Biology Study Guide 2

Biology Study Guide 2 - Biology Study Guide Test 2 DNA DNA...

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Biology Study Guide Test 2 DNA DNA is a nucleic acid made of long chains of nucleotide monomers . Nucleotide monomers are composed of a sugar (deoxyribose) and a phosphate (the backbone), and nitrogenous base. DNA has 4 types of nitrogenous bases: o T—Thymine (pyrimidines) o C—Cytosine (pyrimidines) o A—Adenine (purines) o G—Guanine (purines) James Watson and Francis Crick worked out the three-dimensional structure of DNA, based on work by Rosalind Franklin. The structure of DNA consists of two polynucleotide strands wrapped around each other in a double helix. Hydrogen bonds between bases hold the strands together. A pairs with T and C pairs with G .
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DNA REPLICATION Replication starts with the separation of DNA strands. Each strand becomes a template to assemble new nucleotides into complementary strands. Picture: parent strand splits and doubles and then forms 2 separate (daughter) strands. DNA replication is a complex process, due in part to the fact that some of the helical DNA molecule must untwist. Replication happens quickly. o 50 nucleotides added every second (mammels) o 500 added every second (bacteria) Replication has few errors because… o DNA has a proofreading enzyme o DNA has a repair enzyme. o Only about one in a billon nucleotides are mispaired. TRANSCRIPTION The DNA of the gene is transcribed into RNA, which is translated into the polypeptide.
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Transcription produces genetic messages in the form of RNA. Three stages of transcription: o Initiation o Elongation o Termination Eukaryotic RNA is processed before leaving the nucleus RNA that is used to make proteins = mRNA TRANSLATION The DNA of the gene is transcribed into RNA, which is translated into the polypeptide. Genetic information written in codons is translated into amino acid sequences The codons in a gene specify the amino acid sequence of a polypeptide. Nearly all organisms use exactly the same genetic code. Each codon is translated into one (specific) amino acid. MUTATION Mutations are changes in the DNA base sequence caused by some error in DNA or by mutagens.
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Mutations can alter in 3 different ways: o Substituting o Inserting o Deleting VIRUSES Viruses are genes packaged in protein. Viral DNA may become part of the host chromosome.
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This note was uploaded on 04/07/2008 for the course BIOL 1543 taught by Professor Roberts during the Spring '08 term at Arkansas.

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Biology Study Guide 2 - Biology Study Guide Test 2 DNA DNA...

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