Adenine (A)

A purine base that pairs with thymine in the DNA double helix. One of the four DNA bases.

deoxyribonucleic acid (DNA)

information present in a cell that allows it to build a complex multicellular organism. two chains of linked nucleotides in a double helical form are the fundamental substance of which genes are composed.

forward genetics

genetic analysis in which genes are first identified by mutant alleles and mutant phenotypes and later cloned and subjected to molecular analysis


a constricted region of a chromosome that acts as an attachment point to move the chromosome during cell division.


organisms whose nuclei contain two complete copies of the genome and so two identical chromosome sets

functional RNA

an RNA type that plays a role without being translated into protein


the substance of chromosomes; now known to include DNA and chromosomal proteins

DNA cloning

the process of taking a DNA fragment and replicating it many times over until there are many copies so that essentially it can be treated like a reagent in a test tube.


the fundamental physical and functional unit of heredity, which carries information from one generation to the next


a section of RNA (three nucleotides in length) that encodes a single amino acid.


nongenetic chemical changes in histones or DNA that alter gene function without altering the DNA sequence

gene pair

the two copies of a particular type of gene present in a diploid cell (one in each chromosome set)

cytosine (C)

a pyrimidene base that pairs with guanine. one of the four DNA bases


refers to a small specialized fraction of eukaryotic genomes found in mitochondria or chloroplasts

genetic code

a set of correspondences between nucleotide triplets in RNA and amino acids in protein


the study of all aspects of genes and inheritance

model organism

An organism selected for intensive scientific study based on features that make it easy to work with (e.g., body size, life span), in the hope that findings will apply to other species.

reverse genetics

an experimental procedure that begins with a cloned segment of DNA or a protein sequence and uses it (through directed mutagenesis) to introduce programmed mutations back into the genome to investigate function


the entire complement of genetic material in a chromosome set

molecular genetics

the study of the molecular processes underlying gene structure and function

ribonucleic acid (RNA)

a single-stranded nucleic acid similar to DNA but having ribose sugar rather than deoxyribose sugar and uracil rather than thymine as one of the bases


the cloning and molecular characterization of entire genomes


the process that produces a gene or a chromosome set differing from that of the wild type

ribosomal RNA

a class of RNA molecules, encoded in the nucleolar organizer, that have an integral (but poorly understood) role in ribosome structure and function

guanine (G)

a purine base that pairs with cytosine

natural selection

the differential rate of reproduction of different types in a population as the result of different physiological, anatomical, or behavioral characteristics of the types

Southern blot

the transfer of electrophoretically separated fragments of DNA from a gel to an absorbent sheet such as paper; this sheet is then immersed in solution containing a labeled probe that will bind to a fragment of interest


a cell having one chromosome set or an organism composed of such cells

Northern blot

the transfer of electrophoretically separated RNA molecules from a gel onto an absorbent sheet, which is then immersed in a labeled probe that will bind to the RNA of interest.


the tip, or end, of a chromosome

haploid number

the number of chromosomes in the basic genomic set of a species


the basic unit of eukaryotic chromosome structure; a ball of eight histone molecules that is wrapped by two coils of DNA

theory of evolution

all-embracing notion of natural selection acting on variation


a type of basic protein that forms the unit around which DNA is coiled in the nucleosomes of eukaryotic chromosomes


a molecule composed of a nitrogen base, a sugar, and a phosphate group; the basic building block of nucleic acids

thymine (T)

a pyrimidine base that pairs with adenine


a member of a pair of homologous chromosomes

polymerase chain reaction (PCR)

an in vitro method for amplifying a specific DNA segment that uses two primers that hybridize to opposite ends of the segment in opposite polarity and, over successive cycles, prime exponential replication of that segment only.


the synthesis of RNA from a DNA template

homologous chromosomes

chromosomes that pair with each other at meiosis or chromosomes in different species that have retained most of the same genes during their evolution from a common ancestor.

transfer RNA (tRNA)

a class of small RNA molecules that bear specific amino acids to the ribosome in the course of translation


similarity due to shared ancestry from a common ancestor


a chain of linked amino acids; a protein


the ribosome- and tRNA -mediated production of a polypeptide whose amino acid sequence is derived from the codon sequence of an mRNA molecule

messenger RNA

an RNA molecule transcribed from the DNA of a gene; a protein is translated from this RNA molecule by the action of ribosomes


method for detecting specific macromolecules in a mixture that makes use of the specificity of intermolecular binding

Western blot

for protein detection, a protein mixture extracted from cells is separated into bands of distinct proteins by electrophoresis and then blotted onto a membrane

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