week-04e-DNA-replic-mitosis-meiosis-genetics - BIOL 101 -...

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Week 4 - Page - 1- Figure 1 . Double stranded DNA Figure 2 . Bases (pyrimidines; purines) and sugars in nucleic acids BIOL 101 - Fall 2007- Week 4 - Nucleic acids - Replication - Mitosis-Meiosis NUCLEIC ACIDS Nucleic acids are the repository of genetic information for life forms on planet Earth. They consist of linear molecules containing repeat units of: sugar (ribose or deoxyribose) - base 0 phosphate 0 sugar (ribose or deoxyribose) - base 0 phosphate 0 DNA and RNA can be single-stranded (ss) or double- stranded (ds) (Fig. 1). When ds, the strands are present as an antiparallel double helix , in which, for DNA : A pairs with T and, for RNA : A pairs with U G pairs with C . G pairs with C Bases in nucleic acids are: purines or pyrimidines . See Fig. 2. Purines adenine ( A ) and guanine ( G ) are present in DNA and RNA. ["AGs are pure"] Pyrimidines thymine ( T ) and cytosine ( C ) are in DNA uracil ( U ) and cytosine ( C ) are in RNA. Ribonucleic acid ( RNA )
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Week 4 - Page - 2- Ribonucleic acid (RNA) contains ribose sugars whereas Deoxyribonucleic acid ( DNA ) contains deoxyribose sugars. Adenosine is the structure: adenine+sugar, a nucleoside . Adenosine phosphate is: adenine+sugar+phosphate, a nucleotide . Adenosine diphosphate is: adenine+sugar+phosphate+phosphate ( ADP ) Adenosine triphosphate is: adenine+sugar+phosphate+phosphate+phosphate ( ATP ) You should remember these structures - especially ribose and deoxyribose!! Rosalind Franklin and Maurice Wilkins Obtained the data that led to deciphering the structure of DNA. James Watson and Francis Crick In 1953 made the final intuitive steps leading to the discovery of the double helix structure of DNA, for which, with Maurice Wilkins, they were awarded a Nobel Prize in 1962. Subsequently, it was realized that DNA is copied ( transcribed ) into RNA and that this RNA is exported from the nucleus into the cytoplasm where it serves as a template for the ordered assembly of amino acids into protein. See the textbook - Stern 9 edn. p233-241 - and later lecture notes for th more details. The textbook accentuates the work of Barbara McClintock. This was certainly important (McClintock was awarded a Nobel Prize) but, in many ways, the transposable elements she discovered relate more directly to epigenetics than to genetics. REPLICATION AND THE CELL CYCLE Genetic Information Heritable information encoding plant form and function is carried in DNA. Permutations of four bases, A, C, G and T provide instructions for RNA synthesis (bases in RNA are A, C, G and U) which, in turn, direct the synthesis of proteins. Watson and Crick recognized that, since DNA consists of two antiparallel strands, replication could result from unwinding and copying of these strands. The pairing between A and T and G and C explained the long-known 1:1 ratio for these nucleotides. DNA sequences are read from 5' to 3' (from the free phosphate on carbon 5 of ribose at one end to the free OH on carbon 3
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This note was uploaded on 03/25/2008 for the course BIOL 101 taught by Professor Hall during the Fall '07 term at Texas A&M.

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week-04e-DNA-replic-mitosis-meiosis-genetics - BIOL 101 -...

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