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Genetic Glossary
ALLELES: One member of a pair or series of genes that occupy a specific position on a specific chromosome..
ARTIFICIAL MUTATION: A Hybrid. The offspring of genetically dissimilar parents or stock, especially the offspring produced by breeding plants or animals of different varieties, species, or races.
AUTOSOME: A chromosome that is not a sex chromosome or any chromosome except the gender, sex chromosome. Also called EUCHROMOSOME.
AVICULTURE: The breeding, raising and care of birds.
BACKCROSS: To cross (a hybrid) with one of its parents or with an individual genetically identical to one of its parents. If the parent is a homozygous-recessive, this is known as a test cross.
BASE SEQUENCE: The original sequence.
CELL: The smallest structural unit of an organism that is capable of independent functioning, consisting of one or more nuclei, cytoplasm, and various organelles, all surrounded by a semi permeable cell membrane. Also a container for chromosomes or the building blocks of an individual. A pigeon cell carries at least 40 chromosomes in a gamete cell or at least 80 chromosomes (40 pairs) in all other cells.
CHIASMA: see also CROSSOVER: The point of contact between paired chromatids during meiosis, resulting in a cross-shaped configuration and representing the cytological manifestation of crossing over. Or more simply put - When pair of chromosomes trades genes.
CHROMATID: Either of the two daughter strands of a replicated chromosome that are joined by a single centromere and separate during cell division to become individual chromosomes. Or Either of the two fibrils formed by replication of the chromosome pair prior to meiosis or mitosis.
CHROMOSOME: A threadlike linear strand of DNA and associated proteins in the nucleus of eukaryotic cells that carries the genes and functions in the transmission of hereditary information. Many genes linked together in a string. Chromosomes come in pairs in all cells except gamete cells. Also a circular strand of DNA in bacteria, that contains the hereditary information necessary for cell life.
CHROMOSOME PAIR: Two chromosomes of the same type of which one coming from the female parent, the other came from the male parent. A pigeon carries at least 41 such chromosome pairs.
CIS LINKAGE: Two or more genes that are on the same chromosome. See also coupling.
CISTRON: A section of DNA that contains the genetic code for a single polypeptide and functions as a hereditary unit. Also a gene. The smallest unit of viable genetic material. A unit whose function is lost if not present in its entirety
CO DOMINANCE: An allele that causes the homozygous form to look different than wild type and the heterozygous form to have traits of both so that all three look different from each other; or a condition in which both alleles of a gene pair in a heterozygote are fully expressed, with neither one being dominant or recessive to the other. Also referred to as partial dominance, incomplete dominance, lack or absence of dominance intermediate dominance, imperfect dominance, egalitarian dominance, non-dominance and transdominance. Co dominance is the preferred term
COMPLETE DOMINANCE or DOMINANT, which is the preferred term: An allele that causes the homozygous form and the heterozygous form to look the same as each other, but different than wild type.
COUPLING: Two or more genes that are on the same chromosome.
CROSSOVER: see also CRIASMA: A characteristic resulting from the exchange of genetic material between homologous chromosomes during meiosis. Or when a pair of chromosomes trades genes. One of the processes that make gamete cells unique.
CYTOLOGICAL: The branch of biology that deals with the formation, structure, and function of cells.
DIPLOID: All cells are diploid except gametes, which are haploid. Or Having a pair of each type of chromosome, so that the basic chromosome number is doubled: diploid somatic cells.
DNA: Deoxyribonucleic Acid. The chemical substance that codes the genetic information. Or A nucleic acid that carries the genetic information in the cell and is capable of self-replication and synthesis of RNA. DNA consists of two long chains of nucleotides twisted into a double helix and joined by hydrogen bonds between the complementary bases adenine and thymine or cytosine and guanine. The sequence of nucleotides determines individual hereditary characteristics.
DOMINANT: An allele that causes the homozygous form and the heterozygous form to look the same as each other, but different than wild type. Of, relating to, or being an allele that produces the same phenotypic effect whether inherited with a homozygous or heterozygous allele.
DUAL PHENOTYPE: Mosaicism. A condition in which tissues of genetically different types occur in the same organism.
ENZYME: A catalytic protein. The basic workhorse of life.
EPISTASIS: also EPISTATIC: When one gene blocks another gene from expressing itself. The genes could be on the same chromosome or different chromosomes; Or Epistasis is the interaction between genes. Epistasis takes place when the effects of one gene are modified by one or several other genes, which are sometimes called modifier genes. The gene whose phenotype is expressed is said to be Epistatic, while the phenotype altered or suppressed is said to be hypostatic. Epistasis should be distinguished from Dominance, which is an interaction between alleles at the same gene locus.
EXPRESS: To have an effect. A dominant gene is able to express itself while a recessive gene remains hidden if paired with a dominant gene.
EXPRESSIVITY: The amount of effect. Usually refers to less then a full expression due to co-dominant genes or modifiers.
EUCHROMOSOME: A chromosome that is not a sex chromosome or any chromosome except the gender, sex chromosome. Also called AUTOSOME.
FACTOR: also GENE: A gene. That part of a chromosome, which effects a certain characteristic. For example, the gene or factor for cob
GAMETE: A sperm cell or an egg cell. A gamete cell is created through meiosis.
GENDER CHROMOSOME: The chromosome that determines individuals gender. For pigeons, Z and W chromosomes are the common designation in general genetic literature and X and Y-chromosomes are the common designations in avicultural literature.
GENDER LINKED: Any gene found on the Z chromosome, for example the gene alleles for almond, dilute, pale, reduced, ash-red, wild type blue/black or brown.
GENE: also FACTOR: A hereditary unit consisting of a sequence of DNA that occupies a specific location on a chromosome and determines a particular characteristic in an organism. Genes undergo mutation when their DNA sequences changes. A part of a chromosome that effects a certain characteristic, for example the gene or factor for colors.
GENE POOL: All the genes in a set of birds, for example, all the pigeons in your loft.
GENETICS: (used with a sing. verb) That branch of biology which deals with heredity, especially the mechanisms of hereditary transmission and the variation of inherited characteristics among similar or related organisms.
(used with a pl. verb) A genetic constitution of an individual, a group, or a class.
That branch of biology, which studies heredity and variation in organisms.
The way characteristics are inherited.
GENOTYPE: The specific (actual) genes at an allele. see phenotype.
GERM CELL: A gamete.
HALF SIDER: Mosaicism. Dual Phenotype. The condition where more then one genetically distinct population of cells coexists within one individual. 0ne individual with two or more genetic constitutions. "The opposite of twins." A condition in which tissues of genetically different types occur in the same organism.
HAPLOID: Having the same number of sets of chromosomes as a germ cell or half as many as a somatic cell. Having a single set of chromosomes. Having single chromosomes from only one parent and NOT chromosome pairs from both parents.
HEMIZYGOUS: A hen. Having only one Z chromosome.
HERITABLE: Can inherit or be inherited; or Capable of being passed from one generation to the next; hereditary. Capable of inheriting or taking by inheritance
HETEROZYGOUS HETEROZYGOUS: or HETEROZYGOTE: Mixed zygote. Having different alleles at a specific locus; or Having different alleles at one or more corresponding chromosomal loci. Of or relating to a heterozygote. Also see Homozygote.
HOMOLOGOUS CHROMOSOME: A Chromosome Pair, one from the female parent and the other from the male having the same morphology and linear sequence of gene loci.
HOMOLOGOUS PAIR: A set of Homologous Chromosomes; or A pair of chromosomes having the same morphology and linear sequence of gene loci.
HOMOZYGOTE: or HOMOZYGOUS: An organism that has the same alleles at a particular gene locus on homologous chromosomes; or Pure for any given genetic trait.
HYBRID: A Mule. The offspring of genetically dissimilar parents or stock, especially the offspring produced by breeding plants or animals of different varieties, species, or races.
HYPOSTASIS: A condition in which the action of one gene conceals or suppresses the action of another gene that is not its allele but that affects the same part or biochemical process in an organism. See also Epistasis for blocking hypostatsis phenotypes.
INBREEDING: or INBREED: Crossing an individual with a close family member; or To breed by the continued mating of closely related individuals, especially to preserve desirable traits in a stock.; or To breed or develop within; engender. This is often the best way to discover recessive genes within a family.
INCOMPLETE DOMINANCE: or CO DOMINANCE, which is the preferred term. - an allele that causes the homozygous form to look different than wild type and the heterozygous form to have traits of both. (All three look different from each other.) A condition in which both alleles of a gene pair in a heterozygote are fully expressed, with neither one being dominant or recessive to the other.
INDEPENDENT ASSORTMENT: Occurs during meiosis in the creation of gamete cells. Each of the chromosomes in the chromosome Pairs separate from each other and independently move to different halves of the cell division. It's one of the processes that make each gamete cell unique.
INHERIT: To receive (a characteristic) from one's parents by genetic transmission.
INHERITANCE: The action of inheriting; Any characteristic passed on; The process of genetic transmission of characteristics from parents to offspring; or A characteristic so inherited; Or The sum of characteristics genetically transmitted from parents to offspring.
LINKAGE: or LINKED: Genes that are members of the same chromosome; or An association between two or more genes such that the traits they control tend to be inherited together.
LOCUS: A location on a chromosome or chromosome pair; A specific place that defines an allele; or The position that a given gene or its allele occupies on a chromosome.
MEIOSIS: The creation of unique cells through the process of crossover and independent assortment; The type of cell division that occurs during gamete creation; The process of cell division in sexually reproducing organisms that reduces the number of chromosomes in reproductive cells from diploid to haploid, leading to the production of gametes in animals and spores in plants; or The process that results in the formation of egg and or sperm cells.
MENDEL'S LAWS: Gregor Mendel began his first genetics experiment in 1856 and published his work in 1866. It went unnoticed until about 1900. His work is recognized for establishing two basic principles. The Law of Segregation and The Law of Independent Assortment.
MICRO CHROMOSOME: A chromosome that is to small to positively identify as a chromosome. There are 40 pairs of known chromosomes in pigeons, in addition there are many which are to small to identify. Therefore the exact number of chromosomes in a pigeon is unknown.
MITOSIS: Normal cell division; Not meiosis; or The process in cell division by which the nucleus divides, typically consisting of four stages, prophase, metaphase, anaphase, and telophase, and normally resulting in two new nuclei, each of which contains a complete copy of the parental chromosomes; Also called KARYOKINESIS. The entire process of cell division including division of the nucleus and the cytoplasm.
MODIFIER: Secondary genes that modify the expressivity of a co-dominant or dominant gene.
MOSAICISM: The condition where more then one genetically distinct population of cells coexists within one individual. 0ne individual with two or more genetic constitutions. "The opposite of twins." A condition in which tissues of genetically different types occur in the same organism.
MULTIPLE ALLELE: A multiple gene effect. A characteristic with a range of expressivity brought about by modifiers; or A series of genes that occupy a specific position (locus ) on a specific chromosome.
MUTANT: or MUTATION: An individual, organism, or new genetic character arising or resulting from mutation; or A changed gene or an individual carrying a changed gene.
PENETRANCE: The frequency, under given environmental conditions, with which those individuals with a specific genotype express a specific phenotype; or The percentage of individuals that, carrying a gene, actually express that genes phenotype.
PHENOTYPE: The observable physical or biochemical characteristics of an organism, as determined by both genetic makeup and environmental influences; or The expression of a specific trait, such as stature or blood type, based on genetic and environmental influences; or An individual or group of organisms exhibiting a particular phenotype. The appearance. What the dominant genes express. see genotype.
PLURAL CHIASMATA: The point of contact between paired chromatids during meiosis, resulting in a cross-shaped configuration and representing the cytological manifestation of crossing over; Or Chiasma. A connection between a pair of homologous chromosomes which occurs during meiosis; or The prelude to crossing over; or The first stage in mitosis;
PUNNETT SQUARE: A chart to project potential results of a mating? This chart or square as it is called was developed by Reginald Punnet a professor at Cambridge University in the early 1900s.
RECESSIVE: Of, relating to, or designating an allele that does not produce a characteristic effect when present with a dominant allele; or Of or relating to a trait that is expressed only when the determining allele is present in the homozygous condition; or A gene that is not visible when paired with other genes. The least expressive gene at the allele of a chromosome pair. The opposite of dominant.
RECOMBINATION: The natural formations in offspring of genetic combinations not present in parents, by the processes of crossing over or independent assortment; or the appearance in offspring of new combinations of allelic genes from the mixing of chromosomes and their parts.
SEGREGATION: The separation of paired alleles or homologous chromosomes, especially during meiosis, so that the members of each pair appear in different gametes; or the separation of alleles during meiosis so that each gamete contains only one of the two alleles. Every individual carries two alleles, one from each of its parents. i.e. The parent only passes one allele of its two possibilities.
SEX CHROMOSOME: see also GENDER CHROMOSOME: The chromosome that determines an individuals gender. In pigeons this is the W and Z chromosomes. In mammals it would be the X and Y chromosomes.
SEX LINKED: see also GENDER LINKED: Any gene on the Z chromosome. For example the pigment color gene.
TEST CROSS: Pairing an individual having unknown genes with one known to be a homozygous recessive. This allows the genes of the unknown individual to eventually express themselves through their offspring. The best cross test is with a brown barless which is the most recessive genotype / phenotype.
WILD TYPE: or WILD GENE: The gene or genotype that represents the typical specimen found in nature. usually represented with the symbol +.
ZYGOTE: The fertilized diploid egg cell; The first cell of a new individual; The cell formed by the union of two gametes, especially a fertilized ovum before cleavage; The organism that develops from a zygote.
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