Question from Khan Academy Bio Passage: Mechanisms of antibody variability during B-cell development

[Phantom1412]

Im having some difficulties understanding how to arrive at the proposed answer.

Question: Suppose the last six nucleotides of a Dh gene segment are 5’-GTCGAT-3’. A P-addition was made, forming a palindromic sequence on the 3’ end. If the original double-stranded DNA was cleaved three nucleotides from the 5’ end, what sequence of complementary nucleotides would repair enzymes add to the resulting open strand?

The initial dsDNA will be cut like this:

5'-GTC || GAT-3'
3'-CAG || CTA-5'

Now, according to the diagram, P-addition produces the follow result:

5'-GTCGAC-3' 5'-ATCGAT-3'
3'-CAGCTG-5' 3-TAGCTA-5'

How did they arrive at the answer 5'-GATATC-3'? Can someone tell me where my understanding falters?

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[wizzed101]

5'-GTC GAT -3'
3'-CAG CTA- 5'

after cleavage

5'-GAT-3'
3'-CTA-5'

P-addition

5'-GAT ATC-3'
3'-

Repair
5'-GAT ATC-3'
3'-CTA TAG-5'

 

[Phantom1412]

5'-GTC GAT -3'
3'-CAG CTA- 5'

after cleavage

5'-GAT-3'
3'-CTA-5'

P-addition
5'-GAT ATC-3'
3'-

Repair
5'-GAT ATC-3'
3'-CTA TAG-5'

This is exactly what I needed. Thanks for the insight!