The most important function of DNA is to carry genes, the information that specifies all the proteins that make up an organism—including information about when, in what types of cells, and in what quantity each protein is to be made.
Bacterial DNA – a circular chromosome plus plasmids. The DNA of most bacteria is contained in a single circular molecule, called the bacterial chromosome. The chromosome, along with several proteins and RNA molecules, forms an irregularly shaped structure called the nucleoid. This sits in the cytoplasm of the bacterial cell The proteins that bind to the DNA to form eucaryotic chromosomes are traditionally divided into two general classes: the histones and the nonhistone chromosomal proteins. The complex of both classes of protein with the nuclear DNA of eucaryotic cells is known as chromatin. Although long strings of nucleosomes form on most chromosomal DNA, chromatin in a living cell probably rarely adopts the extended “beads on a string” form. Instead, the nucleosomes are packed on top of one another, generating regular arrays in which the DNA is even more highly condensed. Chromosomes are made from DNA. Genes are short sections of DNA. Genetically identical cells are produced by a type of cell division called mitosis. In sexual reproduction, a male gamete fuses with a female gamete to produce a new cell. This is called fertilisation. The cell’s nucleus contains chromosomes chromosomes: Rod shaped bodies found in the nucleus of cells that contain genetic information (DNA). made from long DNA molecules. The diagram shows the relationship between the cell, its nucleus, chromosomes in the nucleus, and genes. Nucleus, chromosome and gene. Page: 1  1. 2  2. 3  3. Genes are made of a chemical called DNA, which is short for 'deoxyribonucleic acid'. The DNA molecule is a double helix: that is, two long, thin strands twisted around each other like a spiral staircase. The DNA double helix showing base pairs. The sides are sugar and phosphate molecules. The rungs are pairs of chemicals called 'nitrogenous bases', or 'bases' for short. DNA. deoxyribonucleic acid: an extremely long, double-stranded nucleic acid molecule arranged as a double helix that is the main constituent of the chromosome and that carries the genes as segments along its strands: found chiefly in the chromatin of cells and in many viruses. [1930–35]. (dē′ĕn-ā′). The nucleic acid that is the genetic material determining the makeup of all living cells and many viruses. It consists of two strands of nucleotides linked together in a structure resembling a ladder twisted into a spiral. In eukaryotic cells, the DNA is contained mainly in the nucleus and mitochondria. A chromosome (chromo- + -some) is a packaged and organized structure containing most of the DNA of a living organism. It is not usually found on its own, but rather is complexed with many structural proteins called histones as well as associated transcription (copying of genetic sequences) factors and several other macromolecules. Two sister chromatids (half a chromosome) join together at a protein junction called a centromere. Cell division is a continuous process that must occur for an organism to function, whether for growth, repair or reproduction. During cell division stages, it is the chromosome that is responsible for the replication and distribution of DNA amongst new cells. Strangely enough, the functions of chromosomes in plant cells are the same as the function of chromosomes in animal cells.  When the DNA sequence of human chromosome 22, one of the smallest human chromosomes (see Figure 4-11), was completed in 1999, it became possible for the first time to see exactly how genes are arranged along an entire vertebrate chromosome (Figure 4-15 and Table 4-1). Although long strings of nucleosomes form on most chromosomal DNA, chromatin in a living cell probably rarely adopts the extended “beads on a string” form. Instead, the nucleosomes are packed on top of one another, generating regular arrays in which the DNA is even more highly condensed. Chromosomal DNA and Its Packaging in the Chromatin Fiber. The most important function of DNA is to carry genes, the information that specifies all the proteins that make up an organism—including information about when, in what types of cells, and in what quantity each protein is to be made. Although long strings of nucleosomes form on most chromosomal DNA, chromatin in a living cell probably rarely adopts the extended “beads on a string” form. Instead, the nucleosomes are packed on top of one another, generating regular arrays in which the DNA is even more highly condensed. Compaction of the duplicated chromosomes during cell division (mitosis or meiosis) results either in a four-arm structure (pictured to the right) if the centromere is located in the middle of the chromosome or a two-arm structure if the centromere is located near one of the ends. It is not usually found on its own, but rather is complexed with many structural proteins called histones as well as associated transcription (copying of genetic sequences) factors and several other macromolecules. Two sister chromatids (half a chromosome) join together at a protein junction called a centromere.
http://biotechlearn.org.nz/themes/bacteria_in_biotech/bacterial_dna_the_role_of_plasmids http://www.ncbi.nlm.nih.gov/books/NBK26834/ http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa_pre_2011/celldivision/celldivision1.shtml http://www2.le.ac.uk/departments/genetics/vgec/highereducation/topics/dnageneschromosomes http://www.thefreedictionary.com/chromosomal+DNA https://en.wikipedia.org/wiki/Chromosome http://www.academia.edu/7969110/Structure_Function_and_Molecular_structure_of_Chromosome http://www.ncbi.nlm.nih.gov/books/NBK26834/ http://www.ncbi.nlm.nih.gov/books/NBK26834/ https://en.wikipedia.org/wiki/Chromosome
function of chromosomal dna