DNA/RNA Essay Sample:
The organic compounds deoxyribonucleic acid (DNA), and ribonucleic acid (RNA) are the basis of hereditary, and can be found in the cells of all prokaryotic and eukaryotic organisms. Both nucleic acids are structured as a strand of repeating units referred to as monomers, or better known as nucleotides.
The nucleotides consist of three components a pentose sugar, a phosphate ester group, and a base. The sugar component of the nucleic acids accounts for one of the main differences between the two. DNA includes the sugar deoxyribose, which has one less oxygen atom than ribose the sugar found in RNA, hence the name deoxy-. The sugar component is then attached to phosphate groups which together make up the backbone of the nucleic acid. The base component attached to the sugar is branched off the nucleotide chain and is composed of either a purine or pyrimidine. The purines are double ringed units called guanine and adenine. The pyrimidines are single ringed units called cytosine, thymine, or uracil. The pyrimidine bases are another difference between RNA and DNA with DNA having the bases cytosine and thymine and RNA having the bases cytosine and uracil; therefore a difference between the uracil and the thymine. The combinations, or sequence of the bases arranged along the nucleic acid strand are unique for every gene and can be thousands of nucleotides long therefore the number of possible combinations is limitless.
Another major difference between DNA and RNA is the difference in their molecular structures. RNA is a single stranded polynucleotide chain, and DNA is double stranded chain. The DNA nucleotide strands wind around each other in what is called a double helix which is held together by hydrogen bonds between the bases. The two strands of the helix are complementary meaning the bases are not aligned identical on each strand but, in a certain pattern. The single ring purine base will only pair with a double ring pyrimidine base which allows for the structure to be helical by having a fixed interchain distance. Another reason for the helical structure is that the molar amounts of the paired bases are equal; therefore guanine will only pair with cytosine, and adenine with thymine.
DNA found in the nuclei of all cells is the physical basis of heredity. DNA is found concentrated in the chromosomes of sexually reproducing organisms. During reproduction the chromosomes of the both parents combine providing each new individual genetic material from each parent.
DNA replication, transcription, and translation allows for transmission of genetic information to new cells. Replication involves the separation of the DNA double helix in which each parent strand serves as a template for nucleotide bases to pair with creating a new complimentary strand. After completion of replication two new double helixes are formed from the original one. Therefore after a cell divides each daughter cell gets a DNA molecule carrying information form the parent cell. The process of transcription in which proteins are synthesized is similar to the replication process. The information in a DNA molecule is copied into a molecule of messenger RNA which can then be carried out of the cell nucleus into other parts of the cell. The information carried in the messenger RNA allows for the production of a specific protein through translation. Translation occurs when messenger RNA is attached to ribosomes in the cell.
During translation the mRNA is read as a sequence of codons which include three bases. Each codon specifies a specific amino acid to be added to a polypeptide chain. An example of the formation of an amino acid is the codon with bases UGG which would produce the amino acid Tryptophan.