Beef Cattle Genetics Terms

 

A Glossary of Beef Cattle Genetics Terms

   Adenine:
     One of the four bases in DNA that make up the letters ATGC, adenine is the "A". The others are guanine, cytosine, and thymine. Adenine always pairs with thymine.

Allele:
     The various possible forms of a gene. A single allele for each locus (location on a chromosome) is inherited from each parent. Different alleles produce variation in inherited characteristics such as coat color. In an individual, one form of the allele (the dominant one) may be expressed more than another form (the recessive one). When an individual has two identical alleles for the same trait, (AA, bb, etc.), they are homozygous. Two contrasting alleles of the same trait (Aa, Bb, etc.) are heterozygous.

Base Pair:
     Two bases which form a "rung of the DNA ladder." A DNA nucleotide is made of a molecule of sugar, a molecule of phosphoric acid, and a molecule called a base. The bases are the "letters" that spell out the genetic code. In DNA, the code letters are A, T, G, and C, which stand for the chemicals adenine, thymine, guanine, and cytosine, respectively. In base pairing, adenine always pairs with thymine, and guanine always pairs with cytosine.

Cell:
     The basic unit of any living organism. It is a small, watery, compartment filled with chemicals and a complete copy of the organism's genome.

Chromosome:
     The structure in the cell nucleus that stores and transmits genetic information in the form of DNA. Each parent contributes one chromosome to each pair, so offspring get half of their chromosomes from their dam and half from their sires.

Cytosine:
     One of the four bases in DNA that make up the letters ATGC, cytosine is the "C".

The others are adenine, guanine, and thymine. Cytosine always pairs with guanine

DNA

     (Deoxyribonucleic Acid) The chemical inside the nucleus of a cell that carries the genetic instructions for making living organisms. It is the molecule that encodes genetic information.

DNA replication:

     The process by which the DNA double helix unwinds and makes an exact copy of itself.

Dominant:
     A gene that almost always results in a specific physical characteristic. Only one copy the gene is needed in order for the trait to appear.

Double Helix:
     The structural arrangement of DNA, which looks something like an immensely long

ladder twisted into a helix, or coil.

Environment:
      Factors that influence the expression of genes such as nutrition, disease, weather, management, etc.

Gene:
     The functional and physical unit of heredity passed from parent to offspring.

Genotype:
     The genetic identity of an individual as distinguished from its physical appearance

(phenotype).

Gene Mapping:
     Determining the relative positions of genes on a chromosome and the distance between them.

Genetic Marker:
     Known sequence believed to be near actual genes and statistically associated with phenotype. Markers are used to find genes, but can be used in some cases for selection before the gene is known. The closer the marker is to the gene, the more consistent the effect.

Genome:
     All the genetic material in the chromosomes of a particular organism.

Genotype:
     The genetic identity of an individual that does not show as outward characteristics.

Guanine:
     One of the four bases in DNA that make up the letters ATGC, guanine is the "G". The others are adenine, cytosine, and thymine. Guanine always pairs with cytosine.

Heterozygous: Possessing two different forms of a particular gene, one inherited from each parent.

Homozygous:
     Possessing two identical forms of a particular gene, one inherited from each parent.

Locus: The place on a chromosome where a specific gene is located, a kind of address for the gene.

Mendelian Inheritance:
     Manner in which genes and traits are passed from parents to offspring.

Microsatellite:
     Repetitive stretches of short sequences of DNA used as genetic markers to track inheritance in families.

Natural Variation:
      A permanent structural alteration in DNA. In most cases, DNA changes either have no effect or cause harm, but occasionally a mutation can improve an organism's chance of surviving and passing the beneficial change on to its descendants.

Nucleus:
     The central cell structure that houses the chromosomes.

Nucleotides:
     One of the structural components, or building blocks, of DNA. A nucleotide consists of a base (one of four chemicals: adenine, thymine, guanine, and cytosine) plus a molecule of sugar and one of phosphoric acid.

Phenotype:
     The observable traits or characteristics of an organism, for example hair color, weight, or the presence or absence of a disease. Phenotypic traits are not necessarily genetic and results from the interaction of genotype and the environment.

Quantitative Trait Loci (QTL):
     The location on the chromosome that contains a gene or genes affecting economically important quantitative traits.

Recessive: A trait that appears only in animals who have received two copies of a non-dominate gene, one from each parent.

Single Nucleotide Polymorphisms (SNPs):
     Pronounced “snip” This is a functional variation that occurs at a specific point in the DNA – on one of the rungs of the DNA ladder called nucleotides. It is predictable, and its occurrence in the population cannot be attributed to recurrent random variation alone. Thus, it is called a Stable Variant Allele.

Thymine:
     One of the four bases in DNA that make up the letters ATGC, thymine is the "T". The others are adenine, guanine, and cytosine. Thymine always pairs with adenine.

For more information on related terms please visit  the Talking Glossary of Genetic Terms   website.