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12-4 Mutations12-4 Mutations

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Mutation = change in genetic materialMutation = change in genetic material

Gene mutation = changes in a single geneGene mutation = changes in a single gene

Chromosomal mutation = changes in Chromosomal mutation = changes in whole chromosomes (affects many genes)whole chromosomes (affects many genes)

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Gene MutationsGene Mutations

Point MutationsPoint Mutations = Changes in one or a few = Changes in one or a few nucleotides nucleotides

Include: substitutions, insertions, and Include: substitutions, insertions, and deletionsdeletions

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Types of Point MutationsTypes of Point Mutations

Substitutions = one base is changed to Substitutions = one base is changed to anotheranother Usually affects a single amino acidUsually affects a single amino acid

Insertions = one base is inserted Insertions = one base is inserted Deletions = one base is deletedDeletions = one base is deleted

More dramatic changesMore dramatic changes Cause Cause frameshift mutationsframeshift mutations

• Changes all amino acids after the Changes all amino acids after the

point of changepoint of change

Frameshift MutationsFrameshift Mutations

mutation that shifts the “reading” frame of mutation that shifts the “reading” frame of the genetic message by inserting or the genetic message by inserting or deleting a nucleotidedeleting a nucleotide

May change every amino acid after that May change every amino acid after that pointpoint

Frameshift mutations can alter a protein so Frameshift mutations can alter a protein so much that it is unable to perform its normal much that it is unable to perform its normal functions.functions.

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Chromosomal MutationsChromosomal Mutations Changes in the number or structure of Changes in the number or structure of

chromosomeschromosomes

May even change the number of copies of May even change the number of copies of some genessome genes

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5 Types of Chromosomal Mutations5 Types of Chromosomal Mutations

Insertions = addition of part of a chromosomeInsertions = addition of part of a chromosome Deletions = loss of all or part of a chromosomeDeletions = loss of all or part of a chromosome Duplications = extra copies of parts of a Duplications = extra copies of parts of a

chromosomeschromosomes Inversions = reverse direction of parts of a Inversions = reverse direction of parts of a

chromosomeschromosomes Translocations = part of one chromosome Translocations = part of one chromosome

breaks off and attaches to another breaks off and attaches to another

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Chromosomal MutationsChromosomal Mutations

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Significance of MutationsSignificance of Mutations

Most have little effectMost have little effect Most mutations occur in portions of the DNA Most mutations occur in portions of the DNA

that is not currently being used.that is not currently being used. Dramatic changes = usually harmfulDramatic changes = usually harmful

Producing defective proteins that don’t do Producing defective proteins that don’t do their jobtheir job

Mutations = source of genetic variability!Mutations = source of genetic variability! Can be very good! Useful!Can be very good! Useful!

Polydactyly

12-5 Gene Regulation12-5 Gene Regulation

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A typical gene includes start and stop A typical gene includes start and stop signals, with the nucleotides to be signals, with the nucleotides to be translated in between. translated in between.

Regulatory Sites = determine if gene is on Regulatory Sites = determine if gene is on or off.or off.

LacLac Repressor in Repressor in

E. coliE. coli

Prokaryotic cellsProkaryotic cells Cells turn genes Cells turn genes

on and off as on and off as neededneeded

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Eukaryotic Gene RegulationEukaryotic Gene Regulation

Similar but more complex than prokaryotesSimilar but more complex than prokaryotes Many eukaryotic genes include a sequence Many eukaryotic genes include a sequence

called the TATA box that may help position called the TATA box that may help position RNA polymerase.RNA polymerase.

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Enhancer sequences in DNA: Protein Enhancer sequences in DNA: Protein binding area that canbinding area that can enhance transcription by opening up tightly enhance transcription by opening up tightly

packed chromatinpacked chromatin attract RNA polymeraseattract RNA polymerase block access to genesblock access to genes

More complex because of cell specializationMore complex because of cell specialization Not all proteins are needed in every cellNot all proteins are needed in every cell

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Chromosomal Chromosomal Mutations & their Mutations & their

effectseffects

KaryotypeKaryotype

A picture of the chromosomes of an A picture of the chromosomes of an individual (or a species), including individual (or a species), including number, form, and size of the number, form, and size of the chromosomes. chromosomes.

Often used to diagnosis Often used to diagnosis chromosomal abnormalities.chromosomal abnormalities.

ChromosomesChromosomes

Humans have 23 pairsHumans have 23 pairs 22 pairs are autosomes22 pairs are autosomes 1 pair are sex chromosomes 1 pair are sex chromosomes

•(women = XX, men = XY)(women = XX, men = XY) Chromosomes have a centromere that Chromosomes have a centromere that

holds the chromatids (two parts of the holds the chromatids (two parts of the chromosome) together.chromosome) together.

The top ½ of the chromosome is called The top ½ of the chromosome is called the “p” arm and the bottom ½ is “q”the “p” arm and the bottom ½ is “q”

Nondisjunction Nondisjunction DisorderDisorder

Nondisjunction is the failure of Nondisjunction is the failure of chromosome pairs to separate during chromosome pairs to separate during meiosis (making of gametes – sex cells)meiosis (making of gametes – sex cells)

it can cause some gametes to gain an it can cause some gametes to gain an extra chromosome and others to lose one extra chromosome and others to lose one

Monosomy = A chromosome having no Monosomy = A chromosome having no homologue (matching chromosome)homologue (matching chromosome)

Trisomy =The condition of having three Trisomy =The condition of having three copies of a given chromosome in each copies of a given chromosome in each somatic (body) cell rather than the normal somatic (body) cell rather than the normal number of two. number of two.

Normal Male Normal Male KaryotypeKaryotype

Normal Female Karyotype

Turners SyndromeTurners Syndrome

1 in 5,000 births

45 chromosomesX only #23 MonosomyNondisjunction

Turners SyndromeTurners Syndrome96-98% do not survive to birthNo menstruationNo breast developmentNo hipsBroad shoulders and neck

Cri-Du-Chat Cri-Du-Chat SyndromeSyndrome

1 in 216,000 births

46 chromosomesXY or XX

#5 Deletion of upper arm of chromosome

Cri-Du-Chat SyndromeCri-Du-Chat Syndrome

Moon-shaped faceHeart diseaseMentally retardedMalformed larynxNormal lifespan

Aniridia-Wilms Tumor Aniridia-Wilms Tumor SyndromeSyndrome

1 in 50,000,000 births

46 chromosomesXY or XX

#11 Deletion of upper arm

Aniridia-Wilms Tumor Aniridia-Wilms Tumor SyndromeSyndrome

Mentally retardedGrowth retardedBlindnessTumors on kidneysShort lifespan

Thirteen Q Deletion Thirteen Q Deletion SyndromeSyndrome

1 in 500,000 births

46 chromosomesXY or XX

#13 Deletion of lower arm

Thirteen Q Deletion Thirteen Q Deletion SyndromeSyndrome

Mentally retarded Deformed faceNo thumbs Heart diseaseShort lifespan

Prader-Willi Prader-Willi SyndromeSyndrome

1 in 5,000,000 births*(new info = 1 in 25,000)

46 chromosomesXY= 97% XX= 3%

#15 Deletion of lower armpaternal chromosome(Angelman’s syndrome = 15 q deletion of maternal chromosome)

Prader-Willi SyndromePrader-Willi Syndrome

Small bird-like head very flexibleMentally retarded low muscle toneRespiratory problemsObesityShort lifespan

Eighteen Q Deletion Eighteen Q Deletion SyndromeSyndrome

1 in 10,000,000 births

46 chromosomesXY or XX

#18 Deletion of lower arm

Eighteen Q Deletion Eighteen Q Deletion SyndromeSyndrome

Mentally retardedHeart diseaseAbnormal hands and feetLarge eyesLarge earsNormal lifespan

Cat-Eye SyndromeCat-Eye Syndrome

1 in 1,000,000 births

46 chromosomesXY or XX

#22 Deletion of bottom arm

Cat-Eye Cat-Eye SyndromeSyndrome

Fused fingers and toesMentally retardedSmall jawHeart problemsNormal lifespan

Four-Ring SyndromeFour-Ring Syndrome

1 in 10,000,000 births

46 chromosomesXY or XX

#4 Inversion

Four-Ring Four-Ring SyndromeSyndrome

Cleft palateClub feetTestes don’t descendShort lifespan

Down Down SyndromeSyndrome1 in 31,000 births

46 chromosomesXY=97%

XX=3%

#14/21 Translocation

1 in 1,250 births

47 chromosomes - XY or XX

#21 Trisomy Nondisjunction

Down Syndrome Trisomy

Down SyndromeDown Syndrome

Short, broad hands Stubby fingersRough skinImpotency in malesMentally retardedSmall round faceProtruding tongueShort lifespan

Edward’s Trisomy Edward’s Trisomy SyndromeSyndrome

1 in 4,400 births

47 chromosomesXX=80%

XY=20%

#18 Trisomy Nondisjunction

Edward’s Trisomy Edward’s Trisomy SyndromeSyndrome

Small headMentally retardedInternal organ abnormalities90% die before 5 months of age

Jacob’s SyndromeJacob’s Syndrome

1 in 1,800 births

47 chromosomes

XYY

#23 Trisomy Nondisjunction

Jacob’s SyndromeJacob’s Syndrome

Normal physicallyNormal mentallyIncrease in testosteroneAcneNormal lifespan

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Klinefelter SyndromeKlinefelter Syndrome

1 in 1,100 births

47 chromosomesXXY only

#23 Trisomy Nondisjunction

(sometimes seen as Kleinfelter)

Klinefelter Klinefelter SyndromeSyndrome

Scarce beardLonger fingers and armsSterileDelicate skinLow mental abilityNormal lifespan

Triple X SyndromeTriple X Syndrome

1 in 2,500 births

47 chromosomesXXX only

#23 TrisomyNondisjunction

Triple X SyndromeTriple X Syndrome

Normally physically Normal mentallyTallFertilenormal lifespan

This is a cell after it has been broken open. A photo is taken of this and then manipulated on a computer. Each chromosome is cut out of the photo.