Question

in almost 70% of cystic fibrosis cases, a set of three base pairs is lost from chromosome 7. this results in the loss of an amino acid in the cftr gene, causing cystic fibrosis.
what type of mutation is described?
substitution
delation
nondisjunction
translocation

Explanation:

• Substitution: involves replacing one base pair with another. But the problem states a set of three base pairs is lost, not replaced.
• Deletion: occurs when one or more base pairs are removed from the DNA sequence. Here, three base pairs are lost, which fits the definition of deletion.
• Nondisjunction: is related to the failure of chromosomes to separate properly during cell division, not about loss of base pairs.
• Translocation: is the transfer of a segment of DNA from one chromosome to another (non - homologous chromosome), not about loss of base pairs.

Answer:

deletion