Chp 5 notes - Chapter 5: DNA and Chromosomes I....

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Chapter 5: DNA and Chromosomes I. Introduction A. DNA (deoxyribonucleic acid): material present in cells that contains the genetic information . In order for cells to maintain and reproduce themselves, they must be able to store, retrieve and translate the genetic instructions that are contained within their DNA. Every cell in your body has DNA and it is passed from a cell to its daughter cells at cell division. The genetic information in DNA is organized into units called genes . B. gene : a region of DNA that contains the instructions for making a particular protein (or a particular RNA); genes are arranged in long molecules of DNA that are present in the chromosomes C. chromosomes : long threadlike structures composed of DNA and associated proteins that carry the genetic information of an organism; these long DNA molecules are compacted inside the nucleus D. chromatin : complex of DNA and proteins (histones and other proteins) which makes up chromosomes E. genome : the complete set of information contained within an organism’s DNA. The term genome also refers to the sum total of DNA within an organism. F. Central Dogma of molecular biology: fundamental principle stating that genetic information flows from DNA to RNA to protein; this is true for all cells from bacteria to humans 1. genetic information is contained in DNA 2. DNA is transcribed to produce RNA 3. the information contained in RNA is decoded to produce proteins 4. proteins then go about doing work in the cell 5. exception: some RNAs are not translated into protein; noncoding RNAs 6. we will discuss this flow of information for the next several weeks E. Today, we’re going to start off by talking about the structure of DNA and how DNA is packaged into chromosomes that are present within the nucleus of the cell. II. DNA structure A. James Watson and Francis Crick determined the structure of DNA in 1953 . They later won the Nobel Prize for this discovery. They used X-ray diffraction to determine the three- dimensional structure of DNA. They found that DNA was composed of two strands wound into a helix ( double helix ). B. DNA molecule: 1. consists of two long polynucleotide chains (DNA chains or DNA strands); double stranded 2. each chain is composed of four types of nucleotides 3. a DNA nucleotide consists of: 5 carbon sugar (deoxyribose) single phosphate group one of four nitrogen-containing bases: adenine (A), cytosine (C), guanine (G), thymine (T); A and G (purines); C and T (pyrimidines) 4. the nucleotides are covalently linked together in a chain through the sugars and phosphates ( phosphodiester bonds ); alternating sugars and phosphates form a backbone with the bases coming off this backbone; the sugar-phosphate backbone is on the outside of the molecule and the bases are on the inside of the helix (Figure 5-2) 1
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5. the manner in which the nucleotide subunits are linked together gives each DNA strand polarity (the two ends are different); the ends are named chemical group present on the C that is
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Chp 5 notes - Chapter 5: DNA and Chromosomes I....

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