The document discusses the concept of linkage, where genes located on the same chromosome tend to be inherited together. It notes that in a test cross of genes A and C located on the same chromosome, the F1 individual would only produce two types of gametes - those containing the parental combinations or those containing recombinant combinations, with parental combinations making up more than 50% of gametes. Linkage results in the formation of more parental phenotypes in the F2 generation compared to unlinked genes, which assort independently and produce recombinant phenotypes at a rate of 50%.

1. Linkage
Presented by:
Sanjay Kr. Vishwakarma

2. Linkage
• Test cross

3. Linkage
• Two genes involved in crossing are located on different chromosomes and exhibit
independent assortment

4. Linkage
• F1 individulal produce gametes of following types:
• All gametes are in equal proportion i.e., 1:1:1:1

5. Linkage
• Expected frequency after testcross will be

6. Linkage
• Let’s assume a case where A and C is located on the same chromosome

7. Linkage
• Testcorss of the F1 progeny
• F1 individual would produce only two types of gametes:

8. Linkage
• More than 50% gametes contain parental combinations and less than 50% gametes contain
recombinant combinations

9. Linkage

10. Linkage
• The genotype of a heterozygote is s+b+/sb.
• This arrangement is known as coupling state or cis-
configuration.
• Genotypic arrangement s+b/ sb+ is known as repulsion state or
trans-configuration.

11. Linkage

12. Conclusion
• A relationship among genes in the same chromosome; such genes tend to be inherited
together.
• This phenomena is known as linkage.

13. Multiple Choice Question

14. 1) Linkage results in
a) Formation of more Dominant phenotype
b) Formation of more Wild phenotype
c) Formation of more parental phenotype
d) Formation of more recombinant phenotype
Answer: c

15. 2) You cross a p+/v+ p+/v+ male drosophila to a p-/v- p-/v- and obtain the F1 hybrid. Now you
cross the F1 male with double recessive female. What will be the recombination phenotype in
F2?
a) p+/v+ p-/v- only
b) p+/v+ p-/v- and p-/v- p-/v-
c) p+/v+ p-/v- and p-/v- p-/v- also p+/v- p-/v- and p-/v- p-/v-
d) p+/v+ p-/v- and p-/v- p-/v- also p-/v+ p-/v- and p-/v- p-/v-
Answer: b

16. Thank You