Chromosomes are the basic units of genetic material in all living organisms. They contain DNA or genetic material which is transcribed into RNA (ribonucleic acid) and then translated into proteins by the ribosome. There are two types of chromatin: nuclear and cytoplasmic. Nuclear chromatin is found within cells, while cytoplasmic chromatin is found outside of cells. Prokaryotic cells can be referred to as “bacteria” and eukaryotic cells as “animals, plants, fungi, and protists”.
Nuclear and cytoplasmic chromatin can be found in both prokaryotes and eukaryotes. Prokaryotic cells, or “bacteria” are the smallest and simplest forms of life and contain only one prokaryotic chromosome. Eukaryotic cells can be referred to as “animals, plants, fungi, and protists” and contain multiple chromosomes.
The difference between nuclear and cytoplasmic chromatin is that nuclear contains the genetic material and is found within the cell while cytoplasmic is outside of the cell and contains little genetic material.
Nuclear and cytoplasmic chromatin came about through natural selection. The structure of the chromosome was so that the genetic material wouldn’t be destroyed by cellular activity as it continued to develop.
The word “chromosome” is coined by German biologist Theodor Boveri in 1903 from the Greek root words “chroma”, meaning “color” and “soma”, meaning “body”.
Prokaryotic cells only contain one chromosome made up of DNA and proteins surrounded by a membrane. Eukaryotic cells, or “animal, plant, fungi, and protist” cells contain multiple chromosomes, which evolved for increased specialization. Prokaryotic cells have less DNA than eukaryotes, making up only 1 or 2 percent of the cell, while eukaryotes have more due to their larger size.
The picture depicts how DNA found in the chromosomes is replicated, transcribed, and translated through the cell during cell division. The DNA is replicated to produce two identical copies, the RNA is transcribed into a single strand of mRNA, and finally this mRNA is translated into amino acids that form proteins.
Through the process of natural selection, eukaryotic cells have evolved to contain more than one prokaryotic chromosome. This occurred through the prokaryotic cells engulfing other smaller prokaryotes. The smaller prokaryotic cells became parasites, evolving to provide benefits to the larger cell in exchange for nutrients.
While prokaryotes only contain one chromosome, eukaryotes contain multiple chromosomes.
This is the basic difference between a prokaryote and a eukaryote.
The structure of a prokaryote’s chromosome is very basic. It is composed of a single DNA molecule and a nucleoid, which is composed of proteins and RNA. The DNA molecule contains genes, regulatory sequences, and regions between genes known as introns. The genes that are actively being used in the cell are transcribed into RNA and the introns are spliced out.
The resulting mRNA is then used to produce proteins.
Eukaryotic cells contain multiple chromosomes in the nuclei of their cells. Dividing this chromosomal DNA into distinct chromatids occurs during the process of cell division. Prokaryotes do not have these structures, and their DNA is found in a single, linear chromosome.
The figure to the left shows a comparison of the chromosomal structures of a typical human cell and prokaryote cell. The human chromosome is on the left, and the prokaryote chromosome is on the right. The arrows pointing to the arrows show the direction in which each strand of DNA is read. Notice that both strands in the prokaryote are read in the same direction, while the human chromosome has one strand read in one direction and the other in the other.
Chromosomes are located in the nucleus of a cell. They contain the majority of genetic information in the cell and are organized into genes, which are then organized into operons.
The genes contain all of the information needed to create specific proteins that are then used by cells to perform specific functions. They are made up of exons, which contain the actual coding information for proteins, and introns, which do not code for anything but need to be present in order for the exons to be spliced together correctly during the mRNA processing stage.
Chromosomes in eukaryotes are stored in the cell’s nucleus and are separate structures within the membrane. Each chromosome is stored as a single thread, which is coiled up when not in use. When the cell requires the use of certain genes from a chromosome, the thread will unravel and the chromosome will be used in DNA replication and RNA transcription.
Eukaryotes have a single thread for each of their chromosomes, while prokaryotes have a single, long thread that contains all of the genetic information.
The genetic information in eukaryotes and prokaryotes is read in a different way. In eukaryotes, the information is read in a segmental manner, with each section being read, then moved along to the next to create one long chain of information. Prokaryotes read their genetic information as a single, continuous strand.
The main difference between prokaryotes and eukaryotes is that prokaryotes are simpler in their structure. They don’t have as much internal structure as eukaryotes do.
There are two types of prokaryotes: Bacteria and Archaea.
Bacteria are prokaryotes that lack a true nucleus and other organelles. The DNA in a bacterial cell is found in a region known as the nucleoid. The cell’s DNA is a single, long thread that coils up to fit inside the cell.
Bacterial cells are typically small, and they don’t have a membrane bound nucleus. They do, however, have a rigid cell wall that protects the rest of the cell.
Bacterial cell reproduction is known as binary fission. This simply means that the cell replicates, then splits into two identical daughter cells. The process of binary fission is shown below.
Archaea are prokaryotes that can be considered “evolved bacteria”. They are similar to bacteria in that they lack a nucleus and other organelles. The DNA of an Archaean cell is located in a region known as the nucleoid. The major difference between Archaea and Bacteria is that many Archaea have internal membranes like eukaryotes.
Archaea can be either motile or non-motile. Motile Archaea move using flagella, while non-motile Archaea use pressures to push them along.
Archaea reproduce through a process known as binary fission just like bacteria. They are also typically small, with cell walls for protection.
The genetic difference between Archaea and Bacteria is very small. Some scientist believe that the two groups should be classified together as prokaryotes. Other scientist believe that their genetic differences are large enough to merit separate categories.
For your purposes, it doesn’t matter. Both prokaryotes and eukaryotes have a nucleus. That is what you will be concerned with.
The nucleus houses two different types of DNA: mitochondrial and nuclear.
Mitochondrial DNA differs from nuclear DNA in that it has a small thread, and most of it is circular. This means that it has two “ends”, and one end is stuck inside the cell, while the “open” end sticks out of the nucleus. The mitochondrial DNA contains information on creating molecules that create energy for the cell.
Nuclear DNA is found in the nucleus, and it contains all of the important information that keeps the cell alive. The nucleus is protected by a membrane that prevents the DNA from being affected by external sources.
The process of cell division is different for prokaryotes and eukaryotes.
Prokaryote cell division, known as binary fission, is a simple process.
The DNA is replicated, and the cell splits in half along its equator. The two identical daughter cells are then free to move off and follow their own paths.
Eukaryote cell division is more complicated, and it involves several stages.
The DNA is replicated, and the nucleus of the cell divides. The rest of the cell does not divide; instead, it becomes semispherical as the cytoplasm moves inward. After the nucleus has undergone division, the cytoplasm reforms into a more spherical shape. The membrane of the cell then pinches inward to form a “slit” between the inner and outer membranes.
The inner membrane contains all of the organelles, and it is pinched off from the outer membrane. This forms a double membrane-bound cell, called a ” cytokine “. The cytokine then undergoes internal division to form two separate cells.
The cytokine is important when considering what factors affect the growth of cells. Since the cytokine is the stage between a single celled organism and a multicellular organism, it is the link between the two. It is therefore subject to the pressures of natural selection. Factors that affect cytokines will therefore indirectly affect the multicellular forms as well.
Organelles are the structures within a cell that have a specialized function. For example, ribosomes are responsible for creating proteins from amino acid sequences.
The organelles that are in the cell’s cytoplasm are known as “free” organelles. They can move about independently within the cytoplasm.
The organelles that are trapped inside the cell’s membrane are known as “membrane-bound”. They cannot move about freely; they are fixed in one place, and their functions are dependent upon where they are localized within the cell.
Many eukaryotes have a structure known as a “chloroplast” or “chlorophyllous organelle”. This structure lies within the cytoplasm and is bound by a membrane. It contains the green pigment chlorophyll; hence, the name. The chloroplast is an example of a membrane-bound organelle.
Chloroplasts are very important in the process of cellular respiration. This process is the method by which a cell obtains energy. In this process, the chloroplast traps light from the sun and uses it to create sugars. These sugars are then released into the cytoplasm for energy.
The chloroplast is not the only membrane-bound organelle. There are others, each with unique functions.
Ingredients for life are simply materials that can be found in the environment. For life to exist, an organism must have a source of both energy and matter. Energy is provided in the form of sunlight or chemical energy (such as is found in glucose).
Life must also obtain an source of matter. For the purposes of this paper, “matter” refers specifically to carbon. If an organism has an source of energy but no source of carbon, it will die. If an organism has an source of carbon but no source of energy, it will also die.
Both energy and matter are vital for life to exist.
One other vital ingredient for life is water. Water can be found in three states: liquid, solid, and gas (vapor). Water is vital because it can act as a solvent, which means it can dissolve other materials. A good example of a solvent is concrete.
Concrete can be used to hold together gravel, sand, water, and cement. Solvents are also able to dissolve certain materials; for instance, water can dissolve sugar.
Solutions are also able to conduct electricity. If two wires are placed in a bucket of water and a battery is hooked up to the wires, the electrons will move through the wires and into the water. The electrons will then continue on their journey until they run into something that will accept them. This is known as an electric current.
The solution allows the electrons to flow freely.
The “genes” of an organism are snippets of deoxyribonucleic acid, often shortened to “DNA”. DNA has the ability to tell the cell how to react in certain situations. For instance, the DNA of a human being has the genes for eye color, hair color, and other various traits. All of this information is stored in the cell’s nucleus.
The information stored in the DNA can be altered by an external source. This is known as “mutation”. Mutations are changes to the genes that exist within the DNA. If a mutation occurs, the cell may tell itself to create something different than it is supposed to.
This can have both advantageous and disadvantageous effects on the organism.
Other than genes and DNA, there are other hereditary traits that can be passed on to offspring. One of these is the “chromosome”. A chromosome is a structure within the cell (nuclear or otherwise). The chromosome is a thread-like object that exists in the cell.
The thread is coiled up when not in use and is used in the creation of proteins and other structures within the cell.
Other hereditary traits passed on to offspring are organelles such as the mitochondrion. The mitochondrion is an organelle that creates Adenosine triphosphate, or ATP. ATP is vital to life because it contains a lot of energy. ATP exists within the cell and is able to store a large amount of energy within a small space.
ATP causes the “fuel” of life, also known as adenosine di-phosphate, or ADP, to split into two. In doing so, large amounts of energy are released.
As one can see, life as we know it would not exist without the proper combination of chemicals and elements. These chemicals and elements allow for the creation of all the cells that people and animals are made up of. The cells are what make up an organism, and the organism is what comprises life.
Without the right combination of elements and chemicals, life as we know it would not exist.
Sources & references used in this article:
- Characterization of a prokaryotic SMC protein involved in chromosome partitioning (RA Britton, DCH Lin, AD Grossman – Genes & development, 1998 – genesdev.cshlp.org)
- Prokaryotic chromosomes and disease (J Hacker, U Hentschel, U Dobrindt – Science, 2003 – science.sciencemag.org)
- MicroReview: Divided genomes: negotiating the cell cycle in prokaryotes with multiple chromosomes (ES Egan, MA Fogel, MK Waldor – Molecular microbiology, 2005 – Wiley Online Library)
- Chromosome structure (H Ris, DF Kubai – Annual review of genetics, 1970 – annualreviews.org)
- Plasmid and chromosome segregation in prokaryotes (J Møller-Jensen, RB Jensen, K Gerdes – Trends in microbiology, 2000 – Elsevier)