Question

Question #1: Thomas Hunt Morgan used genetic mapping to map out genes on the chromosomes. He found that alleles that are not genetically linked, can still be on the same chromosome. Alleles A and Z are not genetically linked (recombination frequency is 50%) If the recombination frequency between different alleles are: AZ: 50% G-Z: 50% A-G: 8% T-D: 24% G-T: 39% TZ: 50% A-T: 47% DZ: 25% A. Are A and Z on the same chromosome? Why or why not? Use a diagram to explain this. (3 pts) (You may turn in the diagram separately in class, or try to draw one out digitally). B. How might you be able to figure out if they are on the same chromosome using Nucleic Acid Hybridization? (3 pts)

Answer 1

A. Frequency of recombination depends on distance between two genes on the chromosome. Hence chance of recombination is higher if two genes are very close to each other.

Recombination frequency lower than 50% indicates, the genes are linked. In our cas, the recombination frequency between gene A and Z is 50% hence A and Z genes are not on the same chromosome or may be very far from each other.

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Hence the genes are assort independently from each other (linked genes cannot assort independently)

B. with the help of nucleic acid hybridization, we can indentify whether both the genes are on same chromosome or not.

For the purpose, we can select some complementary sequences to both the genes which are labeled with fluorescent dye.

The technique is known as FISH, fluorescent insitu hybridization. the complementary sequences are hybridized on glass slide and fluorescent signal gives us result.