CHROMOSOMAL ABBERATIONSCHROMOSOMAL ABBERATIONS

PRESENTED BYPRESENTED BYPOOJA PANDEYPOOJA PANDEY

( M. Sc Biotechnology 2( M. Sc Biotechnology 2ndnd sem ) sem )

DEPARTMENT OF BIOTECHNOLOGYDEPARTMENT OF BIOTECHNOLOGY

IIS UNIVERSITYIIS UNIVERSITY

UNDER GUIDANCE OFUNDER GUIDANCE OFMrs. CHARU SHARMAMrs. CHARU SHARMA

INTRODUCTION:-INTRODUCTION:-

• Visible change in chromosome structure Visible change in chromosome structure or chromosome arrangement.or chromosome arrangement.

• It is of 2 types:-It is of 2 types:-

1)1) Variation in chromosome structure Variation in chromosome structure

2)2) variation in chromosome number.variation in chromosome number.

VARIATION IN CHROMOSOME VARIATION IN CHROMOSOME STRUCTURE:-STRUCTURE:-

• It is studied in polytene chromosome ( it It is studied in polytene chromosome ( it consist chromatid bundles resulting from consist chromatid bundles resulting from endoreduplication)endoreduplication)

• It is of 4 types:-It is of 4 types:-

1)1) Deletion or deficiencyDeletion or deficiency

2)2) Duplication Duplication

3)3) TranslocationTranslocation

4)4) InversionInversion..

DEFICIENCY OR DELETION:-DEFICIENCY OR DELETION:-

• Deletion of a chromosome segment Deletion of a chromosome segment resulting in loss of genes.resulting in loss of genes.

• It can be done by spontaneous or It can be done by spontaneous or induced process.induced process.

• Chromosomes with deletion can Chromosomes with deletion can never revert to a normal condition .never revert to a normal condition .

• Example:- Cri-du-Chat Example:- Cri-du-Chat syndrome( deletion of part of short syndrome( deletion of part of short arm of chromosome 5).arm of chromosome 5).

• It is of 2 types:-It is of 2 types:-

1)1) Terminal deletion Terminal deletion

2)2) Intercalary deletionIntercalary deletion

DUPLICATION:-DUPLICATION:-• Presence of same block of gene more than once Presence of same block of gene more than once

in haploid complement is called as Duplication, in haploid complement is called as Duplication, and additional block of gene is called a repeat.and additional block of gene is called a repeat.

• It can be of 3 types:-It can be of 3 types:-1) Tandem duplication 1) Tandem duplication 2) Reverse tandem duplication2) Reverse tandem duplication3) Terminal tandem duplication3) Terminal tandem duplication• Occur by unequal crossing overOccur by unequal crossing over or by attachment of a deletedor by attachment of a deleted part from 1 chromosome to other.part from 1 chromosome to other.• example:- Bar mutant in example:- Bar mutant in Drosoplhila melanogaster.Drosoplhila melanogaster.

TRANSLOCATION:-TRANSLOCATION:-

• No gain or loss of genetic material.No gain or loss of genetic material.

• Change in position of chromosome segment.Change in position of chromosome segment.

• It can be of 2 types:-It can be of 2 types:-

1)1) Non reciprocalNon reciprocal

translocationtranslocation

2) Reciprocal translocation2) Reciprocal translocation

TRANSLOCATION:-TRANSLOCATION:-

• BEHAVIOUR OF TRANSLOCATION ZYGOTESBEHAVIOUR OF TRANSLOCATION ZYGOTES :- :-1)Homozygous translocation1)Homozygous translocation2)Reciprocal translocation heterozygotes2)Reciprocal translocation heterozygotes a) alternate segregationa) alternate segregation b) adjacent –I segregationb) adjacent –I segregation c) adjacent – 2 segregationc) adjacent – 2 segregation• It cause change in morphology of chromosome.It cause change in morphology of chromosome.• It also induce polymorphism in populationIt also induce polymorphism in population• Example:- Philadelphia chromosome in chronic Example:- Philadelphia chromosome in chronic

myelogenous leukemia by a reciprocal myelogenous leukemia by a reciprocal translocation involving chromosomes 9 and 22.translocation involving chromosomes 9 and 22.

INVERSION:-INVERSION:-• sequence of genes is altered by the sequence of genes is altered by the

rotation of gene block within a rotation of gene block within a chromosome by 180 degreechromosome by 180 degree

• Types of inversion:-Types of inversion:-

1)Paracentric inversion1)Paracentric inversion

2)Pericentric inversion2)Pericentric inversion

• Effects of inversionEffects of inversion

on phenotype may be on phenotype may be

produced because ofproduced because of

position effectposition effect

PERICENTRIC INVERSION:-PERICENTRIC INVERSION:-• When a pericentric inversion When a pericentric inversion

crosses over with a normal crosses over with a normal chromosome, the resulting chromosome, the resulting chromosomes are both chromosomes are both duplicated for some genes duplicated for some genes and deleted for other genes. ) and deleted for other genes. ) The gametes resulting from The gametes resulting from these are aneuploid and do these are aneuploid and do not survive. not survive.

• Thus, either kind of inversion Thus, either kind of inversion has lethal results when it has lethal results when it crosses over with a normal crosses over with a normal chromosome. The only chromosome. The only offspring that survive are offspring that survive are those that didn't have a those that didn't have a crossover, so it appears that crossover, so it appears that crossing over has been crossing over has been suppressed.suppressed.

PARACENTRIC INVERSIONPARACENTRIC INVERSION:-:-• When a paracentric When a paracentric

inversion crosses over inversion crosses over with a normal with a normal chromosome, the chromosome, the resulting chromosomes resulting chromosomes are an acentric, with no are an acentric, with no centromere, and a centromere, and a dicentric, with 2 dicentric, with 2 centromeres. centromeres.

• The acentric The acentric chromosome isn't chromosome isn't attached to the spindle, attached to the spindle, so it gets lost during cell so it gets lost during cell division, and the dicentric division, and the dicentric is usually pulled apart is usually pulled apart (broken) by the spindle (broken) by the spindle pulling the two pulling the two centromeres in opposite centromeres in opposite directions. These directions. These conditions are lethal.conditions are lethal.

VARIATION IN CHROMOSOME VARIATION IN CHROMOSOME NUMBER:-NUMBER:-

• Due to non disjunction numerical changes in Due to non disjunction numerical changes in chromosome number occur.chromosome number occur.

• The phenomenon of variations in the number of The phenomenon of variations in the number of chromosomes is called heteroploidy. It is of 2 types chromosomes is called heteroploidy. It is of 2 types a :-a :-

• 1) 1) EUPLOIDY EUPLOIDY 2)ANEUPLOIDY2)ANEUPLOIDY

Monoploidy :-Monoploidy :-

• Have only 1 set of chromosome. Have only 1 set of chromosome. While haploids have half the somatic While haploids have half the somatic chromosome number.chromosome number.

• Naturally develop or can be induced.Naturally develop or can be induced.

Polyploidy:-Polyploidy:-• Organism with more than 2 set of chromosomes are Organism with more than 2 set of chromosomes are

called polyploids.called polyploids.• PolyploidsPolyploids may arise spontaneously or be induced may arise spontaneously or be induced

experimentally .experimentally .• general classes of polyploids: general classes of polyploids: having odd number having even number of having odd number having even number of of chromosomes sets chromosome setsof chromosomes sets chromosome sets• Based on the source of additional chromosome sets:-Based on the source of additional chromosome sets:- PolyploidsPolyploids Autopolyploids AllopolyploidsAutopolyploids Allopolyploids

• Raphanobrassica the first known Raphanobrassica the first known tetraploid reported by Russian tetraploid reported by Russian geneticist karpenchenko.geneticist karpenchenko.

Aneuploidy :-Aneuploidy :-• is the addition or loss of one or more chromosomes to the is the addition or loss of one or more chromosomes to the

complete diploidcomplete diploid chromosome complement of an chromosome complement of an organismorganism. .

• Aneuploiy can be of 2 typesAneuploiy can be of 2 types

1) Hyperploidy 2) Hypoploidy1) Hyperploidy 2) Hypoploidy

Genetic disorders:-Genetic disorders:-• Down’s syndrome:-Down’s syndrome:- Due to trisomy of 21Due to trisomy of 21stst chromosome. chromosome. Other syndromes are like Turner’s syndrome, Klinefelter Other syndromes are like Turner’s syndrome, Klinefelter

syndrome etc.syndrome etc.

microgenia (an abnormally small chin) a

THANK YOUTHANK YOU