Genetics Inheriting Traits I Inheriting Traits A An

Genetics: Inheriting Traits

I. Inheriting Traits • A. An organism’s characteristics is the collection of many traits inherited from its parent(s) • 1. Heredity- passing of traits to offspring • B. Traits are determined by genes on chromosomes – 1. Alleles are different forms of a trait

II. What is Genetics? • A. Genetics- the study of how traits are inherited through the interactions of alleles • B. Gregor Mendel “The Father of Genetics” 1 st to trace one trait through several generations. – 1. Mendel used pea plants and probability to explain the process

Mendel “The Father of Genetics” ▣ Mendel was a monk ▣ When he was a young child he loved plants ▣ Work with thousands and thousands of plants during his lifetime

III. Mendel’s Garden • A. Mendel knew that parts of a plant produced pollen the male sperm and other parts female similarly produced eggs cells. When these 2 cells came together it was called fertilization and developed into an embryo. – 1. Most of his plants would self pollinate themselves creating children that had identical physical characteristics from their single parent this is known as true-breeding. • Mendel was curious to produce seeds from 2 different plants or cross-breeding

III. Mendel’s Garden ▣ B. Mendel crossed two plants with different expressions of a trait (a specific characteristic). � 1. New plants from the crosses looked like one of the two parents he called hybrids Ex. Tall Pea plant mate with a Short pea plant = Tall pea plant offspring **Note: Why are all the offspring Tall and not Short?

III. Mendel’s Garden cont. • C. Mendel noticed when cross-breeding plants some traits seemed to disappear while others were always present – 1. Traits (alleles) that are always present and seem to cover up the other trait are dominant – 2. Traits (alleles) that seem to disappear or are “covered up” are recessive

IV. Segregation • A. Mendel wanted to answer his own questions did all the recessive traits disappear – 1. He took the offspring from the 1 st cross and crossed them with one another – 2. The result…the recessive traits reappeared In conclusion • B. When gametes are produced the 2 alleles segregate from each other so that each gamete (sperm/egg) carries a single copy of each gene.

V. Using Probability • A. Using probability helps you determine or predict what a cross’ offspring will look like. In other words which gametes will come together • B. Punnett squares- a tool to help predict and compared genetic variations that will result from a cross Parent 1 X Parent 2 Allele 1 Allele 2

V. Using Probability cont. • C. The Alleles are represented by Upper and Lowercase letters – 1. Uppercase letters =dominant traits – 2. Lowercase letters =recessive traits

VI. Alleles Determine Traits ▣ A. Every cell in your body has at least two alleles for every trait located on chromosomes. � 1. If an organism has two of the same alleles the trait is known as homozygous �A. Ex. TT or tt � 2. If an organism has two alleles that are different it is known as heterozygous �A. Ex. Tt ▣ B. The two letters for each trait (genetic make up) is called the genotype. ▣ C. The way an organisms looks is known as the phenotype.

VII. Punnett Squares • A. Place two alleles for one parent on the top and the two alleles for the second parent along the side • B. The square is then filled in with one allele donated by each parent Parent 1 X Allele 1 Parent 2 Allele 1 Allele 2

VII. Punnett Square cont. �C. Cross a Tall plant homozygous dominant with a Short homozygous recessive plant Tall Plant Short Plant X T T t Tt Tt �What is the probability the plants will be Tall? Short?

Lets Practice • Heterozygous Tall pea plant with Heterozygous Tall pea plant • Heterozygous Tall pea plant with a homozygous recessive short pea plant • Homozygous Tall pea plant with a heterozygous Tall pea plant