user19468: I just found this question. I believe this question to be off-topic, because it is really a statistics question, belonging to Cross Validated. However I couldn't select Cross Validated in the list of possible options, I could only select 'biology.meta.stackexchange.com'. 
On Stack Overflow, I remember to be able to select a whole lot of options. Why not here?
Not sure if this is a feature-request or a bug, so tagging both.

user9943: General answer on flagging for off-topic
The off topic reasons are limited to Chemistry. Perhaps because of a long gone meta post or something, who knows. One way or another, if you wish to close vote because it should go to Health, CogSci, or what have you, please consider making a custom-made close vote using 'Off topic, because' -
-- 'Other' and write a customary reason. 
If you do this, please advise on migration only for top-notch questions. I see quite a lot of below-average questions getting redirected to CogSci, which is not beneficial to a fragile beta site like that. 
Specific answer for off-topicness of statistics questions
The linked question is a question on the statistics behind Mendelian genetics. That is statistics, yes, but applied to a classical field of Biology and hence a subject fitting perfectly on our site in my opinion. Also see the post here on closing supposedly borderline questions that received a valid answer within this site's conventions.

19468: <p>I just found <a href="https://biology.stackexchange.com/questions/57997/does-one-need-to-perform-two-chi-square-tests">this</a> question. I believe this question to be off-topic, because it is really a statistics question, belonging to Cross Validated. However I couldn't select Cross Validated in the list of possible options, I could only select 'biology.meta.stackexchange.com'. </p>

<p>On Stack Overflow, I remember to be able to select a whole lot of options. Why not here?</p>

<p>Not sure if this is a feature-request or a bug, so tagging both.</p>
 9943: <p><strong>General answer on flagging for off-topic</strong><br>
The off topic reasons are limited to Chemistry. Perhaps because of a long gone meta post or something, who knows. One way or another, if you wish to close vote because it should go to Health, CogSci, or what have you, please consider making a custom-made close vote using 'Off topic, because' -
-- 'Other' and write a customary reason. </p>

<p>If you do this, please advise on migration only for top-notch questions. I see quite a lot of below-average questions getting redirected to CogSci, which is not beneficial to a fragile beta site like that. </p>

<p><strong>Specific answer for off-topicness of statistics questions</strong><br>
The <a href="https://biology.stackexchange.com/questions/57997/does-one-need-to-perform-two-chi-square-tests">linked question</a> is a question on the statistics behind <em>Mendelian genetics</em>. That is statistics, yes, but applied to a classical field of Biology and hence a subject fitting perfectly on our site in my opinion. Also see <a href="https://biology.meta.stackexchange.com/questions/3576/whats-the-point-of-closing-well-answered-and-well-received-questions/3577#3577">the post here on closing supposedly borderline questions that received a valid answer within this site's conventions.</a></p>
