Mendels theory

GENETICS MENDELIAN THEORY OF INHERITANE

1. MENDELIAN THEORY OF INHERITANCE BY: Mrs.Keerthi Samuel Asso.professor Vijay marie con

2. INTRODUCTION Gregor Johann Mendel – father of Modern Genetics. He studied approximately 29000 pea plants to demonstrate inheritance of traits following certain laws. Observed characters like type of seeds , flower color and height of plants to show that one in every 4 pea plants has dominant pure bred and 2 has hybrid and 1/4 th shows recessive traits

3. WHY A PEA PLANT Flower structure of pea plant ensured self pollination and also well defined male and female characteristics. Single season crop Emasculation and pollination of pea plants is quiet easy. Reproduces sexually In varieties available , several characters has 2 contrasting forms which were easily distinguishable from each other

4. GENERATIONS OF PEA PLANTS

5. MENDELS LAWS OF INHERITANCE

6. I.LAW OF DOMINENCE Every gene has two alleles that can code for a trait This law  states that in a heterozygote, one trait will conceal the presence of another trait for the same characteristic. The recessive allele will remain “latent,” but will be transmitted to offspring by the same manner in which the dominant allele is transmitted. However this law is not fully accepted due to Codominance Incomplete dominance Over dominance

7. II.LAW OF SEGREGATION Mendel used 2 different varieties of seed shape. He crossed pea plant with round seed with peaplant with wrinkled seed WW ww –PARENT (P1) F1 GENERATION Ww Ww WW ww Ww Ww -F2 GENERATION

8. F2 W w W WW Ww w Ww ww In F1 generation all round plants were produced. When Crossed the F1 generation pea plants produced 2 different types of seeds in F2 generation. 3 out of 4 were round 1 was wrinkled. Then F2 generation was self pollinated to get F3 generation. In F3 generation 1/3 rd plants were round shaped 2/3 rd were round and wrinkled 1/3 rd were wrinkled So the overall ratio of round and wrinkled seeds is 3:1

9. INTRODUCTION CONCLUSIONS: There is equal contribution of both male and female parents for the development of characters in their offspring In f1 generation only dominant character is expressed. Recessive characters remain unchanged but is not expressed. In F2 generation characters of both parents were expressed as 3:1 Recessive character reappears in F2 generation which is identical to that of parents. Dominant character in F2 generation may be like that of parent (1/3) OR hybrid (2/3) II.LAW OF SEGREGATION

10. INTRODUCTION Law of inheritance states that allele pairs seperatess independently during gamete formation. As a result traits are transmitted to offspring independent of each other. Example: In this Mendel crossed 2 different varieties of pea plants that differ in cotyledon and seed color. 1 st variety: Green cotyledon and Yellow seeds(GGYY) 2 nd variety: yellow cotyledon and green seeds( ggyy ) Both were hybridized III.LAW OF INDEPENDENT ASSORTMENT

11. INTRODUCTION DIHYBRID CROSS GGYY X ggyy –P GENERATION GgYY – F1 GENERATION III.LAW OF INDEPENDENT ASSORTMENT

12. F2` GY Gy gY gy GY Gy gY gy STUDENT EXERSICE

13. F2` GY Gy gY gy GY GGYY GGYy GgYy GgYy Gy GGyY GGyy GgyY Ggyy gY GgYY GgYy ggYY ggYy gy GgyY Ggyy ggYy ggyy