Genetics

1. Genetics The Science of Heredity

2. What does heredity mean? • Inheritance: The process of passing on traits from parents to offspring. • Heredity: The passing of physical characteristics from parent to offspring. • Traits: Characteristics (examples):

3. Gregor Mendel Mendel was a famous geneticist, he laid the foundation of genetics today. Much of what we have discovered can be attributed to Mendel’s work with peaplants

4. The Year was 1861 • Gregor Mendel was a young priest from a monastery in Central Europe. • He attended the University of Vienna to study mathematics and science. • He then returned to the monastery to teach at a nearby high school. • Mendel also cared for the monastery’s garden, where he began to become curious about how plants of the same species had different characteristics or traits. For example, some pea plants grew tall while others grew short.

5. Understanding Vocabulary • Traits: characteristics • Heredity: The passing of traits from parents to offspring. • Genetics: The study of heredity • Purebred: one that always produces offspring with the same form of a trait as the parent. (homozygous) • Hybrid: has both forms of a trait (heterozygous)

6. Generations P-Generation (Parents) F1 Generation (1st Generation of Parents P) F2 Generation (2nd Generation of Offspring F1)

7. Genes are factors that control traits • Different forms of genes are called alleles. • Each offspring inherits a combination of two alleles from its parents. • Individual alleles control the inheritance of traits. • Some alleles are dominant and other alleles are recessive.

8. Dominant Alleles • A dominant allele is one that can be seen in the phenotype (physical characteristics).

9. Recessive Alleles • Recessive alleles are masked or covered up by the dominant alleles and cannot be seen in the phenotype.

10. Hybrid • An organism that contains two different alleles for a trait. (heterozygous)

11. Using Symbols in Genetics • Geneticists today use a standard shorthand method to write about alleles in genetic crosses. • Instead of using words such as “tall” to represent an allele they use letters. • A dominant allele is represented by capital letters • A recessive allele is represented by lowercase letters.

12. Let’s refresh! • TT= both dominant alleles, also known as a purebred or homozygous. • tt= both recessive alleles, also known as homozygous. • Tt= a dominant allele and a recessive allele are present. Also known as a hybrid or heterozygous.

13. Genotype vs Phenotype • Genotype: genetic makeup (BB,Bb,bb) • Phenotype: physical makeup (brown eyes or blue eyes, tall or short)

14. Punnett Squares • The gene combinations that might result from a genetic cross can be determined by drawing a diagram known as the punnett square. • Capital Letter represents the dominant allele. • Lowercase letter represents the recessive allele.

15. Punnett Square Parent 1 ( Bb) Parent 2 (Bb)

16. Try These! • TT X tt • Bb x bb • BB x bb • Tt x Tt

17. Genotype vs Phenotype • Genotype is an organisms genetic makeup. For example Bb or BB or bb • Phenotype is the physical characteristics or what they look like. For example if we were talking about eye color, the phenotype would be blue or brown eyes. • If B =brown eyes and b= blue eyes • Bb=would have brown eyes • BB= brown eyes • bb = blue eyes

18. Beyond Dominant and Recessive Alleles • Some alleles are neither dominant or recessive, and many traits are controlled by multiple alleles or multiple genes. • Incomplete dominance: one allele is not completely dominant over another. A red flower crossed with a white flower, produce pink flowers. (blending) • Codominance: Both alleles contribute to the phenotype of the organism. Black chicken crossed to a white chicken produce a black and white chicken

19. Homozygous vs Heterozygous • Homozygous and purebred = BB • Heterozygous and hybrid= Bb