Allowing some substances to pass; permeable to smaller molecules but not to larger ones
The gradual difference in the concentration of solutes in a solution between two regions
A substance that is dissolved in a solution
The dissolving agent in a solution
The spontaneous movement of particles from where they are more concentrated to where they are less concentrated.
Occurs when two opposing processes proceed at the same rate (e.g. when the number of people ascending a slope on a ski lift = the number of people skiing down the slope).
The diffusion of water across a selectively permeable membrane.
Phrase used to describe the cell membrane. (See page 80).
The passage of a substance across a biological membrane down its concentration gradient, aided by specific transport proteins. (See page 82).
A solution having the same solute concentration as another solution. (See page 83).
In comparing two solutions, the one with the greater concentration of solutes. (See page 83)
In comparing two solutions, the one with the lower concentration of solutes. (See page 83)
The control of water balance. (See page 83)
The diffusion of a substance across a biological membrane, without any input of energy.
The movement of a substance across a biological membrane against its conentration gradient, aided by specific transport proteins and requiring input of energy (often as ATP).
Cellular "drinking"; a type of endocytosis in which the cell takes fluid and dissolved solutes into small membranous vesicles.
Cellular "eating"; a type of endocytosis whereby a cell engulfs macromolecules, other cells, or particles into its cytoplasm.
The movement of materials into the cytoplasm of a cell via membranous vesicles or vacuoles.
The movement of materials out of the cytoplasm of a cell via membranous vesicles or vacuoles.
Refers to the process in which the cell membrane pulls away from the cell wall as a plant cell loses water (p. 83).
Describes the tendency of a cell in a given solution to lose or gain water (p. 83).
Limp. Lacking in stiffness or firmness, as in a plant cell in surroundings where there is no tendency for water to enter the cell (p. 83).
Means "swollen or distended", especially by fluids, as in plant cells (p. 83).
Refers to the bursting of an animal cell when placed in an extremely hypotonic solution (p. 83).
The process by which a cell divides into two new daughter cells (p. 127).
Threadlike structure within the nucleus containing the genetic information that is passed from one generation of cells to the next; a typical human body cell has 46 of these (p. 126).
One of two identical "sister" parts of a duplicated chromosome (p. 128).
Area where the chromatids of a chromosome are attached to one another; forms a narrow "waist" (p. 128).
The series of events that cells go through as they grow and divide (p. 129).
Period of the cell cycle between cell divisions (p. 129).
A period during interphase in which cells do most of their growing--increasing in size and synthesizing new proteins and organelles (p. 129).
Period of time during interphase in which chromosomes are replicated and the synthesis of DNA takes place (p. 129).
Period of time during interphase--usually the shortest--during which many of the organelles and molecules required for cell division are produced (p. 129).
This part of the cell cycle is divided into four phases: prophase, metaphase, anaphase, and telophase (p. 129).
During this phase of mitosis the chromosomes become visible, the nucleolus disappears, and the nuclear envelope breaks down (p. 130).
A fanlike microtubule structure that helps to separate the chromosomes (p. 130-131).
During this phase of mitosis the chromosomes line up across the center of the cell (p. 131).
During this phase of mitosis the centromeres split, allowing the chromatids to be pulled to opposite sides of the cell (p. 131).
During this phase of mitosis the chromosomes unwind to form chromatin, a nuclear envelope re-forms around the chromosomes, and a nucleolus becomes visible in each daughter nucleus (p. 131).
The division of the cytoplasm itself; in animal cells the cell membrane is drawn inward to pinch the cytoplasm into two parts while in plants a cell plate forms between the daughter nuclei (p. 129-132).
Term used to refer to chromosomes that each have a corresponding chromosome from the opposite-sex parent (p. 136).
A mnemonic (memory aid) that can be used to remember the stages of the cell cycle: Interphase, Prophase, Metaphase, Anaphase, Telophase (p. 130-131).
The normal number of chromosomes in a typical cell of the human body.
Clouds of cytoplasmic material from which spindle microtubules emerge; in animals these contain centrioles. These are also known as microtubule-organizing centers (p. 131).
A protein structure on each chromatid located at the centromere region to which spindle microtubules attach (p. 130-131)
The precursor of a new plant cell wall that forms during cell division and divides a cell into two (p.132).
A shallow groove in the surface of an animal cell; the first sign of cleavage (cytokinesis) (p. 132).
An imaginary plane equidistant between the two poles of the spindle along which the centromeres of the chromosomes line up during metaphase (p. 131).
Structure that carries the genes; made of protein and DNA.
A "picture" of chromosomes arranged by size and centromere location that can reveal certain abnormalities.
An accident of meiosis or motosis, in which both members of a pair of homologous chromosomes or both sister chromatids fail to move apart properly.
The region of a chromosome where two sister chromatids are joined and where spindle microtubules attach during mitosis and meiosis.
The repetitive DNA at each end of a eukaryotic chromosome.
Chromosomal abnormality characterized by only one X chromosome; affected individuals are relatively normal, but may be short, sexually underdeveloped, and infertile.
Affected individuals have three of chromosome 13; trisomy 13.
Affected individuals have three of chromosome 18; trisomy 18. Affected individuals appear thin and frail, they fail to thrive, and have difficulty feeding.
Affected individuals have three of chromosome 21; trisomy 21. Affected individuals have short stature, heart defects, and mental retardation. Risk of having a child with this increases with maternal age.
The result of losing a part of chromosome #5; affected individuals have a catlike cry and severe mental retardation.
The inactive X chromosome in a female cell; de-activation of one X-chromosome happens early in embryonic development at random in mammals.
The two chromosomes that make up a matched pair in a diploid cell; two chromosomes that have the same length, centromere position, and possess the same genes; one of the two chromosomes is inherited from the mother, the other from the father.
Any chromosome other than a sex chromosome.
Extraction of amniotic fluid from a pregnant woman to aid in the diagnosis of fetal abnormalities.
The passing of traits from parents to offspring (p. 152).
The branch of biology that studies heredity (p. 152).
A cross that involves one pair of contrasting traits (p. 156).
Refers to organisms for which sexual reproduction produces offspring with inherited traits identical to those of the parents; the organisms are homozygous for the characteristics under consideration (p. 155).
Alternative versions of a gene (p. 156).
One form of a hereditary trait that prevents the recessive trait from showing up (p. 156).
Two alleles of a particular gene present in an individual are the same (p. 156).
The set of allleles that an individual has; an individual's genetic make-up (p. 157).
The physical appearance of a trait (p. 157).
law of segregation
The two alleles for a trait separate when gametes are formed; explained by the fact that alleles for a trait are on homologous chromosomes, which separate during meiosis (p. 156).
law of independent assortment
The alleles of different genes separate independently of one another during gamete formation (p. 158).
Describes an individual with two recessive alleles for a trait; for instance, a pea plant with "pp," resulting in white flowers (p. 156).
Describes an individual with a copy of the dominant and recessive alleles for a trait; for instance, a pea plant with "Pp," resulting in purple flowers (p. 156).
Describes an individual with two dominant alleles for a trait; for instance, a pea plant with "PP," resulting in purple flowers (p. 156).
A diagram used to predict the expected outcomes of a genetic cross (p. 157).
A cross that involves two pairs of contrasting traits (p. 158).
A cross in which an individual whose phenotype is dominant, but whose genotype is not known, is crossed with a homozygous recessive individual (p. 159).
A trait influenced by several genes; the genes may be scattered along the same chromosome or located on different chromosomes (p. 169).
When an individual displays a trait that is intermediate between the two parents; causes an intermediate phenotype (p. 166).
When two dominant alleles are expressed at the same time; Roan coats in horses is an example (p. 167).
The first set of parents crossed in which their genotype is the basis for predicting the genotype of their offspring (p. 155).
The first generation of offspring which results after mating or genetically crossing two types of parents with different genotypes or phenotypes (p. 155).
The second filial generation; the offspring of the F-1 generation when the F-1 generation is selfpollinated or when two individuals from the F-1 generation are crossed (p. 155).
The offspring of crosses between parents with different traits; these individuals will be heterozygous (p. 155).
Sequence of DNA that codes for a protein and thus determines a trait (p. 47).
Specialized cell involved in sexual reproduction; "sex cell" (p. 137).
Refers to genes that have more than two alleles; ABO blood types in humans is an example. (Remember, any one individual can only have two of those alleles. See p. 167).
Austrian monk who discovered the basic principles of heredity by breeding garden peas in carefully planned experiments (p. 154).
rule of addition
The probability that an event can occur in two or more alternative ways is the sum of the separate probabilities (p. 160).
rule of multiplication
The probability of a compound event (such as two quarters both turning up heads when both are tossed) is the product of the separate probabilities of the independent event (p. 160).
A family tree representing the occurrence of heritable traits in parents and offspring across a number of generations (p. 161).
An individual who is heterozygous for a recessively inherited disorder and who therefore does not show symptoms of that disorder (p. 161).
Genetic disorder characterized by an excessive secretion of very thick mucus from the lungs, pancreas, and other organs; the most common lethal genetic disease in the U.S.; 1 in 25 Caucasians are carriers (p. 162).
A serious disorder caused by a dominant allele characterized by a normal head and torso but abnormally short arms and legs (p. 163).
A degenerative disorder of the nervous system that usually does not begin until middle age; causes uncontrollable movements in all parts of the body, memory loss, and impaired judgment (p. 163).
A technique for diagnosing genetic defects while a fetus is in the uterus. A sample of amniotic fluid, obtained via a needle, is analyzed for telltale chemicals and defective fetal cells (p. 164).
chorionic villus sampling
A technique for diagnosing genetic defects while the fetus is in the uterus. A small sample of the fetal portion of the placenta is removed and analyzed (p. 165).
Sound waves are used to produce a picture of the fetus (p. 165).
The control of more than one phenotypic characteristic by a single gene; most genes, in fact, influence multiple characteristics (p. 168).
chromosome theory of inheritance
States that genes occupy specific loci (positions) on chromosomes and that it is the chromosomes that undergo segregation and independent assortment during meiosis (p. 171).
Refers to a gene located on either sex chromosome, although in humans the term has historically referred specifically to a gene on the X-chromosome (p. 176).
Red-green color blindness
A common sex-linked disorder characterized by a malfunction of light sensitive cells in the eyes (p. 177).
A sex-linked recessive trait characterized by the absence of one or more of the proteins required for blood clotting (p. 177).
Duchenne muscular dystrophy
A sex-linked recessive disorder characterized by a progressive weakening of the muscles and loss of coordination; affected individuals rarely live past their early 20s (p. 177).
Refers to genes located close together on the same chromosome, which tend to be inherited together; these genes do not follow Mendel's law of independent assortment (p. 172).
Name given to bacterial viruses; literally, means "bacteria eaters" (p. 182).
Shortened name for viruses that infect bacteria (p. 182).
Name given to the monomers that make up nucleic acids (DNA and RNA); consists of a nitrogenous base, a sugar, and a phosphate group (p. 184).
A model for DNA replication in which each half of an original DNA molecule serves as a template for and is maintained in each daughter molecule (p. 188).
The transfer of genetic information from DNA into an RNA molecule (p. 190).
The transfer of the information in RNA into a protein (p. 190).
A three nucleotide sequence in mRNA hat specifies a particular amino acid; the basic unit of the genetic code (p. 191).
An enzyme that links together RNA nucleotides (p. 193).
A sequence of bases in the DNA template that signals the end of a gene and that triggers the release of RNA polymerase from the RNA molecule and the gene (p. 193).
The kind of RNA that encodes amino acid sequences; the molecule that conveys genetic information from DNA to the translation machinery of the cell (p. 194).
Picks up a specific amino acid and conveys it to the appropriate codon on the mRNA (p. 194).
A special triplet of bases at one end of a tRNA molecule that is complementary to a codon triplet on mRNA (p. 195).
An organelle consisting of two subunits (one larger, one smaller), each made up of proteins and rRNA; coordinates mRNA and tRNA to enable the formation of polypeptides (p. 196).
The "start" codon; codes for the amino acid methionine (p. 197).
Name given to any change in the nucleotide sequence of DNA (p. 199).
The replacement of one nucleotide with another; a form of point mutation (p. 199).
The insertion of a new base into a base sequence; results in a "frame shift" (p. 199).
The deletion of a base from a sequence of bases; results in a "frame shift" (p. 199).
Name given to a triplet grouping (codon); base insertions or deletions may change this - resulting in all nucleotides "downstream" being regrouped into new codons (p. 199).
The production of mutations either spontaneously or through exposure to physical or chemical agents (p. 199).
A name given to a physical or chemical agent that causes mutations (p. 199).
The protein coat of a virus (p. 200).
Viral DNA replication occurs without destroying the host cell (p. 200).
Viral replication results in the lysis (breaking open) of the host cell and the release of the viruses that were produced within the cell (p. 200).
An enzyme that catalyzes the synthesis of DNA on an RNA template; enzyme found in retroviruses (p. 203).
Acquired Immune Deficiency Syndrome (p. 203).
Human Immunodeficiency Virus; viral cause of AIDS (p. 203).
An RNA virus that reverse-transcribes its RNA into DNA, inserts the DNA into a cellular chromosome, and then transcribes more copies of the RNA from the viral DNA; HIV is an example (p. 203).
Genetic change in a population or species over generations; all the changes that transform life on Earth; the heritable changes that have produced Earth's diversity of organisms.
descent with modification
The idea that all organisms are descended from a single ancestor.
Explains current observations and predicts new observations.
An inherited characteristic that enhances an organism's ability to survive and reproduce in a particular environment.
Structures that are similar in different species of common ancestry.
A change in a population's gene pool over a succession of generations; evolutionary changes in species over relatively brief periods of geologic time.
A comprehensive theory of evolution that incorporates genetics and includes most of Darwin's ideas, focusing on populations as the fundamental units of evolution.
A change in the nucleotide sequence of DNA; the ultimate source of genetic diversity.
Differential success in reproduction by different phenotypes resulting from interactions with the environment.
A group whose members possess similar anatomical characteristics and have the ability to interbreed.
Jean Baptiste Lamarck
Proposed that acquired characteristics were inheritable.
Argued that human overpopulation would lead to decreasing living standards if left unchecked; plants and animals produce more offspring than can survive; influenced Darwin's thinking on Natural Selection.
Popularized Uniformitarianism--the idea that natural forces in the past are the same as today; influenced Darwin's thinking on Natural Selection.
Natural forces in the past, such as erosion and sedimentation, are the same as today; gradual change over long periods of time have shaped many of the geological features of the planet.
The relative ability of an organism to survive and transmit its genes to the next generation.
The entire collection of genes among a population of organisms.
The study of gene pools and their changes.
A structure of marginal, if any, importance to an organism; historical remnants of structures that had important functions in ancestors.
The study of differences in chemicals and chemical processes among species.
The branch of embryology that compares the development of embryos of two or more species.
Studies the similarities and differences between the genes of different species to determine how closely related they are.
Physical features of an organism--shape, body covering, skeletal structure, etc.--that improve its ability to survive and reproduce.
Biochemical features of an organism--digestive enzymes, for instance--that improve its ability to survive and reproduce.
Inherited behaviors or an inherited tendency to learn specific behaviors that improve an organism's ability to survive and reproduce.