Biology Ch. 12: Mendel and Heredity “What are the chances?”

12.1 Origins of Hereditary Science Results of breeding crops and livestock is some of the first recorded information Heredity  the study of the passing of traits from generation to generation. Genetics  the study of genes and genetic information.

Gregor Mendel: The Father of Modern Genetics Austrian monk 1800’s University of Vienna; math and biology Statistics Pea plants

“Cross”, pollinate, self-pollinating Contrasting traits, “characters”….a trait is one of the possible forms…allele (form) Hybrids Monohybrid crosses Generation

Mendel’s First Experiments Cross purple flower with purple flower; all offspring have purple flowers Cross white flower with white flower; all offspring have white Cross purple flower with white; all purple – the purple allele seems to be the ‘dominant’ trait.

Punnett Square Vocabulary Trait/character = genetic traits; something like height, color,etc Allele = forms/versions that genes can be expressed in; color can be green or yellow Dominant allele = form that is always expressed; both GG and Gg are green peas Recessive allele = this form recedes (hides) into the background, only expressed if it’s the only choice; only gg is yellow pea (‘not green’ or yellow)

Vocab. continued Monohybrid cross = only looking at one trait with contrasting alleles Each parent gives each offspring one gene, offspring then contain pairs of genes (meiosis) Punnett square shows statistical chances of inheriting certain traits. Genotype – what genes are inherited Genotypic ratio – number of offspring inheriting that gene combination Phenotype – what is physically expressed as a result of the alleles inherited Phenotypic ratio – number of offspring that express each characteristic

Mom; Gg; gives either G or g Dad; Gg; gives either G or g Genotypic ratio 1GG: 2Gg: 1gg Phenotypic ratio 3 green: 1 not green (yellow) Zygote = fertilized egg with pairs of chromosomes Homozygous = cell has same information from mom and dad (DD or dd) Heterozygous= cell has different information from mom and dad (Dd) Cross a heterozygous green pod pea with a heterozygous green pod pea (Gg x Gg)