BioinformaticsLesson 1 of 3 in the course Sequence alignment

Sequence Alignment: Methods, Scoring, and Interpretation

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

Sequence alignment arranges DNA, RNA, or protein sequences so that corresponding residues can be compared. It helps researchers identify similarities that may reflect shared function, structure, or evolutionary history.

Sequence 1: A C G T A C Sequence 2: A C - T G C

The dash represents a gap. It is not a nucleotide; it marks a position introduced in the alignment to represent a possible insertion or deletion in the sequences’ histories.

All flashcards

Global alignment
An alignment method that attempts to compare sequences across their full lengths.
Local alignment
An alignment method that finds a high-similarity region within sequences that may differ overall.
Pairwise alignment
Comparison of two sequences to find a strong global or local match.
Substitution matrix
A table assigning scores to amino-acid substitutions in protein alignments.
Alignment credibility
How similar the best-scoring alignment is to plausible alternative alignments of the same sequences.

Quiz questions

  1. What does statistical significance assess for a sequence alignment?Answer: How likely an alignment of that quality is to occur by chance in a specified search context.
  2. How do heuristic word methods such as BLAST accelerate sequence searches?Answer: They identify promising candidates using short matching words before more detailed alignment.
  3. How does a progressive multiple-sequence alignment method generally build an alignment?Answer: It aligns similar sequences first, then adds other sequences or groups step by step.
  4. What information does structural alignment use to compare proteins or RNA molecules?Answer: Known three-dimensional structural information, rather than sequence alone.
  5. When a sequence is plotted against itself in a dot-matrix plot, what can off-diagonal lines reveal?Answer: Repeated regions within the sequence.

Based on the Wikipedia article Sequence alignment, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.

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