Genetics!

1. Genetics!

2. Gregory Mendel • Born 1822; Died 1884 • Monk and a teacher • Work not recognized until 1900 • Studied heredity by studying pea plants • What is heredity?

3. MENDEL’S PEA PLANTS • Observed seven characteristics of pea plants with two different traits • Controlled how each plant was pollinated • Self-pollination or cross-pollination • What’s the difference?

4. MENDEL’S EXPERIMENTS • Grew true-breeding plants • What does it mean to be true breeding? • Starting strain called parent generation or P generation • Cross-pollinated P generation to produce offspring called the first filial generation or F1 generation • F1 generation self-pollinated and produce the second filial generation or F2 generation

5. P generation x

6. P generation x All of the F1 showed one color F1 generation

7. P generation x F1 generation F2 produced plants about ¾ one trait and ¼ the other trait F2 generation

8. Results • Factor was controlling the traits since there were two traits there were two factors • Alleles: represent the factors - dominant CAPITAL LETTERS; recessive lower case letters; They are alternate forms of genes. • Dominanttrait: Able to repress the other trait • Recessivetrait: repressed by the dominant • Homozygous: same alleles; RR or rr – also called purebred or true breeding • Heterozygous: one of each allele forming a hybrid Rr • Genotype: allele pairs/actual DNA: RR, Rr, or rr • Phenotype: physical appearance; red, yellow, green, tall, short, etc. *You only see the recessive phenotype when there are two of the recessive alleles. Whenever you see the dominant phenotype, you cannot tell the genotype.* • Lead to the modern study of molecular genetics, the study of chromosomes and genes. Y y

9. Laws of Genetics • LawofSegregation: a pair of factors is segregated or separated during the formation of gametes (i.e. the homologous chromosomes are separated during anaphase I of meiosis I into different gametes.) • LawofIndependentAssortment: factors for different characteristics are distributed to gametes independently – factor for different traits do not follow each other into the same gamete

10. Probability • Probability that a specific event will occur; expressed as a decimal, fraction, or percent • Probability = Number of times an event happened Number of possible opportunities • The predicted results are more likely to occur the more trials that are performed

11. Monohybrid Crosses • Monohybrid cross: between individuals with one pair of contrasting traits ( mono = one) • Punnett squares are used to help predict the probability of a trait

12. Homozygous x Homozygous • Crossing two plants homozygous for color (P) • One dominant one recessive • PP x pp • Genotype • 4 Pp • Phenotype • 4 purple

13. Homozygous x Heterozygous • Crossing a homozygous dominant with a heterozygous plant for color (P) • PP x Pp • Genotype • 2 PP • 2 Pp • Phenotype • 4 purple

14. Homozygous x Heterozygous • Crossing a heterozygous plant with a homozygous recessive for color (P) • Pp x pp • Genotype • 2 Pp • 2 pp • Phenotype • 2 purple • 2 white

15. Heterozygous x Heterozygous • Both heterozygous for color (P) • Pp x Pp • Genotype • 1 PP • 2 Pp • 1 pp • Phenotype • 3 purple • 1 white

16. Testcross • Used to determine the genotype of a individual with an unknown genotype • Must use an organism of an known genotype hence use a homozygous recessive