How many strands of DNA do we have?

Question

I used to think that our DNA was one long strand but then I realised that our chromosomes are seperate from each other therefore DNA could not be in one long strand. Can it?

Does each chromosome have one long strand or are there more?

Answer 1

Seven answers and nobody got it right!

DNA is double-stranded. This means that each portion of DNA contains 2 helices facing each other and bound to each other by hydrogen bonds. Each strand is composed of a row of bases (A,T,C,G) bound to a sugar ring (deoxyribose) and to a phosphate (PO4^-2) group. Base+sugar ring + phosphate group form a nucleotide. The 2 strands are said "complementary" because they follow a certain predictable pattern, by which each A (adenine) is facing a T (thymidine) and each G (guanine) is facing a C (cytosine).

Having said that, I think what you are asking is :is DNA a long molecule or is it split into "bits"?
The answer is : in eukaryotic cells, i.e. in cells containing a nucleus, DNA is divided into linear molecules called chromosomes. In particular, human somatic cells contain 46 chromosomes (22 pairs of somatic chromosomes + 2 sex chromosomes), each double stranded. If it is true that chromosomes are only VISIBLE during mitosis, it is also true that they still exist during interphase. Only, they appear like a mass of uncondensed chromatin. What regulates the condensation of chromatin into visible chromosomes is the level of tightness in which these DNA molecules are wrapped around the nuclosomes. Nucleosomes are protein complexes formed by histones (mostly): H2a, H2b, H3 and H4 all wrapped around the H1 core.

During S-phase (which has to occur before mitosis), each chromosome is duplicated. This means that the double-stranded molecules of DNA "open up" and each strand is "copied" to give 2 identical molecules. These molecules take the name of "sister chromatides". They are still indistinguishable at this stage, as they are not condensed yet, but they soon will be as the cell enter prophase - i.e. 1st stage of mitosis, when the nucleus disintegrates and the chromosomes become visible.

Hope it helps clearing the confusion.
If you happen to be in Vienna, there is a meeting going on at the moment called "Molecular Machineries" organized by FEBS and deals with chromosomes, replication, mitotic apparatus, etc.....

Answer 2

Number Of Strands In Dna

Answer 3

2

Answer 4

This Site Might Help You.

RE:
How many strands of DNA do we have?
I used to think that our DNA was one long strand but then I realised that our chromosomes are seperate from each other therefore DNA could not be in one long strand. Can it?

Does each chromosome have one long strand or are there more?

Answer 5

LGE,

Thanks for saving us from this nonsense! The D in DNA stands for deoxyribose - not DI (as in 2). Chromosome ALWAYS exist, if they are broken it can be a very serious problem for the cell. E. coli for example (only 1 chromosome) can only withstand approximately 3 double-strands breaks.

In eukaryotic cells the chromosome condenses (lets not forget about cohesins and condensins LGE). These structures are highly visible under light microscopy, and were used back in the old days for karyotyping.

DNA as a very dynamic molecule. It exists primarily as a double-stranded helix, but is single stranded at the replication fork, at sites of DNA damage and repair intermediates as well as at the site of transcription.

It is of great significance that the human genome is split up into many chromosomes with linear DNA molecules. I'll let you ask why another time if you feel like it.

Answer 6

12

Answer 7

LGE, is your answer.

The only thing I add to that, is this is the makeup of EACH and every CELL, or er, at least the ones with nuclei anyway. There are billions of cells in your body, so that tells you that 46 times billions is the number of "strands".

Answer 8

DNA is not usually in the form of chromosomes. Most of the time, it is in the form of chromatin, which is unraveled, and can be in one very long strand. (The unraveled structure makes it much easier for copying enzymes to reach each gene when it needs to.)

Your DNA only bunches up into these compact chromosomes during cellular division. Concerning the 46 chromosomes though, within each chromosome, it is, literally, in one long strand.

The DNA strand itself never "breaks", but rather "unzips" to be read by a copying enzyme, and then only at the gene(s) needing to be copied for protein synthesis at the moment. Once that is done, both sides of the DNA strand "zip" back together.

Even in replication, (making new DNA strands) the DNA strand does not break into smaller sections to be copied. It just unzips.
Imagine yarn. It is made of continuous strands, right? Well, if you unwind the strand-lets from each other, without cutting the yarn, you'll have an idea of how DNA unzips.

Answer 9

32 strands of dna the human body holds.

Answer 10

1 DNA molecule carries 2 stands of bases.
1 chromatid contains 1 DNA molecule.
1 cell contains 46 chromatids

if u calculate it then a cell contains 2*46=92 strands.

CHROMATID is a DNA molecule rapped upon a protien called histone protien. while CHROMOSOMES are 2 chromatids which can only be seen during cell replication, although some books call a single chromatid as a chromosome. It will be beneficial if you concentrate on the question asked to you to see if cell is replicating or no.

NOTICE: strands are not of same length or sizes if chromosomes are different. only homologus (like) chromosomes are equal in length.