Biol 104 Lec 09 Mendelian Genetics - Patterns of...

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Patterns of Inheritance Dogs 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 makeup Sequencing 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 mathematics 2. 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 finding was not understood by the scientific community until the early 1900s . Hugo de Vries and Carl Correns felt they had clarified the concept of heredity for their research. They came to find out a Austrian Monk had already come to the same conclusions in publication that had received no attention from the scientific community 50 years earlier .
chromosome 1 from tomato pair of homologous chromosomes Mendel was still able to clarify the concept of heredity even though he did not have an understanding of important facts we know today 1. Genes are carried at specific locations on chromosomes called loci 2. A given gene can come in several alternative forms: alleles e.g., A, B, O blood groups Mendel knew the allele as a “ heritable factor
3. Adults have two copies of each gene carried in homologous chromosomes a) Homozygou s: both copies identical b) 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 1 from tomato pair of homologous chromosomes Some important concepts that Mendel did not know (cont.):
Experimental genetics began in an abbey garden Gregor Mendel discovered principles of genetics in experiments with the pea plants Mendel showed that parents pass heritable factors to 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 success 1)

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