Post on 14-Feb-2017
Chromosomal MutationsChromosomal Mutations
Changes in Chromosome Changes in Chromosome Number or StructureNumber or Structure
PRESENTED BY PRESENTED BY NAVEED UL MUSHTAQNAVEED UL MUSHTAQ
Chromosome MutationsChromosome Mutations
• A chromosome mutation is a change in A chromosome mutation is a change in the structure or arrangement of the the structure or arrangement of the chromosomeschromosomes
• Mutations are caused byMutations are caused by• Physical agents Physical agents e.g. X-rays and e.g. X-rays and
ultraviolet light ultraviolet light • Chemical mutagens Chemical mutagens such as nitrous acid such as nitrous acid
oror• By spontaneous By spontaneous way by unequal crossing way by unequal crossing
over.over.
Alterations in ChromosomeAlterations in ChromosomeStructural changesStructural changes•DELETIONDELETION•DUPLICATIONDUPLICATION•TRANSLOCATIONTRANSLOCATION•INVERSIONSINVERSIONSNUMERICAL CHANGESNUMERICAL CHANGES•AneuploidyExcess or Deficiency in a single chromosome•EUPLOIDY.Excess or Deficiency complete one or more sets of chromosomes
TYPES OF TYPES OF AneuploidyAneuploidy
• Monosomy (2n-1)Monosomy (2n-1)• NullisomyNullisomy• Trisomy(2n+1)Trisomy(2n+1)• Tetrasomy (2n+2)Tetrasomy (2n+2)
Human Chromosomal Human 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
AneuploidyAneuploidy• Arises by Non-disjunctionArises by Non-disjunction• Non-disjunction = failure of homologues Non-disjunction = failure of homologues
or chromatids to separate during meiosisor chromatids to separate during meiosis
Normal Normal MeiosisMeiosis
Non-disjunction Non-disjunction in Meiosis I in Meiosis I
Non-disjunction Non-disjunction in Meiosis II in Meiosis II
Incidence of Down Syndrome Increases with Maternal Age
1010 2020 3030 4040 505000
100100
200200
300300
400400
Age of Mother (years)Age of Mother (years)
Num
ber p
er 1
000
Birth
sNu
mbe
r per
100
0 Bi
rths
Human Chromosomal Human Chromosomal AneuploidsAneuploids
Sex Chromosome AneuploidsSex Chromosome Aneuploids
Turner SyndromeTurner Syndrome 45, XO45, XO
Triplo-XTriplo-X 47, XXX47, XXX
Klinefelter SyndromeKlinefelter Syndrome 47, XXY47, XXY
XYY SyndromeXYY Syndrome 47, XYY47, XYY
Sterile femaleSterile female
Fertile femaleFertile female
Sterile maleSterile male
Fertile maleFertile male
Applying KnowledgeApplying Knowledge
Lets determine how many Barr bodies would Lets 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
Klinefelter SyndromeKlinefelter Syndrome 47, XXY47, XXY
XYY SyndromeXYY Syndrome 47, XYY47, XYY
00
22
11
00
EuploidyEuploidy
Excess or Deficiency in the Excess or Deficiency in the number of the number of the entire entire chromomosomal complementchromomosomal complement
• MonoploidMonoploid• DiploidDiploid• TriploidTriploid• TetraploidTetraploid
Chromosome Structure Chromosome Structure ChangesChanges
ChangeChange Description Description DeletionDeletion Loss of a chromosomal Loss of a chromosomal
segment segment can occur terminally or internally
DuplicationDuplication Repeat of a chromosomal Repeat of a chromosomal segment segment
TranslocatioTranslocationn
Movement of chromosomal Movement of chromosomal segment to non-homologous segment to non-homologous chromosome or genes from chromosome or genes from one linkage group transferred one linkage group transferred to anotherto another
InversionInversion Reversal of a chromosomal Reversal of a chromosomal segment segment (rotated 180(rotated 180oo))
Chromosome Chromosome DeletionDeletion
in Humans in Humans
Cri-du-chat Cri-du-chat syndromesyndrome
is correlated withis correlated witha deletion at the enda deletion at the endof chromosome 5of chromosome 5 Deleterious effects, Deleterious effects,
pseudosominance, pseudosominance, absence of crossing absence of crossing over etcover etc
Chromosome Chromosome Duplication Duplication in Humansin Humans
Small duplications Small duplications in chromosome 15 in chromosome 15 cause no cause no symptoms and no symptoms and no deleterious effectsdeleterious effects
Large duplication Large duplication (with inversion) (with inversion) causes mental causes mental retardationretardation
Chromosome Chromosome Translocation Translocation
in Humansin Humans
Reciprocal Reciprocal Translocation Translocation involves exchange involves exchange between two non-between two non-homologous homologous chromosomeschromosomes
Reciprocal Reciprocal translocation translocation between between chromosomes chromosomes 2 and 20 causes 2 and 20 causes Alagille SyndromeAlagille Syndrome
Effects heart, liver, Effects heart, liver, kidneys etckidneys etc
Chromosome Translocation in Chromosome Translocation in HumansHumans
Robertsonian Translocation involves a fusion of the Robertsonian Translocation involves a fusion of the long arms of two different chromosomeslong arms of two different chromosomes
Translocation Down Syndrome involves a Robertsonian Translocation Down Syndrome involves a Robertsonian Translocation between chromosomes 14 and 21 Translocation between chromosomes 14 and 21
Chromosome Chromosome Inversions Lead to Inversions Lead to
Unbalanced Meiotic Unbalanced Meiotic ProductsProducts
A paracentric inversion does not include the
centromere
A pericentric inversion includes
the centromere
SIGNIFICANCE OF SIGNIFICANCE OF INVERSIONINVERSION
• ORIGIN OF NEW SPECIESORIGIN OF NEW SPECIES• PROOF FOR THE OCCURANCE PROOF FOR THE OCCURANCE
OF CROSSING OVEROF CROSSING OVER• INVERSION IS CONSIDERED INVERSION IS CONSIDERED
AS CROSSING OVER AS CROSSING OVER REPRESSORSREPRESSORS
THANK THANK YOUYOU
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