2. heredity genetics dominant recessive gene law of segregation law of independent assortment 4.1 Foundations of Genetics allele phenotype genotype homozygous heterozygous

3. Early Ideas About Heredity Combined genetic material from a sperm and an egg determines the traits or features of an offspring. 4.1 Foundations of Genetics Heredity is the passing of traits from parents to offspring.

4. Early Ideas About Heredity (cont.) The idea of blending inheritance is offspring are a blend of genetic material from both parents. 4.1 Foundations of Genetics –The genetic material mixed or blended like colors of paint. –Over many generations, populations would eventually look alike. –Blending inheritance cannot explain why some traits skip a generation.

5. Gregor Mendel and His Experiments Gregor Mendel was the first to record evidence that traits are determined by factors passed from parents to offspring. Mendel established the basic laws of heredity. Genetics is the study of how traits of organisms are passed from parents to offspring. 4.1 Foundations of Genetics

6. Mendel’s Experimental Methods Mendel conducted breeding experiments by studying seven traits of pea plants and each traits had only two variations. 4.1 Foundations of Genetics

7. Mendel’s Experimental Methods (cont.) 4.1 Foundations of Genetics

8. Controlled Experiments Mendel controlled fertilization in the pea plants, allowing him to see how traits pass from one generation to another. 4.1 Foundations of Genetics Mendel allowed some flowers to self-fertilize. He also performed cross-fertilization by transferring pollen from one pea flower to another.

9. Mendel’s Unique Methods Used true-breeding plants for each trait— plants that always produce offspring with that trait when they self-pollinate 4.1 Foundations of Genetics Recorded the inheritance of traits for several generations Used a mathematical approach

10. Mendel’s Experimental Results Mendel concluded that two factors control each inherited trait. 4.1 Foundations of Genetics When organisms reproduce, each gamete— sperm or egg—contributes one factor for each trait.

11. Dominant Factors A genetic factor that blocks another genetic factor is called dominant. 4.1 Foundations of Genetics A dominant trait is observed when offspring have one or two dominant factors.

12. Recessive Factors A genetic factor that is hidden by the presence of a dominant factor is recessive. 4.1 Foundations of Genetics A recessive trait can be observed only when two recessive genetic factors are present in offspring.

13. Mendel’s Laws of Heredity Law of segregation: the two factors for each trait segregate—separate from each other—during meiosis when gametes form 4.1 Foundations of Genetics Law of independent assortment: the factors for one trait separate independently of how factors for other traits separate

14. Modern Definitions of Mendel’s Ideas Mendel did not know about DNA or how cells reproduce, but his ideas about inheritance are still true today. 4.1 Foundations of Genetics

15. Genes and Alleles A gene is a section of DNA that has information about a trait in an organism. 4.1 Foundations of Genetics Each form of a gene with different information is called an allele.

16. Genes and Alleles (cont.) 4.1 Foundations of Genetics

17. Phenotype and Genotype The observable traits and all characteristics of an organism make up the organism’s phenotype. 4.1 Foundations of Genetics The alleles that make up an organism is the organism’s genotype. The alleles of a particular gene is that gene’s genotype.

18. Homozygous and Heterozygous Genotypes Because eukaryotes have pairs of chromosomes, a genotype for a gene has two alleles. 4.1 Foundations of Genetics If the two alleles have the same information, the genotype is homozygous. If the two alleles have different information, the genotype is heterozygous.

19. Homozygous and Heterozygous Genotypes (cont.) 4.1 Foundations of Genetics

20. Law of Segregation Explained The movement of chromosomes during meiosis explains Mendel’s law of segregation. –Each set of chromatids separates into different gametes during meiosis II. –Each gamete receives only one allele. 4.1 Foundations of Genetics

21. Law of Segregation Explained (cont.) 4.1 Foundations of Genetics

22. Law of Independent Assortment Explained The daughter cells produced by meiosis receive only one chromosome from each pair of homologous chromosomes. –A daughter cell might receive the A or a chromosome from pair 1 and the B or b chromosome from pair 2. –This results in four possible allele combinations for two homologous pairs of chromosomes. 4.1 Foundations of Genetics

23. Law of Independent Assortment Explained (cont.) 4.1 Foundations of Genetics

24. Importance of Mendel’s Genetic Studies In the 1860s, no one knew about chromosomes or meiosis so it was hard to understand Mendel’s discoveries. All the research of modern genetics is based on Mendel’s conclusions from his work with pea plants. 4.1 Foundations of Genetics

25. Lesson 1 Review What is the passing of traits from parents to offspring called? Ainheritance Bgenetics Cheredity Dallele 4.1 Foundations of Genetics 1.A 2.B 3.C 4.D

26. Lesson 1 Review What are the alleles that make up an organism called? Agenes Bgenotype Cphenotype Dfactors 4.1 Foundations of Genetics 1.A 2.B 3.C 4.D

27. Lesson 1 Review If two alleles for a gene have the same information, what kind of genotype does that gene have? Ahomologous Brecessive Cheterozygous Dhomozygous 4.1 Foundations of Genetics 1.A 2.B 3.C 4.D