6.3 Mendel and Heredity

Mendel laid the groundwork for genetics. Gregor Mendel Austrian monk 1800s Mathematician Most famous for correctly predicting the results of meiosis before the discovery of chromosomes. He recognized that traits are inherited as discrete units (genes) from parental generation. He was the first to describe how traits are passed.

Mendel laid the groundwork for genetics. The study of biological inheritance patterns and variations in organisms. Traits – distinguishing characteristics that are inherited ex. eye color, leaf shape, tail length hereditary – passed from one generation to the next

Mendel’s data revealed patterns of inheritance. Read about Mendel’s experiment p 177 – 179 Experimental Design Purebred – type of organism whose ancestors are genetically uniform Results Cross – the mating of two organisms Conclusions Law of segregation – Mendel’s First Law Organisms inherit two copies of each gene, one from each parent. Organisms donate only one copy of each gene in their gametes. Thus, the two copies of each gene segregate during gamete formation.

6.4 Traits, Genes, and Alleles

The same gene can have many versions. gene – a piece of DNA that provides a set of instructions to a cell to make a certain protein Each gene has a locus (specific location on a pair of homologous chromosomes). Allele – any of the alternative forms of a gene that may occur Each gene has two alleles, one from each parent. Homozygous – two of the same alleles at a specific locus Heterozygous – two different alleles at a specific locus

Genes influence the development of traits. Genome – all of an organism’s genetic material Genotype – the genetic makeup of a specific set of genes Phenotype – the physical characteristics, or traits Dominate allele – the allele that is expressed when two different alleles or two dominate alleles are present Recessive allele - the allele that is only expressed when two copies are present