Try this -
%%// Get the cell data into data1
data1 = INPUT_DATA;
%%// Get the data from columns separately
col1 = data1(:,1);
tag_data = vertcat(col1{:});
col2 = data1(:,2);
times_data = vertcat(col2{:});
col3 = data1(:,3);
col3_data = vertcat(col3{:});
%%// Get full data for tag, times and column3
char_array = ['A' 'C' 'G' 'T'];
full_tag_data = char_array(combinator(4,3,'p','r'));
full_tag_data = [full_tag_data(:,1:2) repmat('->',[size(full_tag_data,1) 1]) full_tag_data(:,2:3)];
present_rows = ismember(full_tag_data,tag_data,'rows');
full_times_data = double(present_rows);
full_times_data(present_rows) = times_data;
full_col3_data = double(present_rows);
full_col3_data(present_rows) = col3_data;
%%// Get the sum values
full_col3_data_summed = sum(reshape(full_col3_data,4,[]),1);
full_col3_data_summed = reshape(repmat(full_col3_data_summed,[4 1]),[],1);
%%// Store the required values into a cell array out_cell1
out_cell1 = cell(size(present_rows,1),2);
out_cell1(:,1) = cellstr(full_tag_data);
out_cell1(:,2) = num2cell(full_times_data);
out_cell1(:,3) = num2cell(full_col3_data);
%%// The probabilities are added into the cell array as the fourth column
out_cell1(:,4) = num2cell(full_times_data./full_col3_data_summed);
Note: The above code uses a function combinator
, which is available here.