Question

Look at the DNA sequence: | C | G | T | T | A | C | T | G | C | A | A | T | |---|---|---|---|---|---|---|---|---|---|---|---| | G | C | A | A | T | G | A | C | G | T | T | A |

Which sequence shows a substitution mutation?

Responses
Option 1: This sequence replaces the 4th base pair (T-A) with (G-C). | C | G | T | G | A | C | T | G | C | A | A | T | |---|---|---|---|---|---|---|---|---|---|---|---| | G | C | A | C | T | G | A | C | G | T | T | A |

Option 2: This sequence shows an insertion mutation (adding an extra C-G base pair), making the chain longer. | C | G | T | C | T | A | C | T | G | C | A | A | T |

Option 3: This sequence is an exact match to the original DNA sequence provided in the prompt. | C | G | T | T | A | C | T | G | C | A | A | T |

Option 4: This sequence shows a deletion mutation (removing the 4th base pair), making the chain shorter. | C | G | T | A | C | T | G | C | A | A | T |

Answer 1

Option 1.

Explanation: A substitution changes one base pair to a different base pair without changing sequence length. Option 1 replaces the 4th base pair (T–A) with G–C while keeping the strand length the same. Option 2 is an insertion (longer), Option 4 is a deletion (shorter), and Option 3 is unchanged.