase of the cell cycle, defined only by the absence of cell division.
A chromatid is one of two identical strands of DNA making up a chromosome that are joined at their centromeres, for the process of nuclear division.
A centromere is the region in the middle of a chromosome where sister chromatids join in the double chromosomal structure during mitosis, prophase and metaphase.
Sister chromatids
Sister chromatids are identical copies of a chromosome.
Homologous chromosome
Homologous chromosomes are non-identical chromosomes that contain information for the same biological features and contain the same genes at the same loci but possibly different genetic information at those genes.
The kinetochore is the protein structure in eukaryotes which assembles on the centromere and links the chromosome to microtubule polymers from the mitotic spindle during mitosis and meiosis.
Prometaphase is the phase of mitosis following prophase and preceding metaphase, in eukaryotic somatic cells.
Spindle apparatus
During cell division, the spindle apparatus pulls apart the chromosomes into the two daughter cells.
Telophase is a stage in either meiosis or mitosis in which nuclei reform and chromatin loses its condensed state.
A deletion is a mutation in which a part of a chromosome or a sequence of DNA is missing.
Chromosomal inversion
An inversion is a chromosome rearrangement in which a segment of a chromosome is reversed end to end.
Frameshift mutation
A frameshift mutation is a genetic mutation caused by inserts or deletes from a DNA sequence of a number of nucleotides not evenly divisible by three.
Transposons are sequences of DNA that can move around to different positions within the genome of a single cell, a process called transposition.
Cytokinesis is the process whereby the cytoplasm of a single cell is divided to spawn two daughter cells.
Okazaki fragment
An Okazaki fragment is a relatively short fragment of DNA, with an RNA primer at the five prime terminus, created on the lagging strand during DNA replication.
A primer is a nucleic acid strand, or a related molecule, that serves as a starting strand of nucleotides for DNA polymerase to add to.
DNA polymerase I
DNA polymerase I is an enzyme that mediates the process of DNA replication in prokaryotes, an example of a processive enzyme - an enzyme which catalyzes a series of polymerisations.
Histones are the chief protein components of chromatin. They act as spools around which DNA winds, and they play a role in gene regulation.
A telomere is a region of highly repetitive DNA at the end of a linear chromosome that functions as a disposable buffer.
G1 phase
The G1 phase is a period in the cell cycle during interphase, after cytokinesis and before the S phase.
Synthesis phase
The S phase, short for synthesis phase, is a period in the cell cycle during interphase, between G1 phase and the G2 phase.
G2 phase
The G2 phase is the third, final, and usually the shortest subphase during interphase within the cell cycle in which the cell undergoes a period of rapid growth to prepare for mitosis.
Germline mutation
A germline mutation is any detectable, heritable variation in the lineage of germ cells.
DNA repair
DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome.
Point mutation
A point mutation, or single base substitution, is a type of mutation that causes the replacement of a single base nucleotide with another nucleotide.
Nonsense mutation
A nonsense mutation is a point mutation in a sequence of DNA that results in a premature stop codon, or a nonsense codon in the transcribed mRNA, and possibly a truncated, and often nonfunctional protein product.
Synaptonemal complex
The synaptonemal complex is a protein structure that forms between two homologous chromosomes during meiosis which is thought to mediate chromosome pairing, synapsis, and recombination.
Synapsis, also called syndesis, is the pairing of two homologous chromosomes that occurs during meiosis.
Crossing over
Crossing over is the process by which two chromosomes, paired up during prophase 1 of meiosis, exchange some portion of their DNA.
Origin of replication
The origin of replication is a particular DNA sequence at which DNA replication is initiated.
DNA primase is activated by DNA helicase to synthesize a short RNA primer as a starting point for replication.
DNA ligase
DNA ligase is a particular type of ligase that can link together strands that have double-strand breaks
The replisome is made up of two DNA polymerase III core enzymes, which are each made up of three subunits: one with polymerization activity, one with proofreading ability and one that stimulates the proofreading.
Ori is the DNA sequence that signals for the origin of replication, sometimes referred to simply as origin.
Heterochromatin is a tightly packed form of DNA. Its major characteristic is that transcription is limited.
Missense mutation
Missense mutations or nonsynonymous mutations are types of point mutations where a single nucleotide is changed to cause substitution of a different amino acid.
Silent mutation
Silent mutations are DNA mutations that do not result in a change to the amino acid sequence of a protein.
Bacterial conjugation
Bacterial conjugation is the transfer of genetic material between bacteria through direct cell-to-cell contact.
Transduction is the process by which bacterial DNA is moved from one bacterium to another by a virus.
Gene conversion
Gene conversion may occur during meiotic division through a process by which DNA sequence information is transferred from one DNA helix to another DNA helix, whose sequence is altered.
Insertion sequence
An insertion sequence is a short DNA sequence that acts as a simple transposable element.
Euchromatin is a lightly packed form of chromatin that is rich in gene concentration and is often under active transcription.
Cell cycle checkpoint
Cell cycle checkpoints are control mechanisms that ensure the fidelity of cell division in eukaryotic cells.
Ploidy is the number of homologous sets of chromosomes in a biological cell.
Gametogenesis is a process by which the diploid germ cells undergo a number of chromosomal and morphological changes to form mature haploid gametes.
A gametocyte is a eukaryotic germ cell that divides by mitosis into similar cells or by meiosis into gametes during gametogenesis.
Sometimes referred to as a tetrad, bivalents are a pair of associated homologous chromosomes formed after replication during meiosis.
A dyad is a pair of sister chromatids.
Helicases are motor proteins that move directionally along a nucleic acid phosphodiester backbone, separating two annealed nucleic acid strands.
DNA clamp
A DNA clamp is a protein fold that serves as a processivity-promoting factor in DNA replication.
Retrotransposons are genetic elements that can amplify themselves in a genome and are ubiquitous components of the DNA of many eukaryotic organisms.
Chromosomal translocation
A chromosome translocation is a chromosome abnormality caused by rearrangement of parts between nonhomologous chromosomes.
Transfection describes the introduction of foreign material into eukaryotic cells, which may occur with genetic material such as supercoiled plasmid DNA.
Horizontal gene transfer
Horizontal or lateral gene transfer is any process in which an organism transfers genetic material to another cell that is not its offspring.
Mobile genetic elements
Mobile genetic elements are a type of DNA that can move around within the genome including transposons, plasmids, bacteriophage elements and group II introns.
Griffith's experiment
Griffith's experiment, conducted in 1928, was one of the first experiments suggesting that bacteria are capable of transferring genetic information though a process known as transformation.
Single-strand binding protein
Single-strand binding protein binds single stranded regions of DNA to prevent premature reannealing.
DNA gyrase
DNA gyrase is a type II topoisomerase that introduces negative supercoils into DNA or relaxes positive supercoils.
Topoisomerases are isomerase enzymes that acts on the topology of DNA.
Pre-replication complex
A pre-replication complex is a protein complex that forms at the origin of replication during the initiation step of DNA replication.
Origin Recognition Complex
Origin recognition complex is a multisubunit complex existing in the replication procedure of DNA, marking the replication origin by binding to and marking ori sequences in all eukaryotes.
Cleavage furrow
The cleavage furrow is the indentation that begins the process of cleavage, by which animal and some algal cells undergo cytokinesis.
Germ cell
A germ cell is part of the sequence cells that have genetic material that may be passed to an offspring.
dnaB helicase
DnaB helicase is an enzyme in prokaryotes which opens the replication fork during DNA replication.
Gene duplication
Gene duplication is any creation of a repeat of a region of DNA that contains a gene.
Polyploidy is the condition of some biological cells and organisms manifested by the presence of more than two homologous sets of chromosomes.
Transposase is an enzyme that binds to single-stranded DNA and can incorporate it into genomic DNA.
Mutation rate
The mutation rate is the chance of a mutation occurring in an organism or gene in each generation.
Inverted repeat
An inverted repeat is a sequence of nucleotides that is the reversed complement of another sequence further downstream.
Long terminal repeat
Long terminal repeats are found in retroviral DNA flanking functional genes. They encode a specific transposase called integrase which mediates integration of viral DNA into the host chromosome.
A centimorgan (abbreviated cM) is a unit of recombinant frequency for measuring genetic linkage.
Muller's ratchet
Muller's ratchet is the name given to the process by which the genomes of an asexual population accumulate deleterious mutations in an irreversible manner.
Processivity is a measure of the average number of nucleotides added by a DNA polymerase enzyme per association/disassociation with the template.
Rolling circle replication
Rolling circle replication describes a process of nucleic acid replication that can rapidly synthesize multiple copies of circular molecules of DNA or RNA such as plasmids or bacterial nucleoids.
Cell division cycle 6
Cell division cycle 6 is a protein essential for the initiation of DNA replication. Its role is to recruit a complex of six proteins, called the minichromosome maintenance complex to the sites of replication initiation.
Telomerase is an enzyme that adds specific DNA sequence repeats to the three prime end of DNA strands in the telomere regions of eukaryotic chromosomes.
Restriction point
The restriction point is a G1 phase checkpoint in the cell cycle of animal cells. Cells that progress through this point are committed to enter S phase.
Condensins are large protein complexes that play a central role in chromosome assembly and segregation in eukaryotic cells. Even in prokaryotes, ancestral forms regulate the segregation of nucleoids.
Cohesin is the protein responsible for binding the sister chromatids during mitosis after S phase.
Cyclins are a family of proteins involved in the progression of cells through the cell cycle. Their concentration varies in a cyclical fashion during the cell cycle.
Spindle checkpoint
The spindle checkpoint blocks the entry of a cell undergoing mitosis into anaphase until all chromosomes are properly attached to the meiotic or mitotic spindle.
Separase is a cysteine protease responsible for triggering anaphase by hydrolysing cohesin which is the protein responsible for binding sister chromatids during metaphase.
Septins are evolutionary conserved proteins with essential functions in cytokinesis, and more subtle roles throughout the cell cycle. They act as a scaffold, recruiting a plethora of proteins.
The chiasmata are thought to be the points where two homologous chromatids exchange genetic material during chromosomal crossover during meiosis.
Primosome is a complex of seven proteins including DnaG primase, DnaB helicase, and DnaC helicase assistant.
Cell plate
Cell plate formation is the process by which cytokinesis occurs in plants.
Holliday junction
A Holliday junction is a mobile junction between four strands of DNA.
Base excision repair
Base excision repair is a cellular mechanism that can repair damaged DNA during DNA replication involving flipping the mutated base out of the DNA helix and repairing the base alone.
Nucleotide excision repair
Nucleotide excision repair is a DNA repair mechanism involves the removal and replacement of short single-stranded DNA segments.
DNA mismatch repair
Mismatch repair is a system for recognizing and repairing the erroneous insertion, deletion and mis-incorporation of bases that can arise during DNA replication and recombination.
A transition is a mutation changing a purine to another purine nucleotide or a pyrimidine to another pyrimidine nucleotide.
A transversion is a type of point mutation refering to the substitution of a purine for a pyrimidine or vice versa.
Depurination is DNA alteration in which the hydrolysis of a purine base from the deoxyribose-phosphate backbone occurs.
Base analog
A base analog is a chemical that can substitute for a normal nucleobase in nucleic acids.
Intercalation is the reversible inclusion of a molecule (or group) between two other molecules (or groups).
Flap endonuclease
Flap endonucleases are a class of nucleolytic enzymes that act as both exonucleases and structure specific endonucleases on specialised DNA structures.
Septin ring
A septin ring is a collar-shaped structure which forms during cell division along the axis where a plant cell splits.
dnaG is a primase which synthesizes an RNA primer for Okazaki fragments in E. coli.
Klenow fragment
The Klenow fragment is a large protein fragment which is produced when DNA polymerase I from E. coli is cleaved by the protease enzyme subtilisin.
Histone deacetylase
Histone deacetylases are a class of enzymes that remove acetyl groups from an epsilon-N-acetyl lysine amino acid on a histone, causing the histones to wrap more tightly around the DNA.
Maturation promoting factor
Maturation promoting factor (also called mitosis-promoting factor or M-Phase promoting factor) is a protein which stimulates the mitotic and meiotic cell cycles.
Securin is a protein involved in anaphase triggering which helps the transport of separase to the nucleus and inhibits its catalytic activity.
Preprophase is a phase preceding prophase during mitosis in plant cells. This phase does not occur in other eukaryotes such as animals or fungi.
Preprophase band
The preprophase band is a microtubule array found in plant cells that are about to undergo cell division and enter the preprophase stage of the plant cell cycle.
The phragmosome is a sheet of cytoplasm forming in highly vacuolated plant cells in preparation for mitosis.
Aurora A kinase
Aurora A kinase is a member of a family of mitotic serine/threonine kinases implicated with important processes during mitosis in association with the mitotic poles and adjacent spindle microtubules.
Cyclin-dependent kinase
Cyclin-dependent kinases belong to a group of protein kinases originally discovered as being involved in the regulation of the cell cycle. CDK9 is an exception, playing no role in cell cycle regulation.
Anaphase-promoting complex
Anaphase-promoting complex is a complex of several proteins which is activated during mitosis to initiate anaphase.
Fusion gene
A fusion gene is a hybrid gene formed from two previously separate genes which can occur as the result of a translocation, interstitial deletion, or chromosomal inversion.
The mobilome is the total of all mobile genetic elements in a genome.
Replicative transposition
Replicative transposition is a mechanism of transposition in which the transposable element is duplicated during the reaction, so that the transposing entity is a copy of the original element.
AP site
An AP site, meaning apurinic and apyrimidinic, is a location in DNA that does not have either a purine or pyrimidine base, usually due to DNA damage.
Non-homologous end joining
Non-homologous end joining is a pathway that can be used to repair double-strand breaks in DNA.
Loss of heterozygosity
Loss of heterozygosity in a cell represents the loss of one parent's contribution to part of the cell's genome.
AP endonuclease
An AP endonuclease is an enzyme that cuts a strand of DNA on the five prime side of an AP site, as part of DNA base excision repair.
UvrABC endonuclease
UvrABC endonuclease is a multienzyme complex in E.coli bacteria involved in DNA repair mechanism by nucleotide excision repair and it is therefore sometimes called and excinuclease.
Triparental mating
Triparental mating is a form of Bacterial conjugation where a conjugative plasmid present in one bacterial strain assists the transfer of a mobilizable plasmid present in a second bacterial strain into a third bacterial strain.

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