Molecular Genetics Tools for Biotechnology in Animal and Plant Breeding

Gene

A stretch of DNA that influences a trait, often by coding for a protein or regulating gene expression.

Allele

A version of a gene (for example, one that produces pigment vs one that doesn’t).

Genotype

The allele combination an individual carries for a gene (for example, $AA$, $Aa$, or $aa$).

Phenotype

The observable trait which results from genotype and can be influenced by environment.

Homozygous

Having two of the same allele (for example, $AA$ or $aa$).

Heterozygous

Having two different alleles (for example, $Aa$).

Dominant allele

Shows its effect in the phenotype even when only one copy is present.

Recessive allele

Typically shows in the phenotype only when two copies are present.

Punnett square

A structured way to predict how alleles from two parents can combine in offspring.

Mendel’s Law of Segregation

During gamete formation, the two alleles for a gene separate so each gamete gets only one.

Mendel’s Law of Independent Assortment

Alleles for different genes assort into gametes independently if the genes are not linked.

Artificial selection

When humans choose which individuals reproduce to increase desired traits in the next generation.

Qualitative trait

A trait with distinct categories; often controlled by one or a few genes.

Quantitative trait

A trait showing continuous variation, typically influenced by many genes and environment.

DNA replication

The process of making an accurate copy of DNA before cell division.

Transcription

The process of using a DNA sequence as a template to build an RNA molecule.

Translation

The process of reading mRNA to build a protein chain at the ribosome.

Codon

A group of three nucleotides in mRNA that corresponds to an amino acid.

Mendelian inheritance

Patterns of inheritance that are predictable based on Mendel's laws.

Marker-assisted selection

Selecting animals/plants using DNA markers linked to traits.

Heterosis

Hybrid vigor, where crossbred offspring outperform the average of the parents.

Mutations

Changes in DNA that can affect traits and might be harmful, neutral, or beneficial.

Environmental influence

The impact of external factors on an organism's traits, especially noteworthy in quantitative traits.

Inbreeding depression

Reduced fitness and increased incidence of recessive disorders due to breeding too narrowly.

Gametes

Reproductive cells that carry one allele for each gene.

Carrier

An individual with a recessive allele that does not show in the phenotype.

Phenotype ratio

The relative frequency of different phenotypes in the offspring.