what is the relationship between chromatin and DNA? | Yahoo Answers
Start studying b DNA, Chromatin, and Chromosomes. Describe the structural relationship of DNA and chromatin, and the functional relationship of DNA. The chromosomes are composed of DNA. When cells are not actively dividing the chromosomes appear as a tangled mass (chromatin). Chromatin is a strand of DNA wrapped around a protein, and is a building block of all chromosomes. The chromosome is the structure in which DNA is stored in.
Sinauer Associates ; Search term Chromosomes and Chromatin Not only are the genomes of most eukaryotes much more complex than those of prokaryotes, but the DNA of eukaryotic cells is also organized differently from that of prokaryotic cells. The genomes of prokaryotes are contained in single chromosomeswhich are usually circular DNA molecules.
In contrast, the genomes of eukaryotes are composed of multiple chromosomes, each containing a linear molecule of DNA. Although the numbers and sizes of chromosomes vary considerably between different species Table 4. The DNA of eukaryotic cells is tightly bound to small basic proteins histones that package the DNA in an orderly way in the cell nucleus.
This task is substantial, given the DNA content of most eukaryotes. Although DNA packaging is also a problem in bacteria, the mechanism by which prokaryotic DNAs are packaged in the cell appears distinct from that of eukaryotes and is not well understood. Chromosome Numbers of Eukaryotic Cells.
Chromatin The complexes between eukaryotic DNA and proteins are called chromatinwhich typically contains about twice as much protein as DNA.
The major proteins of chromatin are the histones —small proteins containing a high proportion of basic amino acids arginine and lysine that facilitate binding to the negatively charged DNA molecule. The histones are extremely abundant proteins in eukaryotic cells ; together, their mass is approximately equal to that of the cell's DNA.
In addition, chromatin contains an approximately equal mass of a wide variety of nonhistone chromosomal proteins. There are more than a thousand different types of these proteins, which are involved in a range of activities, including DNA replication and gene expression.
Histones are not found in eubacteria e.
What is the relationship between chromatin and DNA?
Archaebacteria, however, do contain histones that package their DNAs in structures similar to eukaryotic chromatin. The basic structural unit of chromatinthe nucleosomewas described by Roger Kornberg in Figure 4.
Two types of experiments led to Kornberg's proposal of the nucleosome model. First, partial digestion of chromatin with micrococcal nuclease an enzyme that degrades DNA was found to yield DNA fragments approximately base pairs long. In contrast, a similar digestion of naked DNA not associated with proteins yielded a continuous smear of randomly sized fragments.
How can the relationship between DNA and the chromatin be described? - Quora
These results suggested that the binding of proteins to DNA in chromatin protects regions of the DNA from nuclease digestion, so that the enzyme can attack DNA only at sites separated by approximately base pairs. Consistent with this notion, electron microscopy revealed that chromatin fibers have a beaded appearance, with the beads spaced at intervals of approximately base pairs.
Thus, both the nuclease digestion and the electron microscopic studies suggested that chromatin is composed of repeating base-pair units, which were called nucleosomes. Nonhistone proteins bind to the linker DNA between nucleosome core particles. B Gel electrophoresis of DNA fragments more More extensive digestion of chromatin with micrococcal nuclease was found to yield particles called nucleosome core particles that correspond to the beads visible by electron microscopy.
Detailed analysis of these particles has shown that they contain base pairs of DNA wrapped 1. The lack of compaction of these regiongs is called bookmarking, which is an epigenetic mechanism believed to be important for transmitting to daughter cells the "memory" of which genes were active prior to entry into mitosis.
This bookmarking mechanism is needed to help transmit this memory because transcription ceases during mitosis Deoxyribonucleic acid DNA is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms and some viruses. The main role of DNA molecules is the long-term storage of information.
DNA is often compared to a set of blueprints or a recipe, since it contains the instructions needed to construct other components of cells, such as proteins and RNA molecules. The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in regulating the use of this genetic information.
Chemically, DNA is a long polymer of simple units called nucleotides, with a backbone made of sugars and phosphate groups joined by ester bonds. Attached to each sugar is one of four types of molecules called bases.
It is the sequence of these four bases along the backbone that encodes information. This information is read using the genetic code, which specifies the sequence of the amino acids within proteins.
What is the relationship of DNA, a chromosome, and chromatin?
Within cells, DNA is organized into structures called chromosomes. These chromosomes are duplicated before cells divide, in a process called DNA replication. Eukaryotic organisms animals, plants, and fungi store their DNA inside the cell nucleus, while in prokaryotes bacteria and archae it is found in the cell's cytoplasm.
Within the chromosomes, chromatin proteins such as histones compact and organize DNA. These compact structures guide the interactions between DNA and other proteins, helping control which parts of the DNA are transcribed.