Hon. Biology Period 6

Nucleic Acids Nucleic acids are large complex organic molecules composed of carbon, oxygen, hydrogen, nitrogen, and phosphorus atoms. Nucleic acids are polymers of individual monomers known as nucleotides. There are two basic kinds of nucleic acids: ribonucleic acids (RNA) and deoxyribonucleic acids (DNA). RNA and DNA both go through transcription. Single- stranded vs. double- stranded.

The Structure of DNA DNA contains four nitrogenous bases: -Adenine -Guanine -Thymine -Cytosine Individual nucleotides are joined together to form a long chain.

In the early 1950s, Rosalind Franklin began to test X-ray beams with DNA. The X-ray scattering produces a pattern that provides important clues to the structure of many molecules. The Structure of DNA This X-ray diffraction photograph of DNA was taken by Franklin. The X- shaped pattern in the center indicates that the structure of DNA is helical.

The Structure of DNA At the same time that Franklin was doing her work, two English scientists were also determined to find the structure of DNA. Francis Crick and James Watson built 3-D models of DNA. Watson observed Franklin’s X-ray pattern of DNA and thus realized the importance of it. Through base pairing, they soon realized DNA’s structure was a double helix. The structure of the DNA double helix resembles a twisted ladder. Sugar-phosphate and nitrogenous bases form the ladder.

The Structure of RNA There are 3 major differences between RNA and DNA. The sugar in RNA is ribose, not deoxyribose. RNA consists of a single strand of nucleotides, and DNA is double-stranded. The nitrogenous bases in RNA are different than DNA. RNA contains: Adenine Cytosine Guanine Uracil

Replication Before a cell divides, it must duplicate its DNA. This copying process is called REPLICATION. It is carried out by a series of enzymes. These enzymes “unzip” the double-helix, insert the bases, and create links to extend the chain. When DNA undergoes replication, each of the original strands serves as a template along which a new strand forms.

Transcription Transcription is the process by which a molecule of DNA is copied into a complementary strand of RNA. In other words, it is the process of transferring information from DNA to RNA.

Translation What's Involved in Translation? mRNA - the template with instructions for the order of amino acids in the polypeptide (protein) chain. tRNA - molecules that transport amino acids to site of translation (the ribosome). ribosomes - serves as the site of translation and regulates the tRNA molecule's joining with the mRNA.