the creation of offspring by the fusion of two haploid sex cells (gametes), forming a diploid zygote
the union of the nucleus of a sperm cell with the nucleus of an egg cell, producing a zygote
the entire sequence of stages in the life of an organism, from the adults of one generation to the adults of the next
The complete (haploid) set of an organism's genes; an organism's genetic material.
The creation of offspring by a single parent, without the participation of sperm and egg.
A threadlike, gene-carrying structure found in the nucleus of a eukaryotic cell and most visible during mitosis and meiosis; also, the main gene-carrying structure of a prokaryotic cell. consists of chromatin.
The reproduction of a cell
the fertilized egg, which is diploid, that results from the union of a sperm cell nucleus and an egg cell nucleus
A means of asexual reproduction in which a parent organism, often a single cell, divides into two individuals of about equal size
The complex of DNA and proteins that constitutes eukaryotic chromosomes; often used to refer to the diffuse, very extended form taken by chromosomes when a cell is not dividing.
One of the two identical parts of a duplicated chromosome in a eukaryotic cell
the region of a chromosome where two sister chromatids are joined and where spindle microtubules attach during mitosis and meiosis. divids at the onset of anaphase during mitosis and anaphase II during meiosis
an ordered sequence of events (including interphase and the mitotic phase) that extends from the time a eukaryotic cell is first formed from a dividing parent cell until its own division into two cells
The period in the eukaryotic cell cycle when the cell is not actually dividing.
mitotic phase (M phase)
The part of the cell cycle when mitosis divides the nucleus and distributes its chromosomes to the daughter nuclei and cytokinesis divides the cytoplasm, producing two daughter cells
The division of a single nucleus into two genetically identical daughter nuclei. This and cytokinesis make up the mitotic (M) phase of the cell cycle.
division of the cytoplasm to form two separate daughter cells. This usually occurs during telophase of mitosis, and mitosis and this make up the mitotic (M) phase of the cell cycle
the first stage of mitosis, during which the chromatin condenses to form structures (sister chromatids) visible with a light microscope and the mitotic spindle begins to form, but the nucleus is still intact.
The second stage of mitosis, during which the nuclear envelope fragments and the spindle microtubules attach to the kinetochores of the sister chromatids
the third stage of mitosis, during which all the cell's duplicated chromosomes are lined up at an imaginary plane equidistant between the poles of the mitotic spindle.
the fourth stage of mitosis, beginning when sister chromatids separate from each other and ending when a complete set of daughter chromosomes have arrived at each of the two poles of the cell
The fifth and final stage of mitosis, during which daughter nuclei form at the two poles of a cell. usually occurs together with cytokinesis.
A spindle-shaped structure formed of microtubules and associated proteins that is involved in the movements of chromosomes during mitosis and meiosis (shaped roughly like a football)
material in the cytoplasm of a eukaryotic cell that gives rise to microtubules; important in mitosis and meiosis; also called microtubule-organizing center
the first sign of cytokinesis during cell division in an animal cell; a shallow groove in the cell surface near the old metaphase plate
A double membrane across the midline of a dividing plant cell, between which the new cell wall forms during cytokinesis
The requirement that to divide, a cell must be attached to a solid surface
The arrest of cell division that occurs when cells grown in a laboratory dish touch one another; generally due to an inadequate supply of growth factor
A protein secreted by certain body cells that stimulates other cells to divide.
cell cycle control system
A cyclically operating set of proteins that triggers and coordinates events in the eukaryotic cell cycle
a cell that is not subject to normal cell cycle control mechanisms and that will therefore divide continuously
an abnormal mass of cells that forms within otherwise normal tissue
an abnormal mass of cells that remains at its original site in the body
an abnormal tissue mass that can spread into neighboring tissue and to other parts of the body; a cancerous tumor
The spread of cancer cells beyond their original site
Cancer that originates in the coverings of the body, such as skin or the lining of the intestinal tract.
cancer of the supportive tissues, such as bone, cartilage, and muscle
a type of cancer of the blood-forming tissues, characterized by an excessive production of white blood cells and an abnormally high number of them in the blood; cancer of the bone marrow cells that produce leukocytes.
cancer of the tissues that form white blood cells
Any cell in a multicellular organism except a sperm or egg cell or a cell that develops into a sperm or egg
The two chromosomes that make up a matched pair in a diploid cell. are of the same length, centromere position, and staining pattern and possess genes for the same characteristics at corresponding loci. One is inherited from the organism's father, the other from the mother.
The particular site where a gene is found on a chromosome. Homologous chromosomes have corresponding gene _________
A chromosome that determines whether an individual is male or female
a chromosome not directly involved in determining the sex of an organism; in mammals, for example, any chromosome other than X or Y
in an organism that reproduces sexually, a cell containing two homologous sets of chromosomes, one set inherited from each parent; a 2n cell
A sex cell; a haploid egg or sperm. The union of two of these, of opposite sex (fertilization) and produces a zygote.
in the life cycle of an organism that reproduces sexually, a cell containing a single set of chromosomes; an n cell
In a sexually reproducing organism, the division of a single diploid nucleus into four haploid daughter nuclei. This and cytokinesis produce haploid gametes from diploid cells in the reproductive organs of the parents
the exchange of segments between chromatids of homologous chromosomes during synapsis in prophase I of meiosis; also, the exchange of segments between DNA molecules in prokaryotes
The microscopically visible site where crossing over has occurred between chromatids of homologous chromosomes during prophase I of meiosis
the production, by crossing over and/or independent assortment of chromosomes during meiosis, of offspring with allele combinations different from those in the parents. the term may also be used more specifically to mean the production by crossing over of eukaryotic or prokaryotic chromosomes with gene combinations different from those in the original chromosomes.
A display of micrographs of the metaphase chromosomes of a cell, arranged by size and centromere position
Down syndrome; an extra chromosome 21
a human genetic disorder resulting from the presence of an extra chromosome 21; characterized by heart and respiratory defects and varying degrees of mental retardation
an accident of meiosis or mitosis in which a pair of homologous chromosomes or a pair of sister chromatids fail to separate at anaphase
the loss of one or more nucleotides from a gene by mutation; the loss of a fragment of a chromosome.
repetition of part of a chromosome resulting from fusion with a fragment from a homologous chromosome; can result from an error in meiosis or from mutagenesis
a change in a chromosome resulting from reattachment of a chromosome fragment to the original chromosome, but in a reverse direction. mutagens and errors during meiosis can cause this.
(1) During protein synthesis, the movement of a tRNA molecule carrying a growing polypeptide chain from the A site to the P site on a ribosome. (The mRNA travels with it.) (2) A change in a chromosome resulting from a chromosomal fragment attaching to a nonhomologous chromosome; can occur as a result of an error in meiosis or from mutagenesis.
The scientific study of heredity and hereditary variations
The fusion of sperm and egg produced by the same individual organism.
The fusion of sperm and egg derived from two different individuals
Referring 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
The offspring of parents of two different species or of two different varieties of one species; the offspring of two parents that differ in one or more inherited traits; an individual that is heterozygous for one or more pairs of genes.
another word for hybrid
The parent individuals from which offspring are derived in studies of inheritance; P stands for parental.
the offspring of two parental (P generation) individuals; F1 stands for first filial
the offspring of the f1 generation; F2 stands for second filial.
An experimental mating of individuals differing at one genetic locus
an alternative form of a gene
having two identical alleles for a given gene
having two different alleles for a given gene
In a heterozygote, the allele that determines the phenotype with respect to a particular gene
in a heterozygous individual, the allele that has no noticeable effect on the phenotype
law of segregation
A general rule in inheritance that individuals have two alleles for each gene and that when gametes form by meiosis, the two alleles separate, and each resulting gamete ends up with only one allele of each gene; also known as Mendel's first law of inheritance
A diagram used in the study of inheritance to show the results of random fertilization.
The expressed traits of an organism
The genetic makeup of an organism
An experimental mating of individuals differing at two genetic loci
law of independent assortment
A general rule in inheritance that when gametes form during meiosis, each pair of alleles for a particular characteristic segregate independently of other pairs; also known as Mendel's second law of inheritance.
the mating between an individual of unknown genotype for a particular characteristic and an individual that is homozygous recessive for that same characteristic
rule of multiplication
A rule stating that the probability of a compound event is the product of the separate probabilities of the independent events
rule of addition
A rule stating that the probability that an event can occur in two or more alternative ways is the sum of the separate probabilities of the different ways.
a family tree representing the occurrence of heritable traits in parents and offspring across a number of generations
A genetic disease that occurs in people with two copies of a certain recessive allele; characterized by an excessive secretion of mucus and vulnerability to infection; fatal if untreated.
mating between close relatives
A form of human dwarfism caused by a single dominant allele; the homozygous condition is lethal
A human genetic disease caused by a dominant allele; characterized by uncontrollable body movements and degeneration of the nervous system; usually fatal 10 to 20 years after the onset of symptoms.
A technique for diagnosing genetic defects while a fetus is in the uterus. A sample of amniotic fluid, obtained by a needle inserted into the amnion, is analyzed for telltale chemicals and defective fetal cells.
chorionic villus sampling (CVS)
A technique for diagnosing genetic defects while the fetus is in an early development stage within the uterus. A small sample of the fetal portion of the placenta is removed and analyzed.
A technique for examining a fetus in the uterus. High-frequency sound waves echoing off the fetus are used to produce an image of the fetus.
A type of inheritance in which the phenotypes of the heterozygote and dominant homozygote are indistinguishable.
A type of inheritance in which the phenotype of a heterozygote (Aa) is intermediate between the phenotypes of the two types of homozygotes (AA and aa).
ABO blood group
genetically determined classes of human blood that are based on the presence or absence of carbohydrates A and B on the surface of red blood cells; the phenotypes, also called blood types, are A, B, AB, and O
inheritance pattern in which a heterozygote expresses the distinct trait of both alleles
the control of more than one phenotypic characteristic by a single gene
The additive effect of two or more gene loci on a single phenotypic characteristic.
chromosome theory of inheritance
A basic principle in biology stating that genes are located on chromosomes and that the behavior of chromosomes during meiosis accounts for inheritance patterns.
genes located on the same chromosome that tend to be inherited together in genetic crosses
With respect to two given genes, the number of recombinant progeny from a mating divided by the total number of progeny. Recombinant progeny carry combinations of alleles different from those in either of the parents as a result of independent assortment of chromosomes or crossing over
a gene located on a sex chromosome
Red-green color blindness
A category of common, sex-linked human disorders involving several genes on the X chromosome; characterized by a malfunction of light-sensitive cells in the eyes; affects mostly males but also homozygous females.
A human genetic disease caused by a sex-linked recessive allele; characterized by excessive bleeding following injury.
Duchenne muscular dystrophy
A human genetic disease caused by a sex-linked recessive allele; characterized by progressive weakening and a loss of muscle tissue.
the study of the molecular basis of genes and gene expression; molecular genetics
A virus that infects bacteria; also called a phage.
another name for a bacteriophage
An organic monomer consisting of a five-carbon sugar covalently bonded to a nitrogenous base and a phosphate group. The building blocks of nucleic acids.
a polymer made up of many nucleotides covalently bonded together
The alternating chain of sugar and phosphate to which the DNA and RNA nitrogenous bases are attached
A single-ring nitrogenous base found in DNA; forms hydrogen bonds or is paired with adenine.
A single-ring nitrogenous base found in DNA and RNA; forms hydrogen bonds or is paired with guanine
A double-ring nitrogenous base found in DNA and RNA; forms hydrogen bonds or is paired with thymine
A double-ring nitrogenous base found in DNA and RNA; forms hydrogen bonds or is paired with cytosine
A single-ring nitrogenous base found in RNA; forms hydrogen bonds or is paired with adenine. Only found in RNA.
The form of native DNA, referring to its two adjacent polynucleotide strands wound into a spiral shape.
Type of DNA replication in which the replicated double helix consists of one old strand, derived from the old molecule, and one newly made strand.
An enzyme that assembles DNA nucleotides into polynucleotides using a preexisting strand of DNA as a template.
an enzyme, essential for DNA replication, that catalyzes the covalent bonding of adjacent DNA nucleotides; used in genetic engineering to paste a specific piece of DNA containing a gene of interest into a bacterial plasmid or other vector
The synthesis of RNA on a DNA template
The synthesis of a polypeptide using the genetic information encoded in an mRNA molecule. There is a change of "language" from nucleotides to amino acids.
A set of three-nucleotide-long words that specify the amino acids for polypeptide chains
a three-nucleotide sequence in mRNA that specifies a particular amino acid or termination signal; the basic unit of the genetic code
the set of rules giving the correspondence between nucleotide triplets (codons) in mRNA and amino acids in proteins
enzyme that links together the growing chain of RNA nucleotides during transcription, using a DNA strand as a template
a specific nucleotide sequence in DNA, located at the start of a gene, that is the binding site for RNA polymerase and the place where transcription begins
A special sequence of nucleotides in DNA that marks the end of a gene. It signals RNA polymerase to release the newly made RNA molecule, which then departs from the gene
messenger RNA (mRNA)
The type of ribonucleic acid that encodes genetic information from DNA and conveys it to ribosomes, where the information is translated into amino acid sequences
in eukaryotes, a nonexpressed (noncoding) portion of a gene that is excised from the RNA transcript.
In eukaryotes, a coding portion of a gene.
The removal of introns and joining of exons in eukaryotic RNA, forming an mRNA molecule with a continuous coding sequence; occurs before mRNA leaves the nucleus.
transfer RNA (tRNA)
A type of ribonucleic acid that functions as an interpreter in translation. Each has a specific anticodon, picks up a specific amino acid, and conveys the amino acid to the appropriate codon on mRNA.
on a tRNA molecule, a specific sequence of three nucleotides that is complementary to a codon triplet on mRNA
ribosomal RNA (rRNA)
The type of ribonucleic acid that, together with proteins, makes up ribosomes; the most abundant type of RNA
on mRNA, the specific three-nucleotide sequence (AUG) to which an initiator tRNA molecule binds, starting translation of genetic information.
One of two of a ribosome's binding sites for tRNA during translation. Holds the tRNA carrying the growing polypeptide chain. (stands for peptidyl tRNA.)
one of two of a ribosome's binding sites for tRNA during translation. Holds the tRNA carrying the next amino acid to be added to the polypeptide chain. (stands for aminoacyl tRNA)
the anticodon of an incoming tRNA molecule, carrying its amino acid, pairs with the mRNA codon in the A site of the ribosome
peptide bond formation
the polypeptide separates from the tRNA to which it was bound (the one in the P site) and attaches by a peptide bond to the amino acids carried by the tRNA in the A site. the ribosome catalyzes formation of the bond. thus, one more amino acid is added to the chain
In mRNA, one of three triplets (UAG, UAA, UGA) that signal gene translation to stop.
a change in the nucleotide sequence of DNA; the ultimate source of genetic diversity
the way in which a cell's mRNA-translating machinery groups the mRNA nucleotides into codons.
The creation of a mutation
a chemical or physical agent that interacts with DNA and causes a mutation
The protein shell that encloses a viral genome. It may be rod-shaped, polyhedral, or more complex in shape.
A type of viral replication cycle resulting in the release of new viruses by lysis (breaking open) of the host cell.
A type of bacteriophage replication cycle in which the viral genome is incorporated into the bacterial host chromosome as a prophage. New phages are not produced, and the host cell is not killed or lysed unless the viral genome leaves the host chromosome.
phage DNA that has inserted by genetic recombination into the DNA of a prokaryotic chromosome.
A virus that has appeared suddenly or has recently come to the attention of medical scientists.
an enzyme that catalyzes the synthesis of DNA on an RNA template.
A RNA virus that produces by means of a DNA molecucle; it 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 and a number of cancer-causing viruses are this
acquired immunodeficiency syndrome; The name of the late stages of HIV infection; defined by a specified reduction of T cells and the appearance of characteristic secondary infections.
human immunodeficiency virus, the retrovirus that attacks the human immune system and causes AIDS
The incorporation of new genes into a cell from DNA that the cell takes up from the surrounding environment.
The transfer of bacterial genes from one bacterial cell to another by a phage
The union (mating) of two bacterial cells or protist cells and the transfer of DNA between the two cells.
A piece of DNA that can exist as a bacterial plasmid. carries genes for making sex pili and other structures needed for conjugation, as well as a site where DNA replication can start. F stands for fertility.
a small ring of DNA separate from the chromosome(s). found in prokaryotes and yeast.
A bacterial plasmid that carries genes for enzymes that destroy particular antibiotics, thus making the bacterium resistant to the antibiotics