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Module 13 in the Syllabus

Cellular Reproduction Images
Image gallery for study with links to larger teaching JPEGs for classroom presentation

Question Drill for DNA Replication and Cellular Reproduction
Conceptual Vocabulary Self-Test

Basic Terms Crossword Puzzle

Basic Puzzle Solution

Conceptual Vocabulary
Cell divisionCell division is a process by which a cell, called the parent cell, divides into two cells, called daughter cells.
Binary fissionBinary fission is the form of asexual reproduction in most prokaryotes by which one cell divides into two cells of the same size.
DNA replicationDNA replication is the process of copying a double-stranded DNA molecule.
Cell cycleThe cell cycle is the series of events that take place in a eukaryotic cell leading to its replication.
ChromosomeA chromosome is a single large macromolecule of DNA, and constitutes a physically organized form of DNA in a cell.
MitosisMitosis is the process by which a cell duplicates its genetic information in order to generate two, identical, daughter cells.
ProphaseProphase is a stage of mitosis in which chromatin condenses into a highly ordered structure called a chromosome.
MetaphaseMetaphase 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.
AnaphaseAnaphase is the stage of mitosis when chromosomes separate in a eukaryotic cell.
MeiosisMeiosis is the process by which one diploid eukaryotic cell divides to generate four haploid cells often called gametes.
Semiconservative replicationSemiconservative 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 strandThe lagging strand is the DNA strand opposite the replication fork from the leading strand.
Replication forkThe 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 strandThe leading strand is the DNA strand at the opposite side of the replication fork from the lagging strand.
DNA polymeraseA DNA polymerase is an enzyme that assists in DNA replication, catalyzing the polymerization of deoxyribonucleotides alongside a DNA strand.
DNA polymerase III holoenzymeDNA polymerase III holoenzyme is the primary enzyme complex involved in prokaryotic DNA replication.
InterphaseInterphase is a phase of the cell cycle, defined only by the absence of cell division.
ChromatidA 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.
CentromereA 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 chromatidsSister chromatids are identical copies of a chromosome.
Homologous chromosomeHomologous 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.
KinetochoreThe 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.
PrometaphasePrometaphase is the phase of mitosis following prophase and preceding metaphase, in eukaryotic somatic cells.
Spindle apparatusDuring cell division, the spindle apparatus pulls apart the chromosomes into the two daughter cells.
TelophaseTelophase is a stage in either meiosis or mitosis in which nuclei reform and chromatin loses its condensed state.
CytokinesisCytokinesis is the process whereby the cytoplasm of a single cell is divided to spawn two daughter cells.
Okazaki fragmentAn 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.
PrimerA 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 IDNA 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.
HistoneHistones are the chief protein components of chromatin. They act as spools around which DNA winds, and they play a role in gene regulation.
TelomereA telomere is a region of highly repetitive DNA at the end of a linear chromosome that functions as a disposable buffer.
G1 phaseThe G1 phase is a period in the cell cycle during interphase, after cytokinesis and before the S phase.
Synthesis phaseThe S phase, short for synthesis phase, is a period in the cell cycle during interphase, between G1 phase and the G2 phase.
G2 phaseThe 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.
Synaptonemal complexThe synaptonemal complex is a protein structure that forms between two homologous chromosomes during meiosis which is thought to mediate chromosome pairing, synapsis, and recombination.
SynapsisSynapsis, also called syndesis, is the pairing of two homologous chromosomes that occurs during meiosis.
Crossing overCrossing over is the process by which two chromosomes, paired up during prophase 1 of meiosis, exchange some portion of their DNA.
Origin of replicationThe origin of replication is a particular DNA sequence at which DNA replication is initiated.
PrimaseDNA primase is activated by DNA helicase to synthesize a short RNA primer as a starting point for replication.
DNA ligaseDNA ligase is a particular type of ligase that can link together strands that have double-strand breaks
ReplisomeThe 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.
OriOri is the DNA sequence that signals for the origin of replication, sometimes referred to simply as origin.
HeterochromatinHeterochromatin is a tightly packed form of DNA. Its major characteristic is that transcription is limited.
EuchromatinEuchromatin is a lightly packed form of chromatin that is rich in gene concentration and is often under active transcription.
Cell cycle checkpointCell cycle checkpoints are control mechanisms that ensure the fidelity of cell division in eukaryotic cells.
PloidyPloidy is the number of homologous sets of chromosomes in a biological cell.
GametogenesisGametogenesis is a process by which the diploid germ cells undergo a number of chromosomal and morphological changes to form mature haploid gametes.
GametocyteA gametocyte is a eukaryotic germ cell that divides by mitosis into similar cells or by meiosis into gametes during gametogenesis.
BivalentSometimes referred to as a tetrad, bivalents are a pair of associated homologous chromosomes formed after replication during meiosis.
DyadA dyad is a pair of sister chromatids.
HelicaseHelicases are motor proteins that move directionally along a nucleic acid phosphodiester backbone, separating two annealed nucleic acid strands.
DNA clampA DNA clamp is a protein fold that serves as a processivity-promoting factor in DNA replication.
Single-strand binding proteinSingle-strand binding protein binds single stranded regions of DNA to prevent premature reannealing.
DNA gyraseDNA gyrase is a type II topoisomerase that introduces negative supercoils into DNA or relaxes positive supercoils.
TopoisomeraseTopoisomerases are isomerase enzymes that acts on the topology of DNA.
Pre-replication complexA pre-replication complex is a protein complex that forms at the origin of replication during the initiation step of DNA replication.
Origin Recognition ComplexOrigin 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 furrowThe cleavage furrow is the indentation that begins the process of cleavage, by which animal and some algal cells undergo cytokinesis.
Germ cellA germ cell is part of the sequence cells that have genetic material that may be passed to an offspring.
dnaB helicaseDnaB helicase is an enzyme in prokaryotes which opens the replication fork during DNA replication.
Advanced terms that may appear in context in MCAT passages
ProcessivityProcessivity is a measure of the average number of nucleotides added by a DNA polymerase enzyme per association/disassociation with the template.
Rolling circle replicationRolling 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 6Cell 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.
TelomeraseTelomerase 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 pointThe 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.
CondensinCondensins 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.
CohesinCohesin is the protein responsible for binding the sister chromatids during mitosis after S phase.
CyclinCyclins 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 checkpointThe spindle checkpoint blocks the entry of a cell undergoing mitosis into anaphase until all chromosomes are properly attached to the meiotic or mitotic spindle.
SeparaseSeparase is a cysteine protease responsible for triggering anaphase by hydrolysing cohesin which is the protein responsible for binding sister chromatids during metaphase.
SeptinsSeptins 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.
ChiasmataThe chiasmata are thought to be the points where two homologous chromatids exchange genetic material during chromosomal crossover during meiosis.
PrimosomePrimosome is a complex of seven proteins including DnaG primase, DnaB helicase, and DnaC helicase assistant.
Cell plateCell plate formation is the process by which cytokinesis occurs in plants.
Holliday junctionA Holliday junction is a mobile junction between four strands of DNA.
Flap endonucleaseFlap endonucleases are a class of nucleolytic enzymes that act as both exonucleases and structure specific endonucleases on specialised DNA structures.
Septin ringA septin ring is a collar-shaped structure which forms during cell division along the axis where a plant cell splits.
dnaGdnaG is a primase which synthesizes an RNA primer for Okazaki fragments in E. coli.
Klenow fragmentThe 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 deacetylaseHistone 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 factorMaturation promoting factor (also called mitosis-promoting factor or M-Phase promoting factor) is a protein which stimulates the mitotic and meiotic cell cycles.
SecurinSecurin is a protein involved in anaphase triggering which helps the transport of separase to the nucleus and inhibits its catalytic activity.
PreprophasePreprophase is a phase preceding prophase during mitosis in plant cells. This phase does not occur in other eukaryotes such as animals or fungi.
Preprophase bandThe 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.
PhragmosomeThe phragmosome is a sheet of cytoplasm forming in highly vacuolated plant cells in preparation for mitosis.
Aurora A kinaseAurora 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 kinaseCyclin-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 complexAnaphase-promoting complex is a complex of several proteins which is activated during mitosis to initiate anaphase.

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