# Of roaches & radiation

**URL:** <https://boards.straightdope.com/t/of-roaches-radiation/242764>\
**Category:** Factual Questions\
**Created:** [April 29, 2004, 11:51pm UTC](https://boards.straightdope.com/t/of-roaches-radiation/242764 "2004-04-29T23:51:17Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![nevermore](https://avatars.discourse-cdn.com/v4/letter/n/a587f6/32.png) [@nevermore](https://boards.straightdope.com/u/nevermore)\
**Post date:** [April 29, 2004, 11:51pm UTC](https://boards.straightdope.com/t/of-roaches-radiation/242764/1 "2004-04-29T23:51:17Z")

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Alright, a friend of mine claims that cockroach cells divide only once every 7 days, and this is why they’re less susceptible to radiation.

I don’t buy it.

I can believe that each cell is programmed to divide every 7 days. I just can’t see how ALL the cells in a cockroach’s body would divide at once! And I don’t even mean in the same instant in time; that’s just utterly inconceivable-- even within the same 24 or 48 hours, I just don’t see it. It seems to me that at any given time, in any given organism, some proportion of the cells in its body have got to be dividing.

I’m probably wrong, but for the life of me I cannot find a cite that is any more specific than “cockroach cells divide once every 7 days.” Help? Anyone?

Bueller?

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**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\
**Post date:** [April 29, 2004, 11:58pm UTC](https://boards.straightdope.com/t/of-roaches-radiation/242764/2 "2004-04-29T23:58:34Z")

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> [@nevermore](#):
>
> I can believe that each cell is programmed to divide every 7 days. I just can’t see how ALL the cells in a cockroach’s body would divide at once! And I don’t even mean in the same instant in time; that’s just utterly inconceivable-- even within the same 24 or 48 hours, I just don’t see it. It seems to me that at any given time, in any given organism, some proportion of the cells in its body have got to be dividing.

How did you get from ‘each cell divides every 7 days’ to ‘they all do it at once’? I don’t get it.

(I have no idea if the factoid is true, but I still don’t get what you’re saying.

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**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\
**Post date:** [April 30, 2004, 12:04am UTC](https://boards.straightdope.com/t/of-roaches-radiation/242764/3 "2004-04-30T00:04:11Z")

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If they all divide every seven days, but their activity is evenly spread, that means that in any given day, 1/7 (about 14%) of them will have divided; in any given hour 1/168 (just over one half of one percent) of them will have divided.

Seems a little rapid for me, but maybe true for a growing larva.

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**Author:** ![nevermore](https://avatars.discourse-cdn.com/v4/letter/n/a587f6/32.png) [@nevermore](https://boards.straightdope.com/u/nevermore)\
**Post date:** [April 30, 2004, 12:47am UTC](https://boards.straightdope.com/t/of-roaches-radiation/242764/4 "2004-04-30T00:47:41Z")

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> [@Mangetout](#):
>
> How did you get from ‘each cell divides every 7 days’ to ‘they all do it at once’? I don’t get it.

ahhh, sorry-- because [this](http://www.bio.umass.edu/biology/kunkel/cockroach_faq.html#Q5) was the link he was using to try to convince me, which states that “it just so happens that cells are most sensitive to radiation when they are dividing.” He infers from this that “they wouldn’t have major chromosomal damage [from irradiation] unless it was during that one day out of seven.” Hope that makes better sense. 🆒