際際滷

際際滷Share a Scribd company logo

Structural chromosomal aberration

Download as PPTX, PDF
Indu Sharma
Indu Sharma

A chromosomal disorder, anomaly, aberration, or mutation is a missing, extra, or irregular portion of chromosomal DNA. It can be from a typical number of chromosomes or a structural abnormality in one or more chromosomes. Chromosome mutation was formerly used in a strict sense to mean a change in a chromosomal segment, involving more than one gene. The term "karyotype" refers to the full set of chromosomes from an individual.

1 of 15
Downloaded 55 times
CHROMOSOMAL ABERRATION Prepared by : INDU SARMA 5th semester , Botany
CHROMOSOME Chromosomes are rod shaped or thread like condensed chromatin fibres which store and transmit coded hereditary information. The structure of chromosome consist of: Chromonema Primary constriction or centromere Secondary constriction Telomere
CHROMOSOMAL ABERRATION Mutations that cause change in the structure or number of chromosomes are called chromosomal aberration. These are of two types- Structural chromosomal aberrations (change in the structure of gene sequence). Numerical chromosomal aberrations (change in the number of chromosome). Factors responsible for chromosomal aberration are- Due to error in cell division. Maternal age and environment
STRUCTURAL CHROMOSOMAL ABERRATIONS Structural chromosomal aberration can be divided into four types- Deficiency or deletion Duplication Inversion Translocation Deletion and duplication involve alteration with certain chromosomal segment being lost or doubled. Inversion and translocation involve changes in position of chromosome segment.
DELETION OR DEFICIENCY The loss of a section of genetic material and genetic information from a chromosome structure. Deletion was the first structural aberration detected by Bridges in 1917 on X-chromosome of Drosophila. Deletion can be of two types- Terminal deletion- It involves a single break near the end of the chromosome. Intercalary deletion It involves two break in the middle portion.
EFFECTS OF DEFICIENCY Deficiency is useful in determining exact location of the gene on the chromosome. It will show pseudo dominance effect. Deficiency loop Formation takes place during synapsis. For example, in X-Chromosome of Drosophila, few bands are missing from the tip of X-band which result in formation of notches in wing margins in female fly.
DUPLICATION A structural change resulting in doubling of genes in a section of a chromosome. It can be intra-chromosomal duplication and inter-chromosomal duplication. Duplication can be of four types- Tandem duplication- The additional chromosome segment is located just after the normal segment, gene sequence being the same. Reverse tandem duplication: Same as above but the gene sequence of additional segment is inverted.
Displaced duplication- Here a sequence of chromosome get displaced in the same arm (intra arm) or in different arm (inter arm) of the chromosome. Transposed duplication- Here, duplicated gene sequence is attached to another position owing to inter chromosomal duplication.
EFFECT OF DUPLICATION Due to supply of additional genetic material and change genetic balance, they play important role in evolution at individual and population levels. For example: The theory of bar eye mutation in Drosophila is common example of duplication.
INVERSION It is an intra-chromosomal aberration, inversion of a chromosomal segment take place in intercalary position rotating at about 180 degree on its axis. It is of two types- Paracentric inversion: This inversion is confined to a single arm of chromosome and do not carry centromere. Pericentric inversion: In this type of inversion, break points are located in both arms of chromosome including centromere.
Effect of inversion: The location of inverted segment can be recognised by the presence of inversion loop during meiosis. Supressing of crossing over. Possibly the appearance of mutation owing to position effect.
TRANSLOCATION Integration of a chromosome segment into a non- homologous chromosome is known as translocation. Translocation are of two types: Non-reciprocal translocation and Reciprocal translocation Simple or terminal translocation: Here, terminal segment of a chromosome get integrated with a non-homologous chromosome.
Shift translocation or interstitial translocation: Here, an intercalary segment of a chromosome is integrated with a non-homologous chromosome. Reciprocal translocation: here, two non-homologous chromosome exchange their segments. This is the most common type of translocation.
Effect of translocation: It brings an qualitative change in the chromosome structure. It will bring about changes in the sequence of genes in chromosomes which may eventually produce several abnormalities in body characters. This is position effect. The most harmful effect of translocation is semi-sterility it causes.
Structural chromosomal aberration

More Related Content

Structural chromosomal aberration

  • 1. CHROMOSOMAL ABERRATION Prepared by : INDU SARMA 5th semester , Botany
  • 2. CHROMOSOME Chromosomes are rod shaped or thread like condensed chromatin fibres which store and transmit coded hereditary information. The structure of chromosome consist of: Chromonema Primary constriction or centromere Secondary constriction Telomere
  • 3. CHROMOSOMAL ABERRATION Mutations that cause change in the structure or number of chromosomes are called chromosomal aberration. These are of two types- Structural chromosomal aberrations (change in the structure of gene sequence). Numerical chromosomal aberrations (change in the number of chromosome). Factors responsible for chromosomal aberration are- Due to error in cell division. Maternal age and environment
  • 4. STRUCTURAL CHROMOSOMAL ABERRATIONS Structural chromosomal aberration can be divided into four types- Deficiency or deletion Duplication Inversion Translocation Deletion and duplication involve alteration with certain chromosomal segment being lost or doubled. Inversion and translocation involve changes in position of chromosome segment.
  • 5. DELETION OR DEFICIENCY The loss of a section of genetic material and genetic information from a chromosome structure. Deletion was the first structural aberration detected by Bridges in 1917 on X-chromosome of Drosophila. Deletion can be of two types- Terminal deletion- It involves a single break near the end of the chromosome. Intercalary deletion It involves two break in the middle portion.
  • 6. EFFECTS OF DEFICIENCY Deficiency is useful in determining exact location of the gene on the chromosome. It will show pseudo dominance effect. Deficiency loop Formation takes place during synapsis. For example, in X-Chromosome of Drosophila, few bands are missing from the tip of X-band which result in formation of notches in wing margins in female fly.
  • 7. DUPLICATION A structural change resulting in doubling of genes in a section of a chromosome. It can be intra-chromosomal duplication and inter-chromosomal duplication. Duplication can be of four types- Tandem duplication- The additional chromosome segment is located just after the normal segment, gene sequence being the same. Reverse tandem duplication: Same as above but the gene sequence of additional segment is inverted.
  • 8. Displaced duplication- Here a sequence of chromosome get displaced in the same arm (intra arm) or in different arm (inter arm) of the chromosome. Transposed duplication- Here, duplicated gene sequence is attached to another position owing to inter chromosomal duplication.
  • 9. EFFECT OF DUPLICATION Due to supply of additional genetic material and change genetic balance, they play important role in evolution at individual and population levels. For example: The theory of bar eye mutation in Drosophila is common example of duplication.
  • 10. INVERSION It is an intra-chromosomal aberration, inversion of a chromosomal segment take place in intercalary position rotating at about 180 degree on its axis. It is of two types- Paracentric inversion: This inversion is confined to a single arm of chromosome and do not carry centromere. Pericentric inversion: In this type of inversion, break points are located in both arms of chromosome including centromere.
  • 11. Effect of inversion: The location of inverted segment can be recognised by the presence of inversion loop during meiosis. Supressing of crossing over. Possibly the appearance of mutation owing to position effect.
  • 12. TRANSLOCATION Integration of a chromosome segment into a non- homologous chromosome is known as translocation. Translocation are of two types: Non-reciprocal translocation and Reciprocal translocation Simple or terminal translocation: Here, terminal segment of a chromosome get integrated with a non-homologous chromosome.
  • 13. Shift translocation or interstitial translocation: Here, an intercalary segment of a chromosome is integrated with a non-homologous chromosome. Reciprocal translocation: here, two non-homologous chromosome exchange their segments. This is the most common type of translocation.
  • 14. Effect of translocation: It brings an qualitative change in the chromosome structure. It will bring about changes in the sequence of genes in chromosomes which may eventually produce several abnormalities in body characters. This is position effect. The most harmful effect of translocation is semi-sterility it causes.