Question

question 15
2 pts
transition and transverse substitutions are
○ mutations only caused by chemicals such as benzene or radiation such as x-rays.
○ purine-to-purine/pyrimidine-to-pyrimidine and purine-to-pyrimidine/pyrimidine-to-purine replacement, respectively.
○ purine-to-purine and pyrimidine-to-pyrimidine, respectively.

question 16
2 pts
how could you determine the distance between two genes using experimental matings?
○ look for the incidence of mutations
○ look for the frequency of crossing over between the genes
○ look for the amount of non-disjunction in the cell

Explanation:

Question 15

• Option 1: Mutations can be caused by various factors, not just chemicals/radiation, so this is wrong.
• Option 2: Transition is purine - to - purine or pyrimidine - to - pyrimidine substitution, and transversion is purine - to - pyrimidine or pyrimidine - to - purine substitution. This matches the definitions.
• Option 3: This misdefines transversion, so it's incorrect.

• Option 1: Mutations don't directly indicate gene distance, so this is incorrect.
• Option 2: The distance between two genes is related to the frequency of crossing over between them (recombination frequency). Higher frequency means shorter distance (or vice versa, depending on scale), so this is correct.
• Option 3: Non - disjunction is about chromosome segregation errors, not gene distance, so this is wrong.

Answer:

B. purine - to - purine/pyrimidine - to - pyrimidine and purine - to - pyrimidine/pyrimidine - to - purine replacement, respectively.

Question 16