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<> Biomolecules Nucleic Acids. There are two nucleic acids RNA: Ribonucleic Acid DNA: Deoxyribonucleic Acid The composition and Structure of DNA and RNA DNA and RNA are polymers of monomers called nucleotides. A nucleotide consists of three distinct parts: ¾A 5 carbon (pentose) sugar ¾A phosphate group PO4-3 ¾A nitrogen base The pentose sugar Pentose = C5 Each carbon is numbered clockwise beginning at 12:00. Only four carbons are used in the cycle which is enclosed with an -O-. The fifth carbon is part of the cycle. The Phosphate Group The phosphate forms a bond with the pentose’s carbon # 3. It has negative charge, thus all the nucleic acid molecule will be negatively charged. The nitrogen bases The are four nitrogen bases Adenine or A, Guanine or G. These are call purines and they have a double cycle. Cytosine C, Thymine, T and Uracil are called pyrimidines and they have a single cycle. RNA Ribonucleic Acid The 5 C sugar is = RIBOSE The nitrogen bases are: A, C, G and U, never T RNA is a single strand There are 3 types of RNA. mRNA: messenger RNA tRNA : transfer RNA rRNA: ribosomal RNA Function of RNA: All RNA is involved in protein synthesis (manufacturing) DNA Deoxyribonucleic Acid The 5 C sugar is = DEOXYRIBOSE The nitrogen bases are: A, C, G and T, never U DNA is a double strand The addition of multiple nucleotides using deshydration synthesis lead to the formation of a large chain. Notice that the last nucleotide (C3) does not have a phosphate group, thus this strand of DNA “runs” from a 5’ 3’ and it is known as the “sense” strand. The Chargaff Rule 1948 Edwin Chargaff hydrolized DNA from different organisms and demonstrated that the composition of double stranded DNA was 50% purine and 50% pyrimidine. A+G ==1 1 C+T Furthermore, he demonstrated that the amount of Adenine was very similar to the amount of Thymine and the amount of Guanine was similar to the amount of Cytosine. These equivalencies are known as Chargaff rules. Watson and Crick discovered the double helix by building models to conform to Xray data By the beginnings of the 1950’s, the race was on to move from the structure of a single DNA strand to the three-dimensional structure of DNA. Among the scientists working on the problem were Linus Pauling, in California, and Maurice Wilkins and Rosalind Franklin, in London. Maurice Wilkins and Rosalind Franklin used X-ray crystallography to study the structure of DNA. The Watson and Crick Model Watson and Crick used the data produced by Wilkins and Franklin to produce a three dimensional model of the structure of DNA. The second strand The second strand of DNA follows the same principles that we have studied so far. It is positioned “upside down” and it is a mirror image of the first strand (a 180 degree vertical rotation). However, if this was a “true” mirror image, the nitrogen bases should be the same and that is not the case: The nitrogen bases are complementary. Complementary bases mean, that if in the first strand we find a purine base, in the second strand we will find a pyrimidine and viceversa. Complementary bases First strand (sense) Second strand (antisense) The two strands are linked together by hydrogen bonds. Once the two strands are bond together, the entire structure twists to the right (right handed or clock wise) to form a helical structure known as a “double helix”. And the rest is History! Some DNA information Cellular DNA is organized into chromosomes. The genome is all the genetic information (all the genes) of one organism. A gene is a fragment of DNA that has the information for one specific trait. Examples: color of the eyes. All the variations of one gene are called alleles: for example, blue, green, almond, brown, red, etc. What is the name of the movie? What did the teacher tell his students?