Task 1 https://www.youtube.com/watch?v=8kK2zwjRV0M http://www.life10e.com/act04.02.html http://www.nobelprize.org/educational/medicine/dna/ Need to know: 1. Detailed knowledge of the structure of DNA/RNA a. 5’ end, 3’end, parallel, antiparallel, complementary, nucleotides, base pairing, single-stranded, double-stranded, ribonucleotide, deoxyribonucleotide 2. Detailed knowledge of DNA replication 3. DNA polymerase, primers, Okazaki fragment, leading strand, lagging strand, phosphodiester binding, DNA polymorphism 4. Basic understanding of transcription and translation a. significance of the genetic code The Science of Biology: Chapter 4 -Nucleic Acids & The Origin Of Life -What are the Chemical Structures and Functions of Nucleic Acids? 1. Nucleic Acids- are polymers specialized for the storage, transmission, and use of genetic info. There are 2 types of nucleic acids: a. DNA (deoxyribonucleic acid) - a macromolecule that encodes hereditary info and passes it from generation to generation. b. RNA (ribonucleic acid) - an often single-stranded nucleic acid whose nucleotide use ribose rather than deoxyribose and in which the base uracil replaces thymine found in DNA. Serves as genome from some viruses. Nucleotides are the Building Blocks of Nucleic Acids ➔ Nucleic Acids are polymers composed of monomers called nucleotides ◆ Nucleotides consists of three components: a nitrogen-containing base, a pentose sugar, and one to three phosphate groups ↑ (Deoxyribose for DNA and Ribose for RNA) ◆ Nucleosides consists of a pentose sugar and a nitrogenous base, but no phosphate group. ➔ The Bases of Nucleic Acids take one of 2 Chemical Forms ◆ Pyrimidine a six-membered single-ring structure ◆ Purine a fused double-ring structure ➔ The Formation of a Nucleic Acid ◆ Phosphodiester Linkage new nucleotide are added to an existing chain one at a time. The pentose sugar in the last nucleotide of the existing chain and the phosphate on the new nucleotide undergo a condensation reaction, resulting in this bond. ● The phosphate on the new nucleotide is attached to the 5’ carbon atom of its sugar, and the linkage occurs between it and the 3’ carbon on the last sugar of the existing chain. Because each nucleotide is added to the 3’ carbon of the last sugar, nucleic acids are said to grow in the 5’ to 3’ direction. ➔ Nucleic Acids Size Nucleic acids range in size. Oligonucleotides are short, with about 20 nucleotide monomers, whereas polynucleotides are much longer ◆ Oligonucleotides include RNA molecules that function as ‘primers’ to begin the duplication of DNA; RNA molecule that regulate the expression of genes; and synthetic DNA molecule used for amplifying and analyzing other, longer nucleotide sequences. ◆ Polynucleotides, more commonly referred to as nucleic acids, include DNA and most RNA. They can be very long. Base Pairing Occurs in both DNA and RNA Distinguishing RNA from DNA Nucleic Acid Sugar Bases Name of Nucleoside Strands RNA Ribose Adenine Cytosine Guanine Uracil Adenosine Cytidine Guanosine Uridine Single DNA Deoxyribose Adenine Cytosine Guanine Thymine Deoxyadenosine Deoxycytidine Deoxyguanosine Deoxythymidine Double ➔ Complementary Base Pairing ◆ DNA- Thymine and Adenine always pair (T-A), and cytosine and guanine always pair (C-G). ◆ RNA- The base pairs are A-U and C-G ◆ Base pairs are held together by hydrogen bonds ◆ Double Helix- Two polynucleotide strands form a ‘ladder’ that twists. The sugar-phosphate groups form the sides of the ladder, and the bases with their hydrogen bonds form the ‘rungs’ on the inside. DNA Carries Information and is Expressed Through RNA ➔ DNA transmits info in 2 ways: ◆ DNA can be reproduced exactly. This is called DNA Replication. It is done by polymerization using an existing strand as a base-pairing template ◆ Certain DNA sequences can be copied in RNA, in a process called transcription. The nucleotide sequence in the RNA can then be used to specify a sequence of amino acids in a polypeptide chain. This process is called translation. The overall process of transcription and translation is called gene expression. ➔ 2 Important notes on DNA Replication/Transcription ◆ DNA replication and transcription depend on the base-pairing properties of nucleic acids. Recall that the hydrogen-bonded pairs are A-T & G-C in DNA & A-U and G-C in RNA. So… 5’-TCAGCA-3’= 3’AGTCGT-5’ ◆ DNA replication usually involves the entire DNA molecule. Since DNA holds essential info, it must be replicated completely and accurately so that each new cell or new organism receives a complete set of DNA from its parent. The complete set of DNA in a living organism is called its genome. However, not all of the info in the genome is needed at all times and in all tissues, and only small sections of the DNA are transcribed into RNA molecules. The sequence of DNA that are transcribed into RNA are called genes. Nucleotides Have Other Important Roles ➔ ATP (Adenosine triphosphate) acts as an energy transducer in many biochemical reactions. ➔ GTP (guanosine triphosphate) serves as an energy source, especially in protein synthesis. It also plays a role in the transfer of info from the environment to cells ➔ cAMP (cyclic adenosine monophosphate) is a special nucleotide with an additional bond between the sugar and the phosphate group. It is essential in many processes, including the actions of hormones and the transmission of info by the nervous system. ➔ Nucleotides play roles as carriers in the synthesis and breakdown of carbohydrates and lipids.
