chromosomal mutation
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Changes in Chromosome Number or Structure
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chromosomal mutation
- 1. Chromosomal MutationsChromosomal Mutations Changes in ChromosomeChanges in Chromosome Number or StructureNumber or Structure PRESENTED BYPRESENTED BY NAVEED UL MUSHTAQNAVEED UL MUSHTAQ
- 2. Chromosome MutationsChromosome Mutations • A chromosome mutation is a change in theA chromosome mutation is a change in the structure or arrangement of thestructure or arrangement of the chromosomeschromosomes • Mutations are caused byMutations are caused by • Physical agentsPhysical agents e.g. X-rays and ultraviolete.g. X-rays and ultraviolet lightlight • Chemical mutagensChemical mutagens such as nitrous acid orsuch as nitrous acid or • By spontaneousBy spontaneous way by unequal crossingway by unequal crossing over.over.
- 3. Alterations in ChromosomeAlterations in Chromosome Structural changesStructural changes •DELETIONDELETION •DUPLICATIONDUPLICATION •TRANSLOCATIONTRANSLOCATION •INVERSIONSINVERSIONS NUMERICAL CHANGESNUMERICAL CHANGES •Aneuploidy Excess or Deficiency in a single chromosome •EUPLOIDY. Excess or Deficiency complete one or more sets of chromosomes
- 4. TYPES OFTYPES OF AneuploidyAneuploidy • Monosomy (2n-1)Monosomy (2n-1) • NullisomyNullisomy • Trisomy(2n+1)Trisomy(2n+1) • Tetrasomy (2n+2)Tetrasomy (2n+2)
- 5. Human ChromosomalHuman Chromosomal AneuploidsAneuploids Down SyndromeDown Syndrome Trisomy 21Trisomy 21 Edward SyndromeEdward Syndrome Trisomy 18Trisomy 18 Patau SyndromePatau Syndrome Trisomy 13Trisomy 13 Autosomal AneuploidsAutosomal Aneuploids Trisomy: three copies of one chromosomeTrisomy: three copies of one chromosome
- 7. AneuploidyAneuploidy • Arises by Non-disjunctionArises by Non-disjunction • Non-disjunction = failure of homologuesNon-disjunction = failure of homologues or chromatids to separate during meiosisor chromatids to separate during meiosis NormalNormal MeiosisMeiosis Non-disjunctionNon-disjunction in Meiosis Iin Meiosis I Non-disjunctionNon-disjunction in Meiosis IIin Meiosis II
- 8. Incidence of Down Syndrome Increases with Maternal Age 1010 2020 3030 4040 5050 00 100100 200200 300300 400400 Age of Mother (years)Age of Mother (years) Numberper1000BirthsNumberper1000Births
- 9. Human ChromosomalHuman Chromosomal AneuploidsAneuploids Sex Chromosome AneuploidsSex Chromosome Aneuploids Turner SyndromeTurner Syndrome 45, XO45, XO Triplo-XTriplo-X 47, XXX47, XXX KlinefelterKlinefelter SyndromeSyndrome 47, XXY47, XXY XYY SyndromeXYY Syndrome 47, XYY47, XYY Sterile femaleSterile female Fertile femaleFertile female Sterile maleSterile male Fertile maleFertile male
- 10. Applying KnowledgeApplying Knowledge Lets determine how many Barr bodies wouldLets determine how many Barr bodies would be found in each cell of someone withbe found in each cell of someone with:: Turner SyndromeTurner Syndrome 45, XO45, XO Triplo-XTriplo-X 47, XXX47, XXX KlinefelterKlinefelter SyndromeSyndrome 47, XXY47, XXY XYY SyndromeXYY Syndrome 47, XYY47, XYY 00 22 11 00
- 11. EuploidyEuploidy Excess or Deficiency in the numberExcess or Deficiency in the number of theof the entireentire chromomosomalchromomosomal complementcomplement • MonoploidMonoploid • DiploidDiploid • TriploidTriploid • TetraploidTetraploid
- 12. Chromosome Structure ChangesChromosome Structure Changes ChangeChange DescriptionDescription DeletionDeletion Loss of a chromosomalLoss of a chromosomal segmentsegment can occur terminally or internally DuplicationDuplication Repeat of a chromosomalRepeat of a chromosomal segmentsegment TranslocatioTranslocatio nn Movement of chromosomalMovement of chromosomal segment to non-homologoussegment to non-homologous chromosome or genes fromchromosome or genes from one linkage group transferredone linkage group transferred to anotherto another InversionInversion Reversal of a chromosomalReversal of a chromosomal segmentsegment (rotated 180(rotated 180oo ))
- 13. Chromosome DeletionChromosome Deletion in Humansin Humans Cri-du-chat syndromeCri-du-chat syndrome is correlated withis correlated with a deletion at the enda deletion at the end of chromosome 5of chromosome 5 Deleterious effects,Deleterious effects, pseudosominance,pseudosominance, absence of crossingabsence of crossing over etcover etc
- 14. ChromosomeChromosome DuplicationDuplication in Humansin Humans Small duplicationsSmall duplications in chromosome 15in chromosome 15 cause no symptomscause no symptoms and no deleteriousand no deleterious effectseffects Large duplicationLarge duplication (with inversion)(with inversion) causes mentalcauses mental retardationretardation
- 15. ChromosomeChromosome TranslocationTranslocation in Humansin Humans ReciprocalReciprocal Translocation involvesTranslocation involves exchange between twoexchange between two non-homologousnon-homologous chromosomeschromosomes ReciprocalReciprocal translocation betweentranslocation between chromosomeschromosomes 2 and 20 causes2 and 20 causes Alagille SyndromeAlagille Syndrome Effects heart, liver,Effects heart, liver, kidneys etckidneys etc
- 16. Chromosome Translocation in HumansChromosome Translocation in Humans Robertsonian Translocation involves a fusion of the longRobertsonian Translocation involves a fusion of the long arms of two different chromosomesarms of two different chromosomes Translocation Down Syndrome involves a RobertsonianTranslocation Down Syndrome involves a Robertsonian Translocation between chromosomes 14 and 21Translocation between chromosomes 14 and 21
- 17. Chromosome InversionsChromosome Inversions Lead to UnbalancedLead to Unbalanced Meiotic ProductsMeiotic Products A paracentric inversion does not include the centromere A pericentric inversion includes the centromere
- 18. SIGNIFICANCE OF INVERSIONSIGNIFICANCE OF INVERSION • ORIGIN OF NEW SPECIESORIGIN OF NEW SPECIES • PROOF FOR THE OCCURANCEPROOF FOR THE OCCURANCE OF CROSSING OVEROF CROSSING OVER • INVERSION IS CONSIDERED ASINVERSION IS CONSIDERED AS CROSSING OVER REPRESSORSCROSSING OVER REPRESSORS
- 19. THANK YOUTHANK YOU End of slide showEnd of slide show
Editor's Notes
- Figure: FIGURE 12.20 Title: Down syndrome frequency increases with maternal age Caption: The increase in frequency of Down syndrome after maternal age 35 is quite dramatic.