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MutationsMutations
What Are What Are Mutations?Mutations?
Changes in the Changes in the nucleotide sequencenucleotide sequence of DNAof DNA
May occur in May occur in somatic somatic cellscells (aren’t passed to (aren’t passed to offspring)offspring)
May occur in May occur in gametesgametes (eggs & sperm) and (eggs & sperm) and be passed to offspringbe passed to offspring
Are Mutations Are Mutations Helpful or Helpful or Harmful?Harmful?
Mutations happen Mutations happen regularly regularly
Almost all mutations Almost all mutations are are neutral neutral
Chemicals & UVChemicals & UV radiation cause radiation cause mutationsmutations
Many mutations are Many mutations are repaired repaired by enzymesby enzymes
Are Mutations Are Mutations Helpful or Harmful?Helpful or Harmful?
Some type of Some type of skin skin cancers and cancers and leukemialeukemia result from result from somaticsomatic mutations mutations
Some mutations Some mutations may may improve improve an an organism’s organism’s survivalsurvival (beneficial)(beneficial)
Types of Types of MutationsMutations
Chromosome Chromosome MutationsMutations
May Involve:May Involve:– Changing theChanging the
structurestructure of a of a chromosomechromosome
– TheThe loss orloss or gaingain of part of of part of a chromosomea chromosome
Chromosome Chromosome MutationsMutations
Five types exist:Five types exist:– DeletionDeletion– InversionInversion– TranslocationTranslocation– NondisjunctionNondisjunction– DuplicationDuplication
DeletionDeletionDue to Due to breakagebreakageA A piecepiece of a of a chromosome is chromosome is lostlost
Chromosome MutationsChromosome Mutations
Cri-du-chatCri-du-chat– Deletion of material on Deletion of material on
55thth chromosome chromosome– Characterized by the cat-Characterized by the cat-
like cry made by cri-du-like cry made by cri-du-chat babieschat babies
– Varied levels of metal Varied levels of metal handicapshandicaps
InversionInversionChromosome Chromosome segment segment breaks breaks offoff
Segment flips Segment flips around around backwardsbackwards
Segment Segment reattachesreattaches
DuplicationDuplicationOccurs when a gene Occurs when a gene sequence is repeatedsequence is repeated
TranslocationTranslocation Involves Involves two two
chromosomeschromosomes that that aren’t homologousaren’t homologous
PartPart of one of one chromosome is chromosome is transferred to transferred to anotheranother chromosomeschromosomes
TranslocationTranslocation
NondisjunctionNondisjunction FailureFailure of chromosomes of chromosomes to to
separateseparate during meiosis during meiosis Causes gamete to have Causes gamete to have too manytoo many oror
too fewtoo few chromosomeschromosomes Disorders:Disorders:
– DownDown SyndromeSyndrome – – three 21three 21stst chromosomes chromosomes
– Turner Syndrome Turner Syndrome – – single X chromosomesingle X chromosome
– Klinefelter’s Syndrome Klinefelter’s Syndrome – – XXY XXY chromosomeschromosomes
Chromosome Chromosome Mutation Mutation AnimationAnimation
Gene MutationsGene Mutations Change in the Change in the nucleotide nucleotide
sequencesequence of a of a genegene May only involve a May only involve a single single
nucleotidenucleotide May be due to May be due to copying copying
errorserrors, , chemicalschemicals, , virusesviruses, etc., etc.
Types of Gene Types of Gene MutationsMutations
Include:Include:– Point MutationsPoint Mutations– SubstitutionsSubstitutions– InsertionsInsertions– DeletionsDeletions– FrameshiftFrameshift
Point MutationPoint Mutation
Change of a Change of a singlesingle nucleotide nucleotide
Includes the Includes the deletion, insertion, deletion, insertion, or substitution of or substitution of ONEONE nucleotide in nucleotide in a genea gene
Point MutationPoint Mutation
Sickle Cell Sickle Cell diseasedisease is the is the result of one result of one nucleotide nucleotide substitutionsubstitution
Occurs in the Occurs in the hemoglobin hemoglobin genegene
Frameshift Frameshift MutationMutation
Inserting or deletingInserting or deleting one or more one or more nucleotidesnucleotides
Changes the “Changes the “reading reading frameframe”” like changing a like changing a sentencesentence
ProteinsProteins built built incorrectlyincorrectly
Frameshift MutationFrameshift Mutation
Original:Original:– The fat cat ate the wee The fat cat ate the wee
rat.rat. Frame Shift (“a” added):Frame Shift (“a” added):
– The fat caThe fat caaa tet hew tet hew eer at.eer at.
Amino Acid Amino Acid Sequence ChangedSequence Changed
Gene Mutation Gene Mutation AnimationAnimation
HOX GENESHOX GENES
A series of genes that A series of genes that control the differentiation of control the differentiation of cells and tissues in the cells and tissues in the embryo. embryo.
Hox genes determine an Hox genes determine an animal’s basic body plananimal’s basic body plan
POLYDACTYLEPOLYDACTYLE
FYI FYI
Normal MaleNormal Male
302n = 46
Normal FemaleNormal Female
312n = 46
Male, Trisomy 21 Male, Trisomy 21 (Down’s)(Down’s)
322n = 47
Female Down’s Female Down’s SyndromeSyndrome
332n = 47
Female with Down’s Female with Down’s SyndromeSyndrome
Klinefelter’s SyndromeKlinefelter’s Syndrome
352n = 47
Sex Chromosome Sex Chromosome AbnormalitiesAbnormalities
Klinefelter’s Klinefelter’s SyndromeSyndrome– XXY, XXYY, XXXYXXY, XXYY, XXXY– MaleMale– SterilitySterility– Small testiclesSmall testicles– Breast enlargementBreast enlargement
XYY SYNDROMEXYY SYNDROME
Sex Chromosome Sex Chromosome AbnormalitiesAbnormalities
XYY SyndromeXYY Syndrome– Normal male traitsNormal male traits– Often tall and thinOften tall and thin– Associated with antisocial and behavioral Associated with antisocial and behavioral
problemsproblems
Turner’s SyndromeTurner’s Syndrome
392n = 45
Sex Chromosome Sex Chromosome MutationsMutations
Turner’s Turner’s SyndromeSyndrome– X0X0– FemaleFemale– sex organs don't sex organs don't
mature at adolescencemature at adolescence– sterilitysterility– short stature short stature – sterilitysterility– short stature short stature
Sex Chromosome MutationsSex Chromosome Mutations
XXXXXX– Trisomy XTrisomy X– FemaleFemale– Little or no visible differencesLittle or no visible differences– tall staturetall stature– learning disabilitieslearning disabilities– limited fertility limited fertility