Gregor Mendel Father of Genetics: Principles of biological and hereditary traits

Gregor Johann Mendel  Austrian monk  Studied the inheritance of traits in pea plants  Developed the laws of inheritance  Mendel's work was not recognized until the turn of the 20th century

Gregor J. Mendel  Between 1856 and 1863, Mendel cultivated and tested thousands of pea plants  He found that the plants' offspring retained traits of the parents

Vocab To Keep in mind Heredity- the passing of traits from parent to offspring. Self-pollinate- A plant is often able to pollinate by itself because it contains both the male and female reproductive structures. This only requires 1 parent. Dominant trait- the trait observed when at least one dominant allele for a characteristic is inherited Recessive trait- a trait that is apparent only when two recessive alleles for the same characteristic are inherited Genes- a segment of DNA that carries hereditary instructions and is passed from parent to offspring Alleles- multiple forms of the same gene Genotype- an organisms inherited combination of alleles Phenotype- an organisms inherited appearance

Inheritance  Mendel stated that physical traits are inherited as “particles”  Mendel did not know that the “particles” were actually Chromosomes & DNA  Chromosome:  Chromosome: a threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.  Gene:  Gene: a unit of heredity that is transferred from a parent to offspring and is held to determine some characteristic of the offspring.

Why grow peas?  Can be grown in a small area  Produce lots of offspring  Produce pure plants when allowed to self- pollinate several generations  Can be artificially cross-pollinated

Mendel’s tests Mendel tested 7 traits: 1.Flower color 2.Flower position 3.Seed color 4.Seed shape 5.Pod shape 6.Pod color 7.Plant height

The Peas Mendel crossed flowers that were true-breeding for each characteristic. He crossed a purple (PP) flowered plant with a white (pp) flowered plant. (Parent Generation)

The Peas cont’d The first generation (F1) of plants all had purple flowers. Where did the white color go?? (Pp) (Pp) (Pp.) (Pp) Purple Parent (Pp)

The Peas cont’d Mendel took two of his first generation (F1 x F1) purple flowered plants and crossed them together. In the second generation (F2) he had 3 purple flowered plants, and 1 white flowered plant. (PP) (Pp) (pp) Purple Parent (Pp)

Mendel & The Peas Mendel noticed in the first generation, all of the white flowers seemed to disappear. He called this a recessive trait. The white color faded into the background at first. It showed up in the next generation when he pollinated the flowers.

Mendel & The Peas The color (purple) that seemed to mask over the recessive color was named the dominant trait.

Traits Mendel was responsible for figuring out that each plant carried two sets of instructions for each characteristic (one from the “mom” and one from the “dad”). Trait- a distinguishing quality or characteristic, typically one belonging to a person

Test your knowledge 1. If you crossed a true-breeding black rabbit with a true-breeding white rabbit, all of the offspring would be black. Which trait is dominant in rabbits: black fur or white fur? Which trait is recessive?

And the answer is…. The trait for black fur is dominant over the trait for white fur. The white fur trait is recessive. (Bb) (Bb) (Bb) White Rabbit (bb) Black Rabbit (BB)

Review Heredity- the passing of traits from parent to offspring. Self-pollinate- A plant is often able to pollinate by itself because it contains both the male and female reproductive structures. This only requires 1 parent. Dominant trait- the trait observed when at least one dominant allele for a characteristic is inherited Recessive trait- a trait that is apparent only when two recessive alleles for the same characteristic are inherited Genes- a segment of DNA that carries hereditary instructions and is passed from parent to offspring Alleles- multiple forms of the same gene Genotype- an organisms inherited combination of alleles Phenotype- an organisms inherited appearance

Any last questions???