What is the difference between a single chromosome and a double chromosome?
462694
Single (haploid) chromosome are those found in gametes (sperm, ova) double chromosomes are those found in somatic cell, the ones that make our whole body.
705722
In every cell of the human body there are 46 chromosomes: 44 somatic coding chromosomes (body coding) and 2 sex chromosomes.\n\nEach chromosome is part of a pair.  Each one of the pair codes for the same thing, though not necessarily the identical way (for example, one of the set may code for blue eyes, one may code for brown eyes). \n\nThe idea of homologous pairs is important during meiosis, when the chromosomes replicate, and find their homologous pairing, forming a tetrad (a structure with 4 chromatids from the joining of 2 replicated homologous chromosomes).\n\nHope this helps.
742169
one chromosome comes from each parent
382853
Chromatids or sister chromatids.
856076
DNA is a double helix while mRNA is a single stranded molecule.
208675
We normally have 23 pairs of chromosomes, that is, 46 chromosomes in total. When they're seen inside of a cell nucleus, they just look like similar V , X and Y shaped little dark spots, but the specialists are able to order them and know which ones belong to each pair (i.e. are homologous). They've labeled the pairs from 1 to 23 (the 23rd pair is the XX or XY sex chromosomes). \nIn Down syndrome, there is an extra chromosome. If you just looked at an image of the nucleus, you'd just count 47 chromosomes. But it has been determined that the "extra" one is a duplicate of one of the members of pair 21. \nIn the case of other duplicate chromosomes, the effects are not Down syndrome. Most cases of chromosomal duplication are lethal.
946006
They are different, one is general and the other is connected to the reproductive details in the DNA as per the explanation given by all the three preceding answerers. All of them are right in their own way so far as the scientific findings on the subject is concerned.
196196
Well, as you may already know, the purpose of both mitosis and meiosis is to take one cell and make two cells. Before the cells do this though, they have to make sure that a few things are in order. Obviously, there has to be enough stuff for the 2 cells to each be able to live independently. so, there has to be duplication of a lot of stuff before the first cell (let's call it the parent) divides. One of these things is the genome. These are the chromosomes which are made up of DNA. Once the DNA replicates (makes 2 copies of everything from what the parent originally had), the cell can divide. There are now 4 chromosomes of each type, we started out with our usual 2 of each (most organisms have 2 of each chromosome and they differ slightly from each other-this becomes important for meiosis), then when everything duplicated, we got 4! \n\nIn MITOSIS, the 2 cells that come out of the division (lets call them the daughters), are EXACTLY the same in genetic makeup as the original mother cell. They have the very same DNA and therefore make the same proteins and therefore the cells behave the same. \n\n In MEIOSIS on the other hand, the cells are not the same at all. And in fact, this is the point of meiosis - to make new types of cells. You may know that eggs and sperm are products of meiosis, but you not only get a mixing of genes from your mother (from the egg) and father (from the sperm), but the genes inside the egg and sperm are pre-mixed because of meiosis. Thus, genetic diversity!, and an explanation for why you have traits given to you from your grandmother through your father, even though your father may not have that trait (he carries it in his genes for later mixing). This may be a complicated issue in itself but since we have 2 of every chromosome and therefore 2 of every gene (even before the DNA replication that preceeds mitosis), there's a chance that the 2 copies of the same gene are different, one of which shows up in your father and one which you have that you got from your grandmother throuh your father. The mixing, by the way comes about because after the DNA replicates in preparation for cell division. This is neat and involves chromosomes breaking apart and joining back together. Take a look at the animated movie of meiosis at http://www.biology.yale.edu/animatedMeiosis.nclk - make a point to notice the red and green chromosomes at the beginning and the mixed ones at the end.
957172
If you are talking about Somatic division (mitosis) , just before division the mother cell will  have 23x2 chromosome pairs that is 23x2x4 chromatids in all. The daughter cells get 23x2x2 chromatids=23 pairs of chromosomes each. In case of meiosis, one more division leads to 23 singlet chromosomes (=23x2 chromatids) each in a daughter cell.
885418
D is definitely the false answer because, in Meiosis I, the homologous chromosomes are seperated. The chromosomes are divided in Meiosis II. The seperating of the two homologous chromosomes into different daughter cells cause the number of chromosomes to be halved.\n\nE is definitely correct because the daughter cells are different from each other due to cross-over and also because of the seperation of homologous chromosomes.
716212
normal cell has 23 pairs of chromosomes (46 chromatids)\nbefore mitotic division the number doubles to 46 pairs (92 chromatids) the chromosomes are arranged as sister chromatids joined by the centromere and aligned with their copies (this is where recombination events can take place). the pairs are then pulled apart and separated in to the two new cells (each with 23 pairs). \n\nNote: for meiotic division (production of gametes (sperm and egg)) 23 pairs of chromosomes are divided in to 2 lots of 23 single chromosomes.
252661
If it is a diploid (2n) and has 30 chromosomes, then it has 30 chromosoms obviously but one usually addresses these as 15 pairs and not 30 chromosomes. The haploid of this would thus be 15 single chromosomes.
839769
Meiosis is specialized cell division (similar to mitosis). Mitosis results in 2 identical daughter cells from a single cell. Meiosis results in 4 daughter cells (which may not be identical) but each daughter cell only has one set of chromosomes, instead of the 2 sets of chromosomes present in the original cell. Each of these daughter cells is called a gamete. In sexual reproduction a male gamete and a female gamete (sperm and egg) fuse. Each contributes a single set of chromosomes so the resulting fused cell (zygote) has two sets like the cells that originally formed the gametes.
393544
two cell divisions.... one for meiosis 1 and one for meiosis 2
815639
DNA is in chromosomes. Chromosomes are in 23 pairs: 2 *different* copies of Chromosome 1, 2 different copies of C2, etc, in each person.  Whether you get your father's Chromosome 1 that he got from his mother, or the one he got from his father, is random with respect to which Chromosome 2 you get from your father. Same goes for your siblings. The chances of two nontwin siblings getting the same exact set of 23 5chromosomes from one parent are vanishingly small. The chances of siblings getting the same exact set of 23 chromosomes from EACH parent are .. well, it's essentially impossible. \n\nSame goes for the possibility that they would receive NO chromosomes in common - although it is theoretically possible to have siblings that share no genetic relation at all.\n\nDNA evidence is never 100% conclusive, but the tests that are widely used (if done properly) have such a small possibility of being wrong that they might as well be 100% conclusive. That's because there's just so much genetic material in any one person, it averages out ... makes it so that siblings are actually very close to 50% alike - even though they could be anywhere from 0 to 0% alike, in theory.
108939
One of the most obvious differences between the DNA of different species is the number of chromosomes.  If you have intact cells, you can do a DNA smash and stain and see how many chromosomes there are - for example dogs have 78 chromosomes, while humans have only 46.   Molecularly, there is no difference, besides a few genes which differ in sequence.
1065164
The cells from two separate eggs (twins) can combine into one whilst in the mother's womb - thus one child is born but has two dna's instead of one