information in the genes of the DNA happens by transcribing the coordinating RNA nucleotide on a base-by-base basis until the entire gene is transcribed with the right mRNA strand. The mRNA that is produced is usually pre-mRNA that needs to undergo a transformation to mature into mRNA that can go to the ribosomes to translate the message into proteins in a process known as translation. This may make a complete protein, a pre-protein that needs modification, or a subunit of a much larger protein complex that needs other subunits to make a complete protein. Alternatively, replication can happen to a sequence of DNA when a cell is about to divide. This results in the copying of an entire chromosome so that it can go into making another cell that has the same set of DNA in the two copied cells. This process requires DNA polymerase and telomerase in order to copy the entire DNA sequence. Genomic DNA is tightly packed in a form called DNA condensation. This allows the chromatin to fit into the very small nucleus inside the cell. Only small amounts of DNA are located outside of the nucleus, such as in the mitochondria in animal cells and chloroplasts in plant cells. The total set of DNA in a cell is called its genotype, while the actual features of the person that occur as a result of the genotype is called the phenotype. This will be discussed further in other chapters of this course. The genes will contain an open reading frame that gets transcribed as well as a regulatory sequence that won’t get transcribed but will be promotor regions or enhancers, which control the rate of transcription of the open reading frame. As mentioned, only a tiny fraction of DNA is actually encoded into a protein. In humans, less than 2 percent actually encodes for a protein. More than half of the DNA involves repetitive segments of non-coding DNA and accounts for the large differences in genome size or C-value. Some non-coding DNA segments will not code for proteins but will code for RNA segments that act to regulate gene expression and are never translated into a protein. In addition, some noncoding DNA segments are important to the structure of the DNA. For example, both telomeres and centromeres are structural parts of the DNA and contain few or no genes but are important to the stability of the chromosome. A lot of noncoding DNA material are called “pseudogenes” because they are actually copies of genes that have been mutated and are therefore disabled. They can further mutate into active genes through divergence and the process of gene duplication.
Transcription, Replication, and Translation As you already know, a gene sequence that contains genetic information can influence a host’s phenotype by making a strand of messenger RNA that ultimately gets translated into a functional protein. The relationship between the bases and the amino acids happens by means of codons, which are three-base-long segments of DNA that code for a specific protein. There is 10
