CHAPTER 11: INTRODUCTION TO GENETICS Section 11.1

Genome  Genome = All of an organism’s genetic material  Human Genome Project: the goal was to find out the sequence of the 3 billion nucleotide pairs that make up a human's genome.  Unless you have an identical twin, you have a unique genome that determines all of your traits

Key Words  Genetics: study of heredity, passing of characteristics from parent to offspring  Fertilization: during sexual reproduction male and female cells join  Trait: specific characteristic (ex: seed color, height, weight, etc.)

Key Words  Genes: factors passed from parent to offspring  Each gene has a locus, a specific position on a pair of homologous chromosomes.  Alleles: different forms of genes

Key Words  Hybrids: offspring of crosses of parents with different traits

Gregor Mendal  The “Father of Genetics”  Austrian Monk  Studied math and science at the University of Vienna  Worked in a monastery, there one of his jobs was caring for a garden  In this garden he carried out his genetics experiments

Pea Plants  Mendel used pea plants in his experiments  Pea plants are ideal:  Hundreds of offspring  For a plant reproduce quickly (several times in a growing season)  Easy to grow

Recap  Who is Gregor Mendel, what did he study?

Mendel’s Experiments  Mendel crossed several of his stock plants (starter plants)  These were true-breeding  Will always produce offspring with traits similar to themselves  Is a black cow that produces black calves true- breeding?  Is a black cow that produces some black calves and some brown calves true-breeding?

Mendel’s Experiments  Mendel crossed (bred) his true-breeding plants with other true-breeding plants  Cut off pollen bearing male parts to prevent self- pollination  Took pollen from one flower and dusted the female part on a different flower MethodsProcess: Cross-Pollination

Mendel’s Experiments  The first cross of the parents was the P- generation  The offspring is known as the F 1 generation  Mendel noticed that the offspring would have the characteristics of only one parent

Mendel’s Conclusions  What 2 conclusions could Mendel draw from his experiments?  1. Individual’s characteristics are determined by factors passed from one generation to another What are these factors called now? Genes  2. Principle of Dominance: some alleles are dominant and some are recessive

Dominant vs. Recessive  Alleles are represented by letters  Dominant alleles are represented by a capital letter R  Recessive traits are represented by a lower case letter r  Dominant alleles are expressed over recessive alleles  If you have to alleles together the dominant one will always be expressed or “visible”  Example: Height  Example: Brown hair

Segregation P-Generation F1F1 F2F2 F1F1

Segregation  How can we explain the fact that a short pea plant appeared in the F 2 generation?  Segregation: During gamete formation the alleles for each gene separate from each other so each gamete only has one allele for each gene.

Mendel’s 4 Findings 1. Inheritance of biological characteristics is determined by units known as genes 2. Principle of Dominance: some alleles are dominant while some alleles are recessive (masked) 3. Segregation: two copies of each gene (one from each parent) separate when forming gametes during meiosis (sex cells – sperm, egg) 4. Independent assortment: Alleles for different genes (different traits) usually separate independently of one another

QUESTIONS?????