Genetics

1. Genetics

2. What is Genetics? • Genetics is a branch of biology that studies how characteristics are passed from one generation to the next

3. Important Terminology • Trait – characteristic that can vary from one organism to another and in passed from parent to offspring • Genes – biological inheritance is determined by factors passed from one generation to the next • Alleles – a gene that occurrsin two contrasting forms that produced different characteristics (different versions of a gene) • Dominant – trait that will always be expressed if the offspring inherits it • Recessive – trait that is “hidden” if the dominant trait is present

4. Gregor Mendel • Mendel was an Austrian monk who studied math and science and taught science in a monastery • Performed experiments as he maintained the monastery garden • Performed the first scientific study of inheritance on pea plants

5. Mendel’s Experiments • Mendel used pea plants for many of his experiments • Parts of the flowers for reproduction • Pollen = male sex cells • Eggs in flower = female sex cells • Pea plants normally reproduce by self-pollination • Pollen fertilizes flower of the same plant • True-breeding pea plants (“pure bred”) • Would the new plants be identical or different than the parent? Why?

7. Mendel’s Experiments • Pea plants can cross-pollinate • Pollen fertilizes flower of a different plant • New plants have two parent plants • Infer if the new plants would be identical or different from the parents. Why? Mendel cross-pollinated pea plants!

8. Mendel’s Experiments • The first generation was called the P (Parental) Generation • These were the original pairs of plants • The second generation was called the F1 (Filial 1) Generation • These plants were the first offspring • The third generation was called the F2 (Filial 2) Generation • These plants were the offspring of the first offspring

9. Mendel’s Observations • Some traits were observed in the F1 generation • Some traits seemed to “skip” a generation and show up 2 generations later in the F2 generation

12. Mendelian Genetics • Traits that seem to “skip” a generation are recessive traits • These traits are “masked” by the dominant traits • The plants that had the trait but it could not be seen are called carriers

13. Mendel’s Laws of Inheritance • Law of Dominance • If the dominant trait is present, it will always be expressed • The recessive trait will be masked by the dominant trait

14. Mendel’s Laws of Inheritance • Law of Segregation • Alleles (different forms of a gene) will separate during meiosis

15. Mendel’s Laws of Inheritance • Law of Independent Assortment • Traits are not dependent on other traits to be inherited • Ex: having a baby with brown eyes does not mean he/she will have brown hair

16. Homosygous or Heterozygous? • Homozygous – the organism will have two dominant alleles for a certain trait or two recessive alleles • Ex: TT or tt • Heterozygous – the organism will have one dominant and one recessive allele for a trait • Ex: Tt