D3.2.8 Single-nucleotide polymorphisms and multiple alleles in gene pools Notes

Gene Pools Are the Total Collection of Alleles in a Population

1. Consider for a moment that a gene pool as a vast library containing all the genetic information of a population.
2. Each individual in this population is like a book, carrying a unique combination of alleles, different versions of a gene.

Multiple Alleles in Gene Pools

1. While an individual can inherit only two alleles for a gene (one from each parent), a population can have many more alleles for the same gene.
2. This diversity is crucial for evolution and adaptation.

Apples Use Multiple Alleles to Avoid Inbreeding

1. The S-gene in apple trees prevents self-pollination, ensuring genetic diversity.
   1. There are over 30 alleles of the S-gene in the apple gene pool.
   2. Each tree inherits two alleles and rejects pollen carrying the same S-allele as its own.

Example Cross

1. A Jazz apple (S₂S₃) will reject pollen from another Jazz tree or a Golden Delicious (S₂S₃) because they share S-alleles.
2. A Gala apple (S₅S₉) can successfully cross-pollinate with Jazz or Golden Delicious because its alleles are different.

The Role of SNPs and Multiple Alleles in Evolution

1. Genetic variation, driven by SNPs and multiple alleles, is the foundation of evolution.
2. It allows populations to adapt to changing environments and resist diseases.

How Variation Drives Evolution

1. Natural Selection: Alleles that provide an advantage (e.g., resistance to a disease) become more common over generations.
2. Genetic Drift: Random changes in allele frequencies can introduce new traits.
3. Gene Flow: Migration introduces new alleles into a population, increasing diversity.

Applications of SNPs and Multiple Alleles

1. Medicine

1. SNPs help identify genetic predispositions to diseases like cancer and diabetes.
2. They also guide personalized medicine, tailoring treatments to an individual's genetic makeup.

2. Agriculture

1. Understanding multiple alleles in crops (e.g., disease resistance genes) improves breeding strategies for higher yields and resilience.

3. Conservation Biology

1. Genetic diversity, measured by SNPs and alleles, informs strategies to protect endangered species from inbreeding and extinction.