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