This is a comprehensive glossary of terminology related to Animal Genetics, organized alphabetically from A to Z. Each term is briefly defined in the context of animal genetics, ensuring coverage of key concepts without missing relevant terms. Given the breadth of the field, this glossary includes foundational, technical, and applied terms used in animal genetics, genomics, and breeding.
A
- Additive Genetic Effect: The cumulative effect of individual genes on a trait, where the contribution of each allele is summed without interaction.
- Allele: One of the alternative forms of a gene at a specific locus on a chromosome.
- Allele Frequency: The proportion of a specific allele in a population’s gene pool.
- Amplification (DNA): The process of increasing the number of copies of a specific DNA segment, often used in PCR (Polymerase Chain Reaction).
- Anaphase: The stage of cell division (mitosis) where sister chromatids are pulled apart to opposite poles of the cell.
- Aneuploidy: An abnormal number of chromosomes in a cell, often leading to genetic disorders.
- Artificial Insemination (AI): A breeding technique where semen is collected and manually introduced into a female’s reproductive tract.
- Assortative Mating: Non-random mating where individuals choose partners based on similar (positive) or dissimilar (negative) traits.
- Autosome: A chromosome that is not a sex chromosome, carrying genes for non-sex-related traits.
B
- Backcrossing: A breeding method where a hybrid is crossed with one of its parents or a genetically similar individual to reinforce desired traits.
- Base Pair (bp): The unit of DNA consisting of two complementary nucleotides (e.g., A-T, C-G) held together by hydrogen bonds.
- Biotechnology: The use of living organisms or their components to develop products, including genetic engineering in animals.
- Bottleneck Effect: A reduction in genetic diversity due to a drastic decrease in population size.
- Breed: A group of animals within a species that share specific physical or genetic characteristics due to selective breeding.
- Breeding Value: The genetic merit of an individual for a specific trait, used in selection programs.
C
- Candidate Gene: A gene suspected to influence a specific trait based on its function or location.
- Centimorgan (cM): A unit of genetic linkage, representing a 1% chance of recombination between two loci during meiosis.
- Chromosome: A structure in the cell nucleus that carries DNA, organized into genes.
- Cisgenic: An organism modified with genes from the same or a closely related species.
- Cloning: The process of creating a genetically identical copy of an organism or gene.
- Codominance: A genetic situation where both alleles in a heterozygote are fully expressed (e.g., AB blood type).
- Coefficient of Inbreeding: A measure of the probability that two alleles at a locus are identical by descent.
- Crossbreeding: Mating individuals from different breeds or populations to combine desirable traits.
- Cytogenetics: The study of chromosome structure, function, and abnormalities in relation to genetics.
D
- Deoxyribonucleic Acid (DNA): The molecule that encodes genetic information in all living organisms.
- Dihybrid Cross: A genetic cross involving two traits, each controlled by a different gene.
- Diploid: A cell or organism with two sets of chromosomes (2n), one from each parent.
- Dominance: A genetic relationship where one allele masks the expression of another in a heterozygote.
- Drift (Genetic): Random changes in allele frequencies in a population, especially in small populations.
- Duplication: A type of mutation where a segment of DNA is copied, leading to extra genetic material.
E
- Embryo Transfer (ET): A reproductive technology where embryos are collected from a donor and transferred to a recipient female.
- Epigenetics: The study of heritable changes in gene expression that do not involve changes to the DNA sequence.
- Epistasis: The interaction between genes where one gene’s expression affects or masks another gene’s effect.
- Estimated Breeding Value (EBV): A statistical prediction of an animal’s genetic merit for a trait based on performance data.
- Exon: The coding region of a gene that is expressed in the final mRNA product.
F
- F1 Generation: The first filial generation, resulting from a cross between two genetically distinct parents.
- F2 Generation: The second filial generation, produced by crossing F1 individuals.
- Fitness: The ability of an organism to survive and reproduce, influenced by its genetic makeup.
- Fixation: When an allele becomes the only variant at a locus in a population due to selection or drift.
- Founder Effect: Reduced genetic diversity in a population established by a small number of individuals.
- Frameshift Mutation: A mutation caused by the insertion or deletion of nucleotides that shifts the reading frame of a gene.
G
- Gamete: A reproductive cell (sperm or egg) carrying half the genetic material of an organism.
- Gene: A segment of DNA that encodes a functional product, such as a protein or RNA.
- Gene Editing: Precise modification of DNA using tools like CRISPR/Cas9 to alter specific genes.
- Gene Flow: The transfer of genetic material between populations through migration or mating.
- Gene Pool: The total collection of genes and alleles in a population.
- Genetic Correlation: The degree to which two traits are influenced by the same genes.
- Genetic Distance: A measure of the genetic divergence between populations or individuals.
- Genetic Engineering: Direct manipulation of an organism’s genes using biotechnology.
- Genetic Linkage: The tendency of genes on the same chromosome to be inherited together.
- Genetic Map: A diagram showing the relative positions of genes on a chromosome based on recombination frequencies.
- Genetic Marker: A specific DNA sequence used to identify individuals or track inheritance of traits.
- Genetic Variation: The diversity of alleles and genotypes within a population.
- Genome: The complete set of DNA in an organism, including all its genes.
- Genomics: The study of the structure, function, and evolution of genomes.
- Genotype: The genetic makeup of an organism, typically referring to specific alleles at a locus.
- Genotyping: The process of determining an individual’s genetic makeup at specific loci.
H
- Haploid: A cell or organism with a single set of chromosomes (n), typically gametes.
- Haplotype: A set of alleles at multiple loci inherited together on the same chromosome.
- Hardy-Weinberg Equilibrium: A theoretical state where allele and genotype frequencies remain constant across generations in the absence of evolutionary forces.
- Heritability: The proportion of phenotypic variation in a population attributable to genetic variation.
- Heterosis (Hybrid Vigor): The enhanced performance of hybrids compared to their parents, often due to increased genetic diversity.
- Heterozygote: An individual with two different alleles at a specific locus.
- Homozygote: An individual with two identical alleles at a specific locus.
I
- Inbreeding: Mating between closely related individuals, increasing homozygosity and potentially harmful recessive traits.
- Inbreeding Depression: Reduced fitness or performance due to increased homozygosity from inbreeding.
- Independent Assortment: The random distribution of alleles from different genes into gametes during meiosis, as described by Mendel.
- Insertion: A mutation where extra nucleotides are added to a DNA sequence.
- Introgression: The transfer of genetic material from one species or population into another through repeated backcrossing.
- Intron: A non-coding region of a gene that is removed during RNA splicing.
J
- Junk DNA: Non-coding DNA segments that may not have a known function, though some may play regulatory roles.
K
- Karyotype: The number and visual appearance of chromosomes in a cell, used to detect abnormalities.
- Knockout: A genetic modification that inactivates a specific gene to study its function.
L
- Lethal Allele: An allele that causes death, often in homozygous form.
- Linkage Disequilibrium (LD): Non-random association of alleles at different loci, often due to physical proximity on a chromosome.
- Locus (pl. Loci): The specific position of a gene or DNA sequence on a chromosome.
M
- Marker-Assisted Selection (MAS): A breeding strategy that uses genetic markers to select for desired traits.
- Meiosis: The process of cell division that produces gametes with half the chromosome number of the parent cell.
- Mendelian Inheritance: The pattern of inheritance for traits controlled by single genes, following Mendel’s laws.
- Microsatellite: Short, repetitive DNA sequences used as genetic markers due to high variability.
- Mitochondrial DNA (mtDNA): DNA located in mitochondria, inherited maternally and used in population genetics studies.
- Mitosis: The process of cell division that produces two identical daughter cells.
- Monohybrid Cross: A genetic cross involving one trait controlled by a single gene.
- Mutation: A change in the DNA sequence, which may be beneficial, neutral, or harmful.
N
- Natural Selection: The process by which traits that confer a survival or reproductive advantage become more common in a population.
- Non-disjunction: The failure of chromosomes to separate properly during meiosis, leading to aneuploidy.
- Nucleotide: The basic building block of DNA, consisting of a sugar, phosphate, and base (A, T, C, or G).
- Nucleus: The cell organelle containing most of an organism’s genetic material.
O
- Outbreeding: Mating between unrelated or distantly related individuals to increase genetic diversity.
- Overdominance: A situation where heterozygotes have higher fitness than either homozygote.
P
- Pedigree: A diagram showing the genetic relationships and inheritance patterns within a family or population.
- Phenotype: The observable traits of an organism, resulting from the interaction of its genotype and environment.
- Pleiotropy: When a single gene affects multiple traits.
- Polygenic Trait: A trait influenced by multiple genes, often showing continuous variation (e.g., height, milk yield).
- Polymerase Chain Reaction (PCR): A technique to amplify specific DNA segments for analysis.
- Polymorphism: The occurrence of two or more variants (alleles, phenotypes) in a population.
- Population Genetics: The study of allele and genotype frequency changes in populations over time.
- Progeny Testing: Evaluating the genetic merit of an individual based on the performance of its offspring.
- Promoter: A DNA region that initiates transcription of a gene.
Q
- Quantitative Genetics: The study of traits influenced by multiple genes and environmental factors, often using statistical methods.
- Quantitative Trait Locus (QTL): A genomic region associated with variation in a quantitative trait.
R
- Recombination: The exchange of genetic material between homologous chromosomes during meiosis, creating new allele combinations.
- Recessive Allele: An allele whose effect is masked by a dominant allele in a heterozygote.
- Restriction Enzyme: A protein that cuts DNA at specific sequences, used in genetic analysis.
- RNA (Ribonucleic Acid): A molecule that translates DNA into proteins or performs other functions in gene expression.
S
- Selection: The process of choosing individuals with desirable traits to reproduce, altering allele frequencies.
- Selection Differential: The difference between the mean of selected individuals and the population mean for a trait.
- Sex Chromosome: Chromosomes (e.g., X, Y) that determine the sex of an organism.
- Sex-Linked Trait: A trait controlled by genes on sex chromosomes, often showing different inheritance patterns in males and females.
- Single Nucleotide Polymorphism (SNP): A variation at a single nucleotide position in the genome, used as a genetic marker.
- Somatic Cell: Any cell in the body except gametes, not involved in inheritance.
- Splicing: The process of removing introns and joining exons in mRNA during gene expression.
T
- Telomere: The protective end of a chromosome, preventing degradation or fusion.
- Trait: A specific characteristic or feature of an organism, such as coat color or milk production.
- Transcription: The process of copying DNA into RNA as the fint step in gene expression.
- Transgene: A gene introduced into an organism from another species or synthesized artificially.
- Transgenic: An organism containing foreign DNA introduced through genetic engineering.
- Translation: The process of synthesizing a protein from mRNA.
- Translocation: A chromosomal abnormality where a segment of one chromosome is transferred to another.
U
- Uniparental Inheritance: Inheritance of genetic material from only one parent, such as mitochondrial DNA from the mother.
V
- Variance (Genetic): The measure of genetic diversity within a population for a specific trait.
- Viability: The ability of an organism to survive to reproductive age, often influenced by genetics.
W
- Wild Type: The standard or most common phenotype or genotype in a natural population.
X
- X Chromosome: A sex chromosome, typically present as XX in females and XY in males in mammals.
- X-Linked: Genes or traits carried on the X chromosome, often affecting males more severely due to hemizygosity.
Y
- Y Chromosome: A sex chromosome, typically present in males (XY), carrying genes related to male sex determination.
- Y-Linked: Genes or traits carried on the Y chromosome, inherited only by males.
Z
- Zygote: The fertilized egg formed by the fusion of sperm and egg, containing a diploid set of chromosomes.
