1. Heredity and the Environment Why do you look so much like your parents?

2. Heredity What is heredity? How do humans, plants, and animals pass on traits to their offspring? Does the environment affect heredity? Click on key words for the definition.

3. Vocabulary Recessive trait Dominant trait Genes Alleles Genotype Phenotype DNA

4. Mendelian Genetics In the 1860s, Gregor Mendel worked with garden pea plants and helped scientists begin to understand heredity. Click Here to find out more about Mendel’s work. Be sure to look at the animation.

5. Mendel’s First Experiments Mendel used true-breeding plants in his experiments. True-breeding plants will always look like the parent plant. Mendel bred, or crossed, true-breeding plants with different traits. Mendel got similar results for each of the crosses he made.

6. Mendel’s First Experiments It seemed that one trait could be hidden by the other. Mendel called the trait that seemed to disappear the recessive trait and the trait that always appeared the dominant trait.

7. Mendel’s Second Experiments Mendel wanted to figure out what happened to the recessive traits. So he allowed the first- generation plants to self-pollinate. Some of the offspring of these crosses had the trait that had disappeared in the first cross.

8. Mendel’s Second Experiments No matter which characteristic Mendel studied, the recessive trait reappeared in the second generation. How could they do that?

9. A Stroke of Brilliance Mendel knew that his results could be explained only if each plant had two sets of instructions for each characteristic. Scientists now call these instructions genes. The different forms of each gene are known as alleles. Click Here to find out more about Mendel’s work. Be sure to look at the animation

10. The Proof Is in the Punnett Square A Punnett square is a diagram that shows all of the possible combinations of alleles from the parents. Dominant alleles are represented by capital letters, and recessive alleles are represented by lowercase letters.

11. The Proof Is in the Punnett Square

12. The squares inside the Punnett square contain the possible allele combinations for the offspring. The inherited combination of alleles is the offspring’s genotype. Phenotype is an organism’s appearance.

13. Review The allele for a cleft chin, C, is dominant among humans. What would the results be from a cross between a woman with the genotype Cc and a man with the genotype cc? Use a Punnett square to make your predictions. Click Here for help with Punnett Squares Click Here for help with Punnett Squares

14. DNA The code to life

15. The Code to Life What if you could discover a way to prevent aging? What if you could discover a way to prevent aging? What causes cancer? What causes cancer? What if the secret is inside every one of the cells of our bodies? What if the secret is inside every one of the cells of our bodies?

16. Genes and DNA Scientists know that traits are determined by genes. And they know that genes are passed from one generation to the next. Genes are parts of a molecule called DNA. DNA is short for deoxyribonucleic acid.

18. Genes and DNA Click Here for more about DNA Click Here for more about DNA If you are still interested, find out how they discovered DNA by Clicking Here. If you are still interested, find out how they discovered DNA by Clicking Here. Check out the animation. Check out the animation.

19. The Importance of Environment It’s important to remember that genes aren’t the only influences on your development. Many things in your environment influence how you grow and develop. Think about how important a healthy diet and exercise are.

20. The Importance of Environment Your genes may make it possible that you will grow to be tall. But you need to eat right to reach your full potential height. You may have inherited a special talent. But you need to practice that talent.

21. Works Cited Biologically Speaking: Genetics and Heredity. AIMS Multimedia. 2004. DigitalCurriculum. 2 February 2005 Biologically Speaking: Genetics and Heredity. AIMS Multimedia. 2004. DigitalCurriculum. 2 February 2005 Holt Science & Technology Holt, Rinehart and Winston Holt Science & Technology Holt, Rinehart and Winston

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23. Vocabulary Heredity is the passing of traits from one generation to the next. A trait is an inherited physical characteristic.