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Deoxyribonucleic acid, the material that contains the information that determines inherited characteristics.


Ribonucleic acid, a natural polymer that is present in all living cells and that plays a role in protein synthesis.


An organic compound that consists of a sugar, a phosphate, and a nitrogenous base; the basic building block of a nucleic-acid chain.


The most basic phyiscal unit of heredity; a segment of nucleic acids that codes for a functional unit of RNA and/or a protein.


In a eukaryotic cell, one of the structures in the nucleus that are made up of DNA and protein; in a prokaryotic cell, the main ring of DNA.


The substance that composes eukaryotic chromosomes; it consists of specific proteins, DNA, and small amounts of RNA.


Characterized by the capacity for precise pairing of purine and pyridimine bases between strands of DNA and sometimes RNA such that the structure of one strand determines the other.


The process that makes an exact copy of DNA.

sister chromatids

Two identical copies of a chromatin connected by a centromere.


The region of the chromosome that holds the two sister chromatids together during mitosis.


A network of microtubules that forms during mitosis and moves chromatids to the poles.


A small, cylindrical cell organelle, seen near the nucleus in the cytoplasm of most eukaryotic cells, that divides in perpendicular fashion during mitosis


In eukaryotic cells, a process of cell divison that forms two new nuclei, each of which has the same number of chromosomes.


The division of the cytoplasm of a cell; follows the division of the cell's nucleus by mitosis or meiosis.


A type of disorder or cell growth that results in invasion and destruction of surrounding healthy tissue by abnormal cells.

cell cycle

The life cycle of a cell; in eukaryotes, it consists of a cell-growth period in which DNA is synthesized and a cell-division period in which mitosis takes place.


The first stage of mitosis or meiosis in eukaryotic cell division, during which the nuclear envelope breaks down and strands of chromatin form into chromosomes.


The stage in mitosis or meiosis in which the duplicated chromosomes line up along the equatorial plate of the spindle.


The stage in mitosis or meiosis following metaphase in which the daughter chromosomes move away from each other to opposite ends of the cell.


The final stage of meiosis or mitosis, in which the separated chromosomes reach the opposite poles of the dividing cell and the nuclei of the daughter cells form around the two sets of chromosomes.


The portion of protein synthesis that takes place at ribosomes and that uses the codons in mRNA molecules to specify the sequence of amino acids in polypeptide chains.


The process of forming a nucleic acid by using another molecule as a template; particularly the process of synthesizing RNA by using one strand of a DNA molecule as a template.


A set of three.


In DNA and mRNA, a three-nucleotide sequence that encodes an amino acid or signifies a start signal or a stop signal.


In region of a tRNA molecule that consists of a sequence of three bases that is complementary to an mRNA codon.


A chain of amino acids linked together by peptide bonds.

amino acid

A compound of a class of simple organic compounds that contain a carboxyl group and an amino group and that combine to form proteins.


A nucleotide sequence that is part of a gene and that is transcribed from DNA into mRNA but not translated into amino acids.


One of several nonadjacent nucleotide sequences that are part of one gene and that are transcribed, joined together, and then translated.


A cell that contains two haploid sets of chromosomes.


Describes a cell, nucleus, or organism that has only one set of unpaired chromosomes.

crossing over

The exchange of genetic material between homologous chromosomes during meiosis; can result in genetic recombination.


The science of heredity and of the mechanisms by which traits are passed from parents to offspring.


One of the alternative forms of a gene that governs a characteristic, such as hair color.


A haploid reproductive cell that unites with another haploid reproductive cell to form a zygote.


The union of a male and female gamete to form a zygote.


The cell that results from the fusion of gametes; a fertilized egg.


An organism, cell, or piece of genetic material that is genetically identical to one from which it was derived; to make a genetic duplicate.

true breeding

Describes organisms or genotypes that are homozygous for a specific trait and thus always produce offspring that have the same phenotype for that trait.


In biology, the offspring of a cross between parents that have differing traits; a cross between individuals of different species, subspecies, or varieties.


Describes an individual that has identical alleles for a trait on both homologous chromosomes.


Describes an individual that carries two different alleles of a gene.


The entire genetic makeup of an organism; also the combination of genes for one or more specific traits.


An organism's appearance or other detectable characteristic that results from the organism's genotype and the environment.

multiple alleles

More than two alleles (versions of the gene) for a genetic trait.

polygenic trait

A trait that is influenced by more than one gene.


An abnormal condition of having more than two sets of chromosomes.

DNA fingerprint

A pattern of DNA characteristics that is unique, or nearly so, to an individual organism.

gel electrophoresis

A technique for separating protein molecules of varying sizes in a mixture by moving them through a block of gel, as of agarose or polyacrylamide, by means of an electric field, with smaller molecules moving faster and therefore farther than larger ones.

restriction enzyme

An enzyme that cuts double-stranded DNA into fragments by recognizing specific nucleotide sequences and cutting the DNA at those sequences.

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