Mutations Some Se Non-Homologous Chromosomes Even Exchanged

Home , Frameshift mutation, Point mutation

CorrectionKey=A DO NOT EDIT--Changes mustbemadethrough “File info” 146 8.7 Holt McDougal Biology entire chromosome. an others affect asingle affect gene, while mutations Some se non-homologous chromosomes even exchanged. might be result inchromosomes two thesamegene. copies with of Pieces of exchange pieces. Errors incrossing meiosis can over of or inother parts Recall that crossing over process isanormal inwhich chromosomes achromosome.Errors inmeiosis canresult of inchanges inlarge parts Chromosomal M gene mutations. There of are different types M Gene chromosome. awhole meiosis andaffect can alsohappen during gene. replicationtion canhappen during asingle andaffect A mutation amutation meansachangeIn inanorganism’s biology DNA. A muta - • • c protein mRNA DNA Frameshift mutation (insertion) protein mRNA DNA Normal ti added, or inserted. anucleotide is reading isalsoshifted if frame result is “THC ATA TETHER AT…” The first “THE,” thereading isshifted. frame The the letter Eisremoved, or deleted, from the to thesentence CAT“THE ATE THERAT.” If reading from frame 8.5. Section back Think reading frame. the Recall of theimportance sequence. results This inachange inthe or anucleotide removal intheDNA of mutation istheaddition A frameshift acid. glutamic of instead acid isadded—aspartic amino acid to aCTA codon. As aresult, thewrong shows aCTCthe right codon thatischanged nently changed. For example, thefigure to by DNA polymerase, theDNA isperma replication.during theerror isnotfixed If nucleotide isput into aDNA molecule mutationA point anincorrect iswhen o n

utations chromosomal mutation? What isthedifference between agene mutation anda G G C C Leu Leu U U A A may ormay not affect phenotype. Key Concept Mutations A A T T G G C C Glu Glu utations A A T T G A T C G U A C Ser Val G U C A Mutations are changes inDNAthat G G C C G G C C Asp Arg G A C T U A A T U A added base T

A Ty Frameshift mutation (deletion) Point mutation Normal protein mRNA DNA protein mRNA DNA Frameshift mutation (insertion) protein mRNA DNA protein mRNA DNA mutation Mutat of pes G G C C G G C C isachange inanorganism’s DNA. Leu Leu Leu Leu U U A A U U A A A A T T A A T T ion G G C C G G C C Glu Asp Glu Glu A A T T A A T T s G U C A G A T C U A U A G U A C Ser Ser Ser G G Val C C G U C A G C G C G G C C G C T A G G C C

Asp Asp 6E Arg Ile A A U T G A C T U A A U U A A T U A mutated deleted added base base base G A T

© Houghton Mifflin Harcourt Publishing Company Frameshift mutation (deletion) Point mutation DNA mRNA protein DNA mRNA protein G G C C Leu Leu U U A A A A T T G G C C Glu Asp A A T T G U C A U A U A Ser Ser G G C C G C G C G C T A Asp Ile A A U T U A A U mutated deleted base base G A CorrectionKey=A DO NOT EDIT--Changes mustbemadethrough “File info”

© Houghton Mifflin Harcourt Publishing Company M M Other mutations are by caused intheenvironment. things Some mutations areerrors inthecell. thathappen theresultnormally of mutations canhappen faster thanthebody’s repair system canwork. DNA hasa polymerase “proofreading” to function fixerrors. However, Mutations happen. But cells have tools to repair them. For example, things. Whether amutation depends anorganism on many affects different • • • • • cancaused be utations by several factors. mayutations may or phenotype. affect not of aging. of mutations isamajor cause There thatabuild-up of isevidence more errors. Eventually thesemutations how affect thecell works. errors are number not fixed.small of Over time, there are more and Replication errors to offspring. onpassed to offspring. Mutations inbodyon cells passed cannotbe Type ofcell from binding to itssubstrate. could andprevent change anenzyme theactive the enzyme site of prevent theprotein from functioning. For example, amutation the resulting protein’s or function. shape Otherchanges might Impact ontheresulting protein oneffect theresulting aminoacid. thiscodontion thatchanges thelastnucleotide would of have no CGU, CGC, CGA, code andCGGall for arginine. A pointmuta- than one codon cancode for thesameaminoacid. For example, place. A pointmutation may alsohave noeffect. Recall thatmore changed into astop codon, would end atthewrong transcription havestill abig effect. For example, a codon for is anaminoacid if Impact ontheaminoacid sequence many reading andcanaffect whole frame codons. mutationframeshift usuallyitchanges hasabigger because effect the Type ofmutation

organism’s phenotype. Give oneexample ofamutation that would not affect an Recall thatmutations thatoccur cells ingerm canbe A pointmutation only one codon. affects A DNA proofreads polymerase replication, but a Some changes might not affect notaffect Some changes might A change inone codon can

stop codon. a codonforcysteineinto This pointmutationchanged U U U U G G G G Interactive Reader A A C C stop cysteine 147 CorrectionKey=A DO NOT EDIT--Changes mustbemadethrough “File info” 148 Holt McDougal Biology 4. 3. 2. 1. point mutation mutation cancer may result. 8.7 8.7 • type andonemutation that not will affect phenotype. Give anexample ofonemutation that affect will anorganism’s pheno- or anentire chromosome? Explain. Is amutation that happens duringmeiosis likely to affect asingle gene mutation? What isthedifference between apointmutation andaframeshift What isthedifference between amutation andamutagen? If mutations causechanges thecontrol thataffect If over cell division, mutagens. intheenvironmentThings thatcanchange DNA are called can causeDNA mutations—such andsome chemicals. asUVlight Mutagens

What are two examples ofmutagens? BigPicture The V Check ocabulary Some conditions andsubstances intheenvironment mutagen frameshift mutation word inbold. has avocabulary each sentence that Go back andhighlight Mark

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