Every beef animal has approximately 30 billion base pairs of genes, with approximately 100 million base pairs packed into 30 boxes known as chromosomes.
DNA is important, not only at conception but throughout the animals life. DNA provides the software for each cells hardware. In essence, depending on the cells function, parts of the DNA are turned on, or expressed, and tell the cells how to behave.
The DNA of each beef animal is created at conception. DNA has base pairs of genes, which forms the “ladder” of a DNA strand (the sires side and the dams side). However, sperm and ovum only have one side of the ladder each, the full ladder is fully formed when the two come together at conception.
As to which genes are present in each sperm or ovum, there is a random shuffling that occurs. In the case of sperm, as each one is created, nature selects the chromosomes to make the sperm from either side of the donor sires DNA ladder. Given there are only 30 different chromosomes, it is natural to assume that there are only limited choices, however it’s the same as tossing a coin as to which chromosome is selected. If you toss a coin 30 times, there are over a billion different combinations.
That just accounts for the sperm, there is also the same in ovum and then there can be reshuffling within the chromosomes. All this means that at a genetic level, every individual is unique and the uniqueness of each animal is a random process.
We know that is true, most siblings in a family will recognise their differences. On average full siblings will only share 50% of their genetics. In reality though, the percentage can be higher or lower.
So why does genetic evaluation exist? It is trying to describe the genetic differences in individuals created by this random shuffling.