Is there a way in which the question can be frozen when an answer is being typed for that particular question .Its annoying when the blog say no answers then when you give an answer you suddenly find you have given the same answer as 18 others.If your answer is the same as another one given dont post it as an answer to the question.
There is not a way to do it. It would require software screening answers before they appear, and comparing it with answers already posted.
Such comparison would need intelligent analysis as every answer would have a high number of identical words, even where the answers are very different.