2.2.3 Exercise: Comparing sequences

1 Comparing sequences using GC content

You have five DNA strands, but you don’t know the actual sequences.

1. 0.45
2. 0.55
3. 0.50
4. 0.45
5. 0.55

1.1 Question 1

Using only the GC content as criterium, which ones of these sequences may actually be the same?

1.2 Question 2

Sort these sequences, from the least heat-resistant to the most heat-resistant.

1.3 Question 3

Write a sequence that has a GC content of 0.4.

2 Comparing sequences using nucleotides

You have three DNA strands:

1. TACGTATGCT
2. ATGCCGTAAC
3. GCTACGGATC

2.1 Question 4

Calculate the GC content for each sequence. Are they similar or not?

2.2 Question 5

Draw dot plots comparing all sequences. You should have three dot plots, comparing 1-2, 1-3 and 2-3. Draw the first one vertically, and the second one horizontally.

2.3 Question 6

For each pair of sequences, write the common subsequences between them that have at least three nucleotides. Use the dot plot to find these subsequences.