Fundamentals of Genetics CHAPTER 9

Patterns of Inheritance The History of Genetics Genetics – scientific study of heredity Trait – characteristic that can be passed from parents to offspring

Father of Genetics Gregor Mendel (born 1822) Austrian Monk Studied 7 different pea plant traits that are true-breeding Produce offspring identical to themselves https://www.youtube.com/watch?v=GTiOETaZg4w

Parental Cross Cross-pollinated flowers with opposite traits (tall, short) P generation Plants from the first cross were all tall- hybrids. F1 generation

F1 Cross Allowed f1 plants to self-fertilize The recessive trait had reappeared!! About 25% of the offspring (F2 generation) were short.

Mendel’s Conclusions https://www.youtube.com/watch?v=Mehz7tCxjSE 1. Biological inheritance is passed from one generation to the next- Genes Alleles- different forms of a gene 2. Some alleles are dominant Capital Letter -R,D Some alleles are recessive Lowercase letters – r, d 3. Principle of Segregation Alleles separate from each other during formation of sex cells, or gametes. https://www.youtube.com/watch?v=Mehz7tCxjSE

Genes Represent Traits Genotype – genes that make up an organism Includes both genes in a homologous pair Phenotype – outward expression of the trait Homozygous – two alleles are identical (AA or aa) Heterozygous – two alleles are different (Aa) Also known as a hybrid organism Purebred – organism receives the same genetic traits form both of its parents Homozygous – AA or aa Hybrid – organism receives different forms of a genetic trait Heterozygous - Aa

Important Terms Genes – sections of a chromosome that code for a trait Allele – distinct form of a gene Dominant Allele – expressed when two different alleles are present; represented with capital letter Recessive Allele – form of gene that is not expressed when paired with a dominant allele; represented with lower case letter

Genetics and Prediction

Predictions for One Trait Probability – predict likelihood of an event or outcome Punnett square – grid for organizing genetic information Can be used to make predictions about a cross between two organsims Monohybrid Cross – cross between two parents and one trait

Monohybrid Cross

Predictions for Two Traits Dihybrid Cross – cross between two parents and two traits Use a 4 x 4 Punnett square Sixteen possible outcomes

Incomplete Dominance Heterozygous offspring show a phenotype that is in-between the phenotypes of the two homozygous parents Blending of traits Color in snapdragons; instead of white or red, color is pink

Codominance Both alleles are expressed Example: Blood type IA, IB, i(O), or IAIB blood type Both A and B are dominant so they are both expressed in the IAIB blood type

Polygenic Trait Trait controlled by more than one gene Example: eye color https://www.youtube.com/watch?v=CBezq1fFUEA