Genetics of dairy production

Lesson

Genetics of dairy production
- Introduction
- Learning objectives
- Review of Mendelian genetics
  - Introduction
  - Essential vocabulary about genetics
  - Relation between the phenotype and the genotype
  - Expected results for more than one trait
  - Conclusion
- Principle of genetic selection in dairy cattle
- Conclusion

Essential vocabulary about genetics

The genetic material is contained on chromosomes which are found in the nucleus of each cell. These chromosomes are paired and cows have 30 pairs of chromosomes.

From this example of an homologous pair of chromosomes, we can define four terms:

A gene is a section of DNA that determines a trait.
Since chromosomes are paired, genes are also paired.
Therefore, these genes can have different forms which are called alleles.
When the two alleles of a gene are the same (here AA), then the cow is said to be homozygous for the trait coded by the orange traits. However, when the two alleles are different (here Bb), the cow is said to be heterozygous for this trait.

The gene combination of an organism defines the genotype of this organism. Half of these genes will be transfered to the offspring.

However, most of the time, we don't know exactly the gene combination of an organism. What we know is its phenotype, which is the way this organism looks. In dairy cows, we are particularly interested in the phenotype of traits that can be recorded such as the quantity of milk produced by a cow.

Now that we have defined the genotype and the phenotype, a new question arises:

How is the phenotype related to the genotype?

Homepage