Understanding Heredity and Genetics: From Early Ideas to Mendel's Laws

1. Phenotype and Genotype

2. Early Ideas About Heredity • Heredity: the passing of traits from parent to offspring

3. Early Ideas About Heredity • Blending inheritance: offspring are a blend of genetic material from both parents.

4. Early Ideas About Heredity • People thought genetic material mixed or blended like colors of paint.

5. Early Ideas About Heredity • If blended inheritance were correct, populations would eventually look alike over many generations.

6. Early Ideas About Heredity • Blending inheritance doesn’t explain why some traits skip a generation.

7. Gregor Mendel • Genetics: the study of how traits are passed from parents to offspring.

8. Gregor Mendel • Austrian monk with a fascination with biology • Conducted experiments by studying 7 different traits of pea plants.

9. Gregor Mendel • Recorded how the traits were passed from parent to offspring for several generations.

10. Gregor Mendel • Concluded that two “factors” control each trait.

11. Gregor Mendel • When organisms reproduce, each parent contributes one factor for each trait.

12. Dominant Factors • A genetic factor that “blocks” other factors is called dominant. • Represented by a capital letter (Y for yellow) (F for black fur)

13. Dominant Factors • A dominant trait is present if an organism has one or two dominant factors. YY or Yy FF or Ff

14. Recessive Factors • A genetic factor that is “hidden” by the dominant factor is called recessive. • Represented by a lowercase letter (y for green) (f for white fur)

15. Recessive Factors • A recessive trait is only present if an organism has two recessive factors. yy ff

16. Mendel’s Laws of Heredity • Law of segregation: the two “factors” for each trait separate from each other during meiosis.

17. Mendel’s Laws of Heredity • Law of independent assortment: the factors for one trait separate independently of how other factors separate

18. Mendel’s Laws of Heredity • Mendel didn’t know about DNA or how cells reproduce! • Still, his ideas formed the foundation of modern genetics.

19. Genes and Alleles • A gene is a section of DNA that has information about a trait in an organism.

20. Genes and Alleles • The different “types” or “versions” of a gene are called alleles. Y or y F or f

21. Genes and Alleles • Because eukaryotic chromosomes come in pairs, each gene has two alleles.

22. Genotype • The combination of alleles that an offspring gets from their parents is called its genotype. YY or Yy or yy FF or Ff or ff

23. Genotype • If both alleles in a genotype are the same, they are said to be homozygous. FF or ff

24. Genotype • If the two alleles in a genotype are different, they are said to be heterozygous. Ff

25. Phenotype • The observable traits of an organism are its phenotype.

28. What is the passing of traits from parent to offspring? • Inheritance • Heredity • Genetics • Allele

29. What do you call the combination of alleles in an organism? • Genes • Genotype • Phenotype • Factors

30. If the two alleles on a gene are the same, it is called • Homologous • Recessive • Heterozygous • Homozygous

31. What type of trait can only be seen if it is homozygous? • Inherited • Dominant • Recessive • heterozygous

32. What is the idea that inheritance of one trait is not influenced by inheritance of another trait? • Law of Independent Assortment • Law of Segregation • Law of Heredity • Law of Maternal Inheritance