AP BIO exam terms 1

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codon: A three nucleotide sequence that specifies for a single amino acid. Basic unit of genetic code.
polymerase chain reaction: Lab technique for quickly making multiple copies of a DNA segment in vitro by incubating the fragment with a primer, nucleotides and DNA polymerase.
Independant assortment: Mendel's second law- different alleles will segregate independantly of one another during gamete formation (does not take into account linked genes).
origin of replication: Site where replication of DNA begins, site where DNA polymerase and other proteins initially bind.
trisomy: The nondisjunction of chromosomes during meiosis produces gametes with extra copies of chromosomes. In this type the organism has three chromosomes instead of two. (Down syndrome is trisomy of chromosome 21)
chromatin: In a nondividing cell, a mass of long thin fibers that aren't visible with a light microscope; however before cell division it condenses into chromosomes and becomes visible.
intron: Noncoding regions and sequences of eukaryotic genome
natural selection: Darwin's theory that differential success in the reproduction of organisms with different phenotypes results from interactions with their environments. Evolution occurs- those better suited to the environment will survive to produce more offspring with the those traits.
founder effect: Genetic drift caused by the colonization of limited number from the parent population; the new population will not be genetically representative of the parent population.
punctuated equilibrium: Theory of evolution stating evolutionary change occurs in quick spurts of rapid change followed by longer periods of stasis during which no evolution takes place.
genotype: Genetic makeup of an organism. It determines the phenotype.
gradualism: Theory of evolution stating all evolutionary change has been result of accumulation of small, continuous changes and processes. It was preplaced by punctuated equilibrium.
vestigial organs: Structures that had important functions in ancestors but because of evolution are no longer are of any use.
allele: Alternate versions of a gene; responsible for variation in inherited characters.
chiasma: The intersections of 2 chromosome where crossing over occurs. In crossing over, homologous chromosome exchange segments of genetic material during prophase I of meiosis.
codominance: The phenotype when two alleles affect the phenotype in separate, distinguishable ways; both alleles expressed.
RNA: Nucleic acid polymer, sugar is ribose, nucleotides= adenine, cytosine, guanine, and uracil
histone: A protein molecule that has a slightly positive charge and binds to negatively charged DNA molecule, histone and DNA form chromatin.
retrovirus: Any RNA virus that reproduces by transcribing its RNA into DNA and then inserting the DNA into the chromosome of the host cell, where it undergoes replication with the host.
bottleneck effect: Type of genetic drift that is the result of the drastic reduction of a population usually by natural disaster. The surviving population no longer is genetically representative of the original population.
mutagen: An agent (chemical or physical) that causes an alteration in the DNA sequence.
phage: A virus that infects bacteria, aka bacteriophage.
pinocytosis: A form of endocytosis in which the cell ingests extracellular fluid as well as solutes dissolved in it.
osmotic pressure: A measure of the tendency of water to move from a hypotonic solution to a hypertonic solution across a selectively permeable membrane.
promoter: A specific sequence of nucleotides in DNA that binds to RNA polymerase and indicates the starting point of mRNA transcription.
nucleoulus: A dense, spherical body inside the nucleus of a cell. It is the site of rRNA production.
lysosome: A cellular sac, bound by a membrane in the cytoplasm of eukaryotic cells, that contains hydrolytic enzymes and whose function is to digest macromolecules.
stoma: Plural: stomata Very small pore in the epidermis of plant leaves that is flanked by two guard cells. They are the sites of gas exchange between the environment and the interior of the leaf.
exon: Coding regions of genes in the eukaryotic genome.
homozygous organisms: Have two identical alleles for a given traits, whether they be dominant or recessive.
adaptive radiation: The evolutionary development of numerous new species, all from a common ancestor. In this process, the ancestral species is introduced into a new environment and evolves into a new species. Members of this species are then introduced to a new environment, they evolve; the process occurs until several new species are made.
gamete: A haploid sex cell (egg or sperm); male and female sex cells joing during fertilization to produce a diploid zygote. This type of cell is produced by germ cells.
anaerobic respiration: Cellular process that occurs in the absence of oxygen, 2 molecules of ATP are produced. It can occur by fermentation, which consists of glycolysis plus a series of reactions that regenerate NAD+ to be consumed in glycolysis.
incomplete dominance: F1 hybrids have an appearance that is intermediate between the phenotypes of the two parents. (red flower and white flower = pink flower)
ligand: Any molecule that binds specifically to the receptor of another molecule.
hybrid: A genetic mixture of two parents; the offspring of two genetically different parents. Usually heterozygous for a variety of genes.
synapsis: The lining up and pairing of homologous chromosomes during prophase I of meiosis.
somatic cell: Any plant or animal cell that is not a germ cell in a multicellular animal. They are diploid and produced by mitosis.
photon: A discrete amount of light energy; a quantum of light energy.
repressor: A protein (enzyme) that represses the transcription of a gene by binding to the strand of DNA at the promoter.
yeast: A unicelluar fungus that reproduces by simple cell division or budding and lives in moist habitats.
speciation: Emergence of new species through evolution.
operon: In bacteria and phages, a unit of genetic function that consists of clusters of genes that are coordinately clustered and have related functions. It includes a promoter, an operator, and a transcription unit.
gel electrophoresis: A lab technique used to seperate nucleic acids or proteins on the basis of their size and electric charge by measuring the distance they travel through the gel matrix. Small particles travel more quickly so they go farther.
plastid: Refers to members of a family of closely related plant organelles, including chloroplasts, chromoplasts, and amyloplasts (leucoplasts).
microfilament: Rod-shaped structure made up of actin protein. They make up cytoskeleton and along with myosin in the contraction of muscle cells.
Golgi apparatus: Made of of flattened membranous sacs that modify, store and export products from the endoplasmic reticulum. Has a cis and trans face and packages cell products to be exported.
oxidative phosphorylation: Last stage of cellular respiration during which large amounts of ATP are produced using the energy derived from redox reactions that are occurring in an electron transport chain.
inclusive fitness: An individual's fitness including both genes that the individual passes on to the next generation and the shared genes that the individual helps to pass along through altruism, for example.
peroxisome: A small cell organelle that breaks down macromolecules; this membrane-bound sac contains enzymes that transfer hydrogen ions from substrates to oxygen producing hydrogen peroxide.
Allopatric speciation: Speciation that occurs when populations have geographically separate ranges. It causes and interruption of gene flow between members of the two now distinct populations and results in the evolution of a new species.
stroma: Fluid of the chloroplast, which surrounds the thylakoid membranes.
homologous chromosome: Chromosomes that are paired, have same length, centromere position, staining pattern, possess genes that code for the same characters at the same loci. Each one was inherited from a different parent.
polygenic inheritance: Two or more genes have an effect on one certain phenotypic characteristic.
autosome: Any chromsome that is not a sex chromosome.
pseudopod: A cellular extension that is used in locomotion and feeding in amoeboid cells.
leading strand: Continuously synthesized strand of DNA in replication, synthesized from 5' to 3' by DNA polymerase. Elongates toward replication fork.
restriction site: Specific sequence of DNA where a particular restriction enzyme will recognize and cut; each type of enzyme cuts at a specific site.
telomere: The end of a eukaryotic chromosome; consists of repeated DNA sequences and protects the chromosome from being degraded by continuous replication.
differentiation: Unspecialized cell acquires a specialized form or function.
microtubule: A rod-shaped structure made up of tubulin proteins that exist in the cytoplasm of eukaryotic cells, composes cilia and flagella and contributes to the cytoskeleton.
sex-linked gene: Any gene on a sex chromosome (X or Y).
plasomodesma: A channel in the cell wall of plants through which cytosolic connections pass from adjacent cells.
lagging strand: Discontinuously synthesized strand of DNA that elongates way from the replication fork through the formation of a series of Okazaki fragments. DNA polymerase can only add nucleotides to the 3' end.
viviparous: Animals that give birth to live young, which are born after being nourished in the uterus by blood from the placenta.
species: A group of organisms defined by their ability to interbreed and produce viable offspring.
deuterosome: one of the two coelomate divisions characterized by radial clevage pattern during early development, indeterminate clevage, and the development of blastopore into the anus. Includes echinoderms and chordates.
phenotype: The set of all physical and physiological traits of an organism.
anticodon: A triplet of bases at the end of tRNA. It recognizes the complementary codon on mRNA in the A site of ribosome in translation.
ribosome: Made in the nucleolus, place where protein synthesis occurs, made of rRna and associated proteins.
sympatric speciation: The evolution of a new species that occurs within a population of that species, occurs as a result of mutation or selective breeding.
anion: A negatively charged ion. (Cations are positively charged/ cations and anions attract eachother forming ionic bonds).
plasmid: Circular DNA found in prokaryotes.
dihybrid: An organism that is heterozygous for two different genes. (AaBb)
pleiotropy: Single gene has multiple effects on the phenotype of an organism.
phagocytosis: A form of endocytosis by which the cell takes in macromolecules.
tRNA: An RNA molecule that acts as an interpreter between mRNA and proteins by picking up specific amino acids and pairing them with compatible codons on mRNA during translation.
anaphase: Stage of mitosis during which sister chromatids seperate are pulled along microtubules toward opposite poles of the cell.
restriction enzyme: A bacterial enzyme that recognizes and cuts DNA at specific sites known as restriction sites. They are used to create recombinant DNA (DNA that contains genes from two sources).
sex chromosome: Involved in determining the sex of an individual. (females XX, males XY)
mRNA: Produced during transcription. It is a type of RNA that attaches to ribosomes in the cytoplasm and specifies the primary structure (amino acid sequence) of new proteins. It is synthesized from DNA.
Krebs cycle: Chemical cyle that breaksdown glucose molecule to carbon dioxide. It takes place in the mitochondrion and is the second stage of respiration.
pyruvate: The end product of glycolysis- a three carbon compound. It is convert to acetyl CoA before entering the Krebs cycle.
Barr body: Dense mass inside the nuclear envelope of all female mammalian cells, which is formed by the inactivation during embryonic development of one of the two X chromosomes received from the parents.
glycolysis: The first step in cellular respiration. It produces ATP by converting glucose to pyruvate which is converted to acetyl CoA and enters the Krebs cycle.
interphase: Stage of cell cycle during which the cell prepares for divison, primarily by replicating its DNA. The cell then enters mitosis.
conjugation: One-way transfer of genetic material between two bacterial cells that are joined temporarily.
linked genes: Genes on the same chromosome. The recombination frequency can be used to calculate the position of genes along the chromosome.
DNA polymerase: The enzyme that catalyzes the elongation of the DNA strand at the replication fork by adding nucleotides to the growing chain of DNA.
metaphase: Thrid stage of mitosis, in which microtubules attach to the centromeres of chromosome and move them to the equator (metaphase plate).
nondisjunction: When a pair of chromosomes fails to separate properly during gamete formation; an accident in mitosis or meiosis (failure of sister chromatids to seperate properly).
prophase: First stage of mitosis, meiosis I and meiosis II, during which chromosomes become visible and centrioles move to opposite poles, spindle appears.
prion: A protein that is infectious and thought to be misfolded. They are thought to increase in number by converting similar proteins into misfolded forms and they cause certain infectious diseases such as mad cow disease.
chromosome: A complex that consists of very long DNA molecule and associated proteins (histones). They are threadlike and carry genes of an organism.
allosteric site: Specific site on the enzyme where an allostatic inhibitor or activator binds weakly causing conformational change the either inhibits of stimulates it to catalyze a reaction.
gene flow: Loss or gain of alleles in a population resulting from migration of individuals that are capable of breeding.
amino acid: Monomer of protein (a central carbon attached to an amion group (-NH2) a carboxyl group (-COOH) and a hydrogen atom that is variable and determines the amino acid's chemical properties.
Law of Segregation: Mendel's first law- two variants of a genetic trait (alleles) segregate during gamete formation.
primer: RNA chain bound to a complementary sequence on DNA template; DNA nucleotides are added to the primer at start of DNA synthesis.
Okazaki fragments: Short segments of DNA that are synthesized on the lagging strand during DNA synthesis; these are later fused by DNA ligase.

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