Back cross and test cross

Explains Back cross and test cross and their application

1. BACK CROSS & TEST CROSS Dr. Valli Syam

2. Backcrossing  is a crossing of a  hybrid  with one of its  parents  or an individual genetically similar to its parent, in order to achieve offspring with a genetic identity which is closer to that of the parent. It is used in horticulture, animal breeding and in production of  gene knockout  organisms. Backcrossed hybrids are sometimes described with  acronym  "BC", for example, an  F1 hybrid  crossed with one of its parents (or a genetically similar individual) can be termed a BC1 hybrid, and a further cross of the BC1 hybrid to the same parent (or a genetically similar individual) produces a BC2 hybrid.

3. Yy yy YY Y y Y y YY Yy Yy yy Y y Y y Parental Generation Gametes F1 Generation Gametes F2 Generation Phenotypic ratio 3 : 1 Yellow : Green Genotypic ratio 1 : 2 : 1 YY Y y yy Homozygous Heterozygous Homozygous Dominant Recessive MONOHYBRID CROSS

4. Yy yy YY Y Y Y y Y y Y y Parental Generation Gametes F1 Generation Gametes BACK CROSS F1 P If the F1 is crossed with Dominant parent

5. Yy yy YY Y Y Y y YY Y y Y y Parental Generation Gametes F1 Generation Gametes BACK CROSS F1 P If the F1 is crossed with Dominant parent

6. Yy yy YY Y Y Y y YY YY Y y Y y Parental Generation Gametes F1 Generation Gametes BACK CROSS F1 P If the F1 is crossed with Dominant parent

7. Yy yy YY Y Y Y y YY YY Yy Y y Y y Parental Generation Gametes F1 Generation Gametes BACK CROSS F1 P If the F1 is crossed with Dominant parent

8. Yy yy YY Y Y Y y YY YY Yy Y y Y y Parental Generation Gametes F1 Generation Gametes BACK CROSS Yy F1 P If the F1 is crossed with Dominant parent

9. Yy yy YY Y Y Y y YY YY Yy Y y Y y Parental Generation Gametes F1 Generation Gametes BACK CROSS Yy F1 P If the F1 is crossed with Dominant parent Phenotypic ratio All Yellow seed Genotypic ratio 1 : 1 YY Y y

10. Yy yy YY y y Y y Y y Y y Parental Generation Gametes F1 Generation Gametes F2 Generation If the F1 is crossed with Recessive parent BACK CROSS F1 P

11. Yy yy YY y y Y y Yy Y y Y y Parental Generation Gametes F1 Generation Gametes F2 Generation If the F1 is crossed with Recessive parent BACK CROSS F1 P

12. Yy yy YY y y Y y Yy Yy Y y Y y Parental Generation Gametes F1 Generation Gametes F2 Generation If the F1 is crossed with Recessive parent BACK CROSS F1 P

13. Yy yy YY y y Y y Yy Yy yy Y y Y y Parental Generation Gametes F1 Generation Gametes F2 Generation If the F1 is crossed with Recessive parent BACK CROSS F1 P

14. Yy yy YY y y Y y Yy Yy yy Y y Y y Parental Generation Gametes F1 Generation Gametes F2 Generation If the F1 is crossed with Recessive parent BACK CROSS yy F1 P

15. Yy yy YY y y Y y Yy Yy yy Y y Y y Parental Generation Gametes F1 Generation Gametes F2 Generation If the F1 is crossed with Recessive parent Phenotypic ratio Yellow : Green Genotypic ratio 1 : 1 Y y yy BACK CROSS yy F1 P

16. Yy yy YY y y Y y Yy Yy yy Y y Y y Parental Generation Gametes F1 Generation Gametes F2 Generation If the F1 is crossed with Recessive parent Phenotypic ratio Yellow : Green Genotypic ratio 1 : 1 Y y yy This is also called TEST CROSS BACK CROSS yy F1 P

17. REFERENCES Genetics – VB Rastogi – 4 th Edition – Medtech Publishers -2019 Cell Biology, Genetics, Molecular Biology, Evolution And Ecology - P.S. Verma &V.K. Agarwal - S. Chand & Company Ltd. 2005 https://en.wikipedia.org/wiki/Backcrossing#:~:text=Backcrossing%20is%20a%20crossing%20of,production%20of%20gene%20knockout%20organisms.