Question

Below is a small segment from a file containing a DNA sequence: Information Flag question AGATAGA Consider the problem of counting all length-3 sequences, including overlapping sequences, i.e., the number of occurrences of AGA, GAT, ATA, ... using Map-Reduce. For the above DNA segment: Question 3 What are ALL the key, value pairs output by the Map step: Not yet answered Points out of 1.00 Select one: O a. (AGA, 2), (GAT, 1), (ATA, 1), (TAG, 1) O b. (AGA, 3), (GAT, 3), (ATA, 3), (TAG, 3) O C. (AGA, 1), (GAT, 1), (ATA, 1), (TAG, 1), (AGA, 1), (GAT, 1), (ATA, 1), (TAG, Flag question 1) O d. (AGA, 1), (GAT, 1), (ATA, 1), (TAG, 1), (AGA, 1)

Answer 1

3. d

• The map function will count all the break the DNA sequence into 3 length sequence and count as 1.
• AGATAGA, it will start from the first letter and will run for the three letters and hence, (AGA,1).
• Then, (GAT,1), (ATA, 1), (TAG,1), (AGA,1) and these are the only 3 length sequence.

4. c

• After the map function, there is a shuffle function that will shuffle all the keys together and then pass the values to the reduction.
• Shuffle will take the keys and append all the values received from Map function.
• Hence, (AGA,[1,1]) as there are 2 outputs for AGA.
• (GAT,[1]), (ATA,[1]), (TAG,[1]).

5. d

• Reduce function will add all the values that are passed to it keeping the key constant.
• So (AGA,2) and rest all keys have only 1 value. So, it will produce (GAT,1), (ATA,1), (TAG,1).

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