Is it possible to sort out similar rows in a table and put the number in a column? I have this table
gene  5   5  5
gene  4   4  3
gene  5   5  5
gene  1   4  5

and I would like to have the following,
gene  5   5  5   2
gene  4   4  3   1
gene  1   4  5   1

so in the last column I would have a number of similar rows (in this case it's gene 5 5 5, that is present two times in the original table, while others presented only once).
What would be the best approach to do it? Is it a job for awk? Actually, is it even possible in Linux?

$ sort data.txt|uniq -c|sed -e 's/[ ]*\([0-9]\)   \(.*\)$/\2 \1/'|sort -nrk 5
gene  5   5  5   2
gene  4   4  3   1
gene  1   4  5   1