Introduction

Heredity Gregor Mendel The Man, The Legend… Father of Genetics

Gregor Mendel Priest who worked in the monastery garden Observed traits, or characteristics, of pea plants. Some were short or tall, had green or yellow seeds, etc. He did experiments on these pea plants for over ten years. etId=AC056D43-D1C AB9B- E564C7C74009&blnFromSearch=1&productcode=UShttp://player.discoveryeducation.com/index.cfm?guidAss etId=AC056D43-D1C AB9B- E564C7C74009&blnFromSearch=1&productcode=US

Pea Plants Pea plants are easy to study because their traits come in two forms (unlike human hair color). They also produce lots of offspring per generation, so he could get lots of data. They usually self-pollinate, but Mendel cross-pollinated them to chose the parents of a generation.

Purebred He would cross two plants with opposite traits, ex. One tall and one short. He picked purebred plants, which always produce offspring with the same trait as the parent. He called the parents the parental, or P, generation. The offspring were the first filial generation, or F 1.

Parents: 1 Tall & 1 Short F 1 generation was all tall F 2 generation was ¾ tall, ¼ short He did this for six other traits: seed shape, seed color, seed coat color, pod shape, pod color, and flower position. The “lost” trait always reappeared in ¼ of the F 2 generation! etId=7570E857-9BAE F- CF79EACA9201&blnFromSearch=1&productcode=DSChttp://player.discoveryeducation.com/index.cfm?guidAss etId=7570E857-9BAE F- CF79EACA9201&blnFromSearch=1&productcode=DSC

Inheritance Traits must come in pairs, with one from each parent. Some can hide others. Ex. Tall pea plant trait hides short pea plant traits Today, these traits are called genes. The different forms of genes are alleles. Ex. Each F 1 plant got one tall allele and one short allele.

Dominant & Recessive Traits Individual alleles control the inheritance of traits. Some are dominant and always show up. Others are recessive and are masked by the dominant trait. The tall allele was dominant over the short allele. Only plants that got 2 short alleles ended up short.

Hybrids The F 1 plants are hybrids b/c they have 2 different alleles for the trait In the F 2 generation, some got 2 short alleles and were short, some got 2 tall alleles and were tall, and some got 1 of each and were tall.

Genetic Symbols We use letters to represent alleles. The dominant allele is capitalized and the recessive is lower case. So a plant with_______ would be written like this _______ –2 Tall alleles, TT –1 tall, 1 short: Tt –2 short: tt

Father of Genetics He presented his work at the monastery, but others didn’t realize its significance. Since he wasn’t at a university, word of his work didn’t spread. He was forgotten for 34 years…. In 1900 his work was rediscovered and its importance realized. Now he’s considered the Father of Genetics.

Genetic Principles 1.Traits, or characteristics, are passed on from one generation of organisms to the next generation. 2.The traits of an organism are controlled by genes. 3.Organisms inherit genes in pair, one gene for each parent. 4.Some genes are dominant, whereas other genes are recessive. 5.Dominant genes hide recessive genes when both are inherited by an organism. 6.Some genes are neither dominant nor recessive. These genes show incomplete dominance.

Vocabulary 1.Gregor Mendel: father of genetics; studied pea plants 2.Genetics: scientific study of heredity, or the passing on of traits from an organism to its offspring 3.Dominant trait: the stronger trait (dominates recessive traits- always appears) **represented by a capital letter Ex: “T” would represent the gene, tallness 4.Recessive trait: the weaker trait (usually hidden by the dominant trait- seems to disappear) **represented by a lowercase letter Ex: “t” would represent the gene, shortness 5.Genes: set of instructions for each characteristic 6.Alleles: two forms of a gene 7.Phenotype: inherited appearance (brown hair) 8.Genotype: inherited combination of alleles (letters)

Vocabulary Notes 1.Gregor Mendel: ________________________________________________________________ 2. Genetics: ________________________________________________________________ 3. Dominant Trait: ___________________________________________________ Ex: _____________________________________________________________ 4.Recessive Trait: ___________________________________________________ Ex:______________________________________________________________ 5. Genes____________________________________________________________ _________________________________________________________________ 6. Alleles: _________________________________________________________________ _________________________________________________________________ 7. Phenotype: _________________________________________________________________ _________________________________________________________________ 8. Genotype: _________________________________________________________________ _________________________________________________________________