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MUTATIONS MUTATIONS Changes in Changes in DNA DNA that affect that affect genetic information. The genetic information. The ultimate source of ultimate source of variation in individuals. variation in individuals.

MUTATIONS Changes in DNA that affect genetic information. The ultimate source of variation in individuals

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Page 1: MUTATIONS Changes in DNA that affect genetic information. The ultimate source of variation in individuals

MUTATIONSMUTATIONSChanges in Changes in DNADNA that affect genetic that affect genetic information. The ultimate source of information. The ultimate source of variation in individuals.variation in individuals.

Page 2: MUTATIONS Changes in DNA that affect genetic information. The ultimate source of variation in individuals

What Causes Mutations?What Causes Mutations? There are two ways in which DNA can There are two ways in which DNA can

become mutated:become mutated: Mutations can be inherited.Mutations can be inherited.

Parent to childParent to child

Mutations can be acquired.Mutations can be acquired. Environmental damage due to mutagensEnvironmental damage due to mutagens Mistakes when DNA is copied Mistakes when DNA is copied

Page 3: MUTATIONS Changes in DNA that affect genetic information. The ultimate source of variation in individuals

What is a mutagen?What is a mutagen? Mutagens are factors that speed up Mutagens are factors that speed up

mutation rate. They include:mutation rate. They include: ionising radiation (x-rays, gamma rays ionising radiation (x-rays, gamma rays

and UV rays).and UV rays). Chemicals such as thalidomide, Chemicals such as thalidomide,

colchicine, mustard gas, acridine orange.colchicine, mustard gas, acridine orange.

Page 4: MUTATIONS Changes in DNA that affect genetic information. The ultimate source of variation in individuals

From studies of mutations From studies of mutations three main facts emerge:three main facts emerge: Mutations can arise spontaneously and are Mutations can arise spontaneously and are

in no sense directed by the environment.in no sense directed by the environment. Mutations are persistent. They tend to be Mutations are persistent. They tend to be

transmitted through many generations transmitted through many generations without further change.without further change.

The vast majority of mutations confer The vast majority of mutations confer disadvantages on the organisms that inherit disadvantages on the organisms that inherit them.them.

Page 5: MUTATIONS Changes in DNA that affect genetic information. The ultimate source of variation in individuals

Types of mutation: Types of mutation:

If the mutation occurs in the body cells If the mutation occurs in the body cells (is a somatic mutation it cannot be (is a somatic mutation it cannot be inherited by offspring).inherited by offspring).

If the mutation occurs in the If the mutation occurs in the reproductive cells (gametic cells) and reproductive cells (gametic cells) and is not lethal, it can be passed on to is not lethal, it can be passed on to the offspring and become part of the the offspring and become part of the gene pool.gene pool.

Page 6: MUTATIONS Changes in DNA that affect genetic information. The ultimate source of variation in individuals

Somatic mutationsSomatic mutations Occur in somatic (body cells)Occur in somatic (body cells) Affect parts of the body only.Affect parts of the body only. Can be passed on by mitosis when cells divide.Can be passed on by mitosis when cells divide. Can result in different cell lines in one organism eg Can result in different cell lines in one organism eg

one brown eye and one blue eye.one brown eye and one blue eye. Some cancers result from somatic mutations.Some cancers result from somatic mutations. Can be passed on by asexual reproduction eg Can be passed on by asexual reproduction eg

naval oranges, Royal Gala apples.naval oranges, Royal Gala apples. Not inheritable and only affect organism in their Not inheritable and only affect organism in their

lifetime.lifetime.

Page 7: MUTATIONS Changes in DNA that affect genetic information. The ultimate source of variation in individuals

Gametic mutationsGametic mutations Occur only in gametes (ova, sperm/pollen)Occur only in gametes (ova, sperm/pollen) These mutations occur during meiosis or in any These mutations occur during meiosis or in any

cells from which sex glands are derived i.e. during cells from which sex glands are derived i.e. during embryological development of the sex organsembryological development of the sex organs

InheritableInheritable Passed on by meiosis and fertilisationPassed on by meiosis and fertilisation If the mutation is survivable and the individual If the mutation is survivable and the individual

reproduces, the mutation can lead to new alleles reproduces, the mutation can lead to new alleles in the gene pool.in the gene pool.

If advantageous it will become more common in If advantageous it will become more common in the gene pool as a result of natural selection.the gene pool as a result of natural selection.

Page 8: MUTATIONS Changes in DNA that affect genetic information. The ultimate source of variation in individuals

Gene and chromosome Gene and chromosome mutationsmutations Gene mutations Gene mutations are chemical are chemical

changes in individual genes.changes in individual genes. Chromosome mutations Chromosome mutations involve involve

changes in the gross structure of changes in the gross structure of chromosomes.chromosomes.

Page 9: MUTATIONS Changes in DNA that affect genetic information. The ultimate source of variation in individuals

Gene MutationsGene Mutations Point Mutations – changes Point Mutations – changes in in

one or a fewone or a few nucleotides nucleotides SubstitutionSubstitution

THE FAT CAT ATE THE RATTHE FAT CAT ATE THE RAT THE FAT HAT ATE THE RATTHE FAT HAT ATE THE RAT

InsertionInsertion THE FAT CAT ATE THE RATTHE FAT CAT ATE THE RAT THE FAT CAT XLW ATE THE RATTHE FAT CAT XLW ATE THE RAT

DeletionDeletion THE FAT CAT ATE THE RATTHE FAT CAT ATE THE RAT THE FAT ATE THE RATTHE FAT ATE THE RAT

InversionInversion THE FAT CAT ATE THE RATTHE FAT CAT ATE THE RAT THE FAT CAT TEA THE RATTHE FAT CAT TEA THE RAT

Page 10: MUTATIONS Changes in DNA that affect genetic information. The ultimate source of variation in individuals

Gene MutationsGene Mutations Frameshift Mutations – shifts Frameshift Mutations – shifts

the the reading framereading frame of the genetic of the genetic message so that the message so that the protein protein may not be able to perform its may not be able to perform its function.function. InsertionInsertion

THE FAT CAT ATE THE RATTHE FAT CAT ATE THE RAT THE FAT HCA TAT ETH ERA TTHE FAT HCA TAT ETH ERA T

DeletionDeletion THE FAT CAT ATE THE RATTHE FAT CAT ATE THE RAT TEF ATC ATA TET HER ATTEF ATC ATA TET HER AT

H

H

Page 11: MUTATIONS Changes in DNA that affect genetic information. The ultimate source of variation in individuals

Disorders caused by gene Disorders caused by gene mutationsmutations

Sickle cell anaemia Sickle cell anaemia You can do some research on this.You can do some research on this.

Page 12: MUTATIONS Changes in DNA that affect genetic information. The ultimate source of variation in individuals

Chromosome MutationsChromosome Mutations Changes in number and structure of entire Changes in number and structure of entire

chromosomes chromosomes Original Chromosome Original Chromosome ABC * DEFABC * DEF DeletionDeletion AC * DEFAC * DEF DuplicationDuplication ABBC * DEFABBC * DEF InversionInversion AED * CBFAED * CBF TranslocationTranslocation ABC * JKLABC * JKL

GHI * DEFGHI * DEF

Page 13: MUTATIONS Changes in DNA that affect genetic information. The ultimate source of variation in individuals

Non disjunctionNon disjunction FailureFailure of chromosomes of chromosomes to separateto separate

during meiosisduring meiosis Causes gamete to have Causes gamete to have too many or too many or

too few chromosomestoo few chromosomes Disorders:Disorders:

Down Syndrome – three 21Down Syndrome – three 21stst chromosomes chromosomes Turner Syndrome – single X chromosomeTurner Syndrome – single X chromosome Klinefelter’s Syndrome – XXY chromosomesKlinefelter’s Syndrome – XXY chromosomes

Page 14: MUTATIONS Changes in DNA that affect genetic information. The ultimate source of variation in individuals

Significance of MutationsSignificance of Mutations• Most are neutralMost are neutral

• Eye colorEye color• Birth marksBirth marks

• Some are harmfulSome are harmful• Sickle Cell AnaemiaSickle Cell Anaemia• Down SyndromeDown Syndrome• cancerscancers

• Some are beneficialSome are beneficial• Sickle Cell Anaemia to MalariaSickle Cell Anaemia to Malaria• Immunity to HIVImmunity to HIV• You can do some research on the last pointYou can do some research on the last point

Page 15: MUTATIONS Changes in DNA that affect genetic information. The ultimate source of variation in individuals

Chromosome MutationsChromosome Mutations Down SyndromeDown Syndrome

Chromosome 21 does not Chromosome 21 does not separate correctly and the separate correctly and the child has 3 chromosome child has 3 chromosome number 21. This is called number 21. This is called trisomy.trisomy.

They have 47 chromosomes They have 47 chromosomes in stead of 46.in stead of 46.

Children with Down Children with Down Syndrome develop slower, Syndrome develop slower, may have heart and may have heart and stomach illnesses and vary stomach illnesses and vary greatly in their degree of greatly in their degree of intelligence.intelligence.

Page 16: MUTATIONS Changes in DNA that affect genetic information. The ultimate source of variation in individuals

Chromosome MutationsChromosome Mutations

Cri-du-chatCri-du-chat Deletion of material on 5Deletion of material on 5thth

chromosomechromosome Characterized by the cat-like Characterized by the cat-like

cry made by cri-du-chat cry made by cri-du-chat babiesbabies

Varied levels of mental Varied levels of mental handicapshandicaps

Page 17: MUTATIONS Changes in DNA that affect genetic information. The ultimate source of variation in individuals

Sex Chromosome Sex Chromosome AbnormalitiesAbnormalities Klinefelter’s Klinefelter’s

SyndromeSyndrome XXY, XXYY, XXXYXXY, XXYY, XXXY MaleMale SterilitySterility Small testiclesSmall testicles Breast enlargementBreast enlargement

Page 18: MUTATIONS Changes in DNA that affect genetic information. The ultimate source of variation in individuals

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

Page 19: MUTATIONS Changes in DNA that affect genetic information. The ultimate source of variation in individuals

Sex Chromosome MutationsSex Chromosome Mutations Turner’s SyndromeTurner’s Syndrome

X or XO - absence of one sex X or XO - absence of one sex chromosome. chromosome.

Foetuses with 22 pairs of Foetuses with 22 pairs of autosomes and a Y autosomes and a Y chromosome never survive to chromosome never survive to birthbirth

FemaleFemale sex organs don't mature at sex organs don't mature at

adolescenceadolescence sterilitysterility short stature short stature

Page 20: MUTATIONS Changes in DNA that affect genetic information. The ultimate source of variation in individuals

Sex Chromosome Sex Chromosome MutationsMutations

XXXXXX Trisomy XTrisomy X FemaleFemale Little or no visible differencesLittle or no visible differences tall staturetall stature learning disabilitieslearning disabilities limited fertility limited fertility

Page 21: MUTATIONS Changes in DNA that affect genetic information. The ultimate source of variation in individuals

PolyploidyPolyploidy Sometimes cell division fails altogether, Sometimes cell division fails altogether,

resulting in half the gametes having two of resulting in half the gametes having two of each type of chromosome (being diploid each type of chromosome (being diploid instead of haploid) and the rest having instead of haploid) and the rest having none.none.

If a diploid gamete fuses with a normal If a diploid gamete fuses with a normal haploid gamete the resulting individual is haploid gamete the resulting individual is triploid.triploid.

If two diploid gametes fuse the result is If two diploid gametes fuse the result is tetraploid.tetraploid.