MEIOSIS QUESTIONS ON DNA... HELP!!!

NewtoBiology · Post by **NewtoBiology** » Tue Jan 08, 2008 3:56 am

MEIOSIS QUESTIONS ON DNA... HELP!!!

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Post by NewtoBiology » Tue Jan 08, 2008 3:56 am

Hello all Biologists!

I am REALLY REALLY new to biology and I would so appreciate if ANYONE could help clear the air for me.

I am currently studying about meiosis and need some help....

Q: For a cell that is 2n=8 answer the following:

1. how many molecules of DNA are in the cell at prophase I.
I AM SO SORRY FOR MY MISUNDERSTANDING OF THIS SEEMINGLY TRIVIAL QUESTION BUT IS IT TRUE TO SAY THEN..... because the chromosomes are duplicating they resemble X's..... so does that mean in a cell at prophase I (with 8 chromosomes present) there would be 16 molecules of DNA??? One molecule per chromatid??!?!?!?? So in a duplicating chromosome there would be 2 molecules of DNA????

OH please dear Biologists help me.

:-)

NewtoBiology!!!

mith · Post by **mith** » Tue Jan 08, 2008 4:57 am

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Post by mith » Tue Jan 08, 2008 4:57 am

DNA is not a molecule, perhaps the word you're looking for is chromosome.

Living one day at a time;
Enjoying one moment at a time;
Accepting hardships as the pathway to peace;
~Niebuhr

MichaelXY · Post by **MichaelXY** » Tue Jan 08, 2008 6:31 am

Re: MEIOSIS QUESTIONS ON DNA... HELP!!!

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Post by MichaelXY » Tue Jan 08, 2008 6:31 am

http://www.accessexcellence.org/RC/VL/GG/meiosis.html

MrMistery · Post by **MrMistery** » Tue Jan 08, 2008 11:40 am

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Post by MrMistery » Tue Jan 08, 2008 11:40 am

you are correct Newtobiology. the answer is 16.
Though DNA is not a molecule, as one DNA molecule is actually two molecules(hydrogen bonds are intermolecular) the answer you are supposed to give is probably 16.

"As a biologist, I firmly believe that when you're dead, you're dead. Except for what you live behind in history. That's the only afterlife" - J. Craig Venter

NewtoBiology · Post by **NewtoBiology** » Tue Jan 08, 2008 12:41 pm

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Post by NewtoBiology » Tue Jan 08, 2008 12:41 pm

Thank you everyone!

So just so that I 100% understand. Each chromosome has a DNA strand wound up in it? Therefore non-duplicating Chromosomes, that look like single fingers, contain one strand of DNA. Is this correct?

Therefore in duplicating Chromosomes, that look like X's, there are two strands of DNA (double helix strand). Is this correct?

canalon · Post by **canalon** » Tue Jan 08, 2008 1:58 pm

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Post by canalon » Tue Jan 08, 2008 1:58 pm

NewtoBiology wrote:Thank you everyone!

So just so that I 100% understand. Each chromosome has a DNA strand wound up in it? Therefore non-duplicating Chromosomes, that look like single fingers, contain one strand of DNA. Is this correct?

Therefore in duplicating Chromosomes, that look like X's, there are two strands of DNA (double helix strand). Is this correct?

Each chromosome is made of 2 DNA molecules wound up in a double helix, the double helix looks like the "single finger". In the duplicating chromosome the 2 strands are separated (but stay attached in the middle), and each single strand of the double helix is completed (by base complementation) to form a new double helix. So you X shaped chromosome is made of 4 DNA strands, and each half is made of 1 "old" DNA strand and 1"new" complementary DNA strand.

Patrick

Science has proof without any certainty. Creationists have certainty without
any proof. (Ashley Montague)

mith · Post by **mith** » Tue Jan 08, 2008 2:33 pm

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Post by mith » Tue Jan 08, 2008 2:33 pm

It's probably helpful to review the terms chromosomes, chromatids, sister chromatids etc.

Living one day at a time;
Enjoying one moment at a time;
Accepting hardships as the pathway to peace;
~Niebuhr