Proportion of a gene mutation across different age groups

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Hi everybody!
I am trying to analyze in SPSS if there a significant difference in the proportion of a gene mutation among different age groups (20-29, 30-39, etc).
I codified the age groups from the continuous var (age) into a nominal variable with values 1,2,3,etc for each age group and the gene mutation with 0 for negative and 1 for positive. In total, I have 6990 rows (cases) with valid entries for both age group and gene mutation to be analyzed. Frequency table looks like this:


Which test do you recommend to be used to see if this gene is more or less mutation across the age groups? I have already performed chi-square testing on this whole table and it gives me a very significant value, but how can I know which age groups really different?
Thanks a lot in advance! Luca