Return to
Health Education Home Page  

Those Confusing terms...

allele-one of the inherited forms of a particular gene or stretch of DNA. An animal carries two alleles for each gene, one from each parent. AA, Aa, aa, etc.

autosomal-refers to chromosomes other than the sex chromosome.

chromosomes-discrete collections of DNA that contain the information that is passed from one generation to the next. Each animal species has a characteristic number of chromosomes.

crossover-a process that occurs during the creation of eggs and sperm in which chromosomes exchange segments of DNA, enhancing the possible variability in offspring.

epistasis-the process in which one gene cause another(other than its allele)is not to be expressed.

genes-stretches of DNA within a chromosome that contain specific information needed by the cell to make the proteins that control the growth,development, and function of the organism.

genome-the set of DNA molecules that specify the inherited characteristics of an animal. With a few minor exceptions, every cell in an animal's body carries the entire genome within its nucleus.

genotype-the genetic makeup of an organism.

genotyping-the process of identifying which alleles an organism carries for a specific trait or traits.

linkage map-a map that describes the location of genes relative to other genes rather than as points on specific parts of specific chromosomes.

locus (loci)-the location of a particular DNA segment on a chromosome.

marker-a portion of DNA that appears in more than one form in a population, the variations of which can be detected in the laboratory and so used to identify patterns of heredity.

microsatellite-a stretch of DNA that contains a repeating nucleotide pattern, the length of which is polymorphic. Microsatellites are used as markers.

mutation-a change in genetic material.

phenotype-the expressed characteristics of an organism. Not all genes of the genotype affect the phenotype.

polygenic trait-traits controlled by many genes. There are likely to be degrees of a problem rather than all-or-nothing features.

polymerase chain reaction(PCR)-a biochemical technique that allows laboratory workers to produce millions of copies of a relatively short (100-300 nucleotide) sequence of DNA. PCR is an invaluable technique for distinguishing which allele of a microsatellite marker is present in a blood or tissue sample.

polymorphism-one of the various forms of a gene.

quantitative trait loci (QTL)-genes that contribute to the expression of a trait that is expressed on a continuum (e.g., weight gain).

recessive genes-genes that are not expressed in a particular organism. Even though these genes are silent for the time being, they can be passed along to-and expressed in-sucessive generations.

variance-ranges in phenotype that result from genetic and environmental parameters.