15BIS101F2013MutatLect15

Required g c hno2 g 1st dna u replication u 2nd dna a

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Unformatted text preview: ounds of DNA Replication Two rounds of DNA replications are needed to “fix” a Two mutation in the chromosome. mutation BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez 31 Chemical Mutagens: Nitrous Acid (HNO2) Nitrous Acid (HNO2) deaminates cytosine and adenine to produce uracil and hypoxanthin (Hx), respectively. Uracil can bond to A while hypoxanthin can bond to C. Nitrous acid produces a GC to AT transitions and TA to CG transitions. Note that two rounds of DNA replication are required to fix the mutation into the gene. required ­ G C HNO2 G 1st DNA U replication U 2nd DNA A replication A T BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez 32 Nitrous Acid (HNO2) Nitrous Acid (HNO2) deaminates cytosine and adenine to produce uracil and hypoxanthin (Hx), respectively. Uracil can bond to A while hypoxanthin can bond to C. Nitrous acid produces a GC to AT transitions and TA to CG transitions. Note that two rounds of DNA replication are required to fix the mutation into the gene. required ­ T A HNO2 T 1st DNA Hxreplication Hx Hx Hx 2nd DNA C replication C G BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez 33 Hydroxylamine (NH2OH) Hydroxylamine (NH2OH) adds an OH group in place of the NH2 group on cytosine. This produces hydroxylaminocytosine (or N-4-Hydroycytosine), which can bind to adenine. NH2OH generates GC to AT transitions. which BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez 34 Hydroxylamine (NH2OH) Hydroxylamine (NH2OH) adds an OH group in place of the NH2 group on cytosine. This produces hydroxylaminocytosine (or N-4-Hydroycytosine), which can bind to adenine. NH2OH generates GC to AT transitions. which G C NH2OH G 1st DNA C*replication C* C* C* 2nd DNA A replication A T BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez ©2013 BIS101­001, Spring 2013—Genes and Gene Expression R.L. Rodriguez 35 Chemical Mutagens Alkylating Agents: Ethyl methanesulfonate (EMS), ethyl Ethyl ethanesulfonate (EES) and methyl methane-sulfonate (MMS) all add alkyl groups such a ethyl or methyl groups to the oxygen on purines and pyrimidines. O-6 ethylguanine is a good example of how EMS works. This produces a GC to AT transition. Alkylating agents can also produce the following transversions: GC to CG, AT to TA, GC to TA and AT to CG. transversions: Acridine compounds. Examples, proflavin and acridine Examples, orange. These compounds insert themselves between stacked base pairs in double stranded DNA and are therefore called intercalating agents. During the process of DNA intercalating During replication, single base insertions or deletions are produced. This causes f...
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This note was uploaded on 02/12/2014 for the course BIS 101 taught by Professor Simonchan during the Spring '08 term at UC Davis.

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