Patterns of InheritanceDogs are one of man’s longest genetics experiments•Dog breeds are the result of artificial selection •Populations of dogs became isolated from each other •Humans chose dogs with specific traits for breeding•Each breed has physical and behavioral traits due to a unique genetic makeupSequencing of the dog’s genome shows evolutionary relationships between breeds
The science of genetics has ancient roots•Pangenesis was an early explanation for inheritance–It was proposed by Hippocrates about 2,000 years ago–Particles called pangenes came from all parts of the organism to be incorporated into eggs or sperm –Characteristics acquired during the parents’ lifetime could be transferred to the offspring•It was not until the mid 1800’s from the work of Gregory Mendel did the fundamentals principles of genetic become clear
How did Gregor Mendel lay the foundation for modern genetics?1.Mendel from his education at the University of Vienna had a good understanding of botany and mathematics2.From his studies with breeding of pea plants at the St. Thomas monastery, his experiments demonstrated inheritance of discrete heritable factors (today known as genes)
How did Gregor Mendel lay the foundation for modern genetics?The importance of Mendel’s findingwas not understood by the scientific community until the early 1900s. Hugo de Vriesand Carl Corrensfelt they had clarified the concept of heredity for their research.They came to find out a Austrian Monkhad already come to the same conclusions in publication that had received no attention from the scientific community 50 years earlier.
chromosome 1from tomatopair of homologouschromosomesMendel was still able to clarify the concept of heredity even though he did not have an understanding of important facts we know today1. Genes are carried at specific locations on chromosomes called loci2. A given gene can come in several alternative forms: allelese.g., A, B, O blood groupsMendel knew the alleleas a “heritable factor”
3. Adults have two copies of each gene carried in homologous chromosomesa)Homozygous: both copies identicalb)Heterozygous (hybrid): two copies are different •Each homologous chromosome carries the same set of genes at the same relative position, on its chromosome.4.Differences in nucleotide sequences at a locus produce different alleles of the gene. chromosome 1from tomatopair of homologouschromosomesSome important concepts that Mendel did not know (cont.):
Experimental genetics began in an abbey gardenGregor Mendel discovered principles of genetics in experiments with the pea plants•Mendel showed that parents pass heritable factorsto offspring (heritable factors are now called genes)•Advantages of using pea plants–Controlled mating –Self-fertilization –Observable characteristics with two distinct forms–True-breeding strains
•Doing it right: The secrets of Mendel’s success1)