28 Questions
What is the result of break at or near the centromere in two acrocentric chromosomes during Robertsonian translocation?
Fusion of their long arms with loss of fragment formed by fusion of their short arms
What is the characteristic of a carrier with a Robertsonian translocation?
They are normal because the lost short arms do not carry important genetic material
What type of translocation involves the exchange of genetic material between two non-homologous chromosomes?
Reciprocal translocation
What is the consequence of a balanced reciprocal translocation?
No loss of genetic material
How can a normal carrier of a Robertsonian translocation produce an offspring with Down syndrome?
Through a translocation of a chromosome during meiosis
What type of translocation is always unbalanced?
Deletion
What is the result of a Robertsonian translocation in terms of chromosome number?
Reduced chromosome number
What type of chromosomal abnormalities may be balanced or unbalanced?
Inversions, insertions, reciprocal translocations, and Robertsonian translocations
What is the main difference between reciprocal translocation and Robertsonian translocation?
The location of genetic material exchange
Which type of translocation can result in a balanced or unbalanced karyotype?
Both reciprocal and Robertsonian translocation
What is the characteristic of a derivative chromosome in reciprocal translocation?
It is a result of exchange of genetic material between two non-homologous chromosomes
What happens to the short arms in a Robertsonian translocation?
They are lost
What is the outcome of a balanced reciprocal translocation in terms of chromosome number?
The number of chromosomes remains the same
What is the characteristic of a deletion?
It is always unbalanced
What is the karyotype of a carrier with a Robertsonian translocation?
45,XX,-14,-21,+t(14q21q)
What is the difference between reciprocal translocation and inversion?
The orientation of genetic material exchange
Which type of chromosomal abnormality can result in a Down syndrome?
Robertsonian translocation
What is the common characteristic of isochromosomes and ring chromosomes?
They are always unbalanced
What is the main consequence of a reciprocal translocation between two non-homologous chromosomes?
No loss or gain of genetic material, but an exchange of genetic material
Which type of chromosomal abnormality can result in a functionally balanced karyotype with a reduced chromosome number?
Robertsonian translocation
What is the characteristic of a karyotype resulting from a reciprocal translocation between two non-homologous chromosomes?
It has two derivative chromosomes with exchanged genetic material
What is the consequence of a Robertsonian translocation in terms of the genetic material carried by the lost short arms?
The lost short arms do not carry important genetic material
Which type of chromosomal abnormality is always unbalanced?
Isochromosome
What is the karyotype of an offspring with Down syndrome resulting from a Robertsonian translocation?
46,XY,-14,+rob(14q21q)
What is the main difference between reciprocal translocation and inversion?
Reciprocal translocation involves two non-homologous chromosomes, while inversion involves a single chromosome
What is the consequence of a reciprocal translocation in terms of the genetic material carried by the derivative chromosomes?
The derivative chromosomes carry genetic material from two non-homologous chromosomes
What is the characteristic of a carrier with a balanced reciprocal translocation?
They are always normal and healthy
Which type of chromosomal abnormality can result in a Down syndrome, but is not a Robertsonian translocation?
Trisomy 21
Study Notes
Translocation
- Involves exchange of genetic material between two chromosomes, with two types: Reciprocal translocation and Robertsonian translocation (centric fusion)
Reciprocal Translocation
- No loss of genetic material, but an exchange of genetic material between two non-homologous chromosomes to form two derivative chromosomes
- Example: balanced reciprocal translocation between a chromosome 3 and a chromosome 17, with a G-banding karyotype of 46, XX, t (3q;17q)
Robertsonian Translocation (Centric Fusion)
- Results from break at or near the centromere in two acrocentric chromosomes (D/D, D/G, G/G) and subsequent fusion of their long arms
- The fragment formed by fusion of their short arms is lost
- Functionally balanced translocation, although chromosome number is reduced to 45
- Carriers are normal because the two short arms that are lost do not carry important genetic material
- Example: Normal carrier with a G-banding karyotype of 45,XX,-14,-21,+t(14q21q)
Production of Down Syndrome
- A normal carrier of Robertsonian translocation can produce Down syndrome
- Example: G-banding karyotype of 46,XY,-14,+rob(14q21q) (Down Syndrome)
Types of Structural Abnormalities
- Deletions, ring chromosomes, and isochromosomes are always unbalanced
- Inversions, insertion, reciprocal translocations, and Robertsonian translocations may be balanced or unbalanced
Karyotype Nomenclature
- Normal female or male: 46, XX or 46,XY
- Plus (+) or minus (-) sign followed by a number indicates an extra or missing entire chromosome: e.g. 47,XX,+21 or 45, XX, -15
- When a piece of a chromosome is missing, the chromosome number is indicated followed by a 'p' or 'q' and a minus (-) sign: e.g. 5p-
- Other notations include 'del' (deletion), 'dup' (duplication), 'inv' (inversion), 'ins' (insertion), 's' (satellite), 'rob' (Robertsonian translocation), and 't' (translocation)
Translocation
- Involves exchange of genetic material between two chromosomes, with two types: Reciprocal translocation and Robertsonian translocation (centric fusion)
Reciprocal Translocation
- No loss of genetic material, but an exchange of genetic material between two non-homologous chromosomes to form two derivative chromosomes
- Example: balanced reciprocal translocation between a chromosome 3 and a chromosome 17, with a G-banding karyotype of 46, XX, t (3q;17q)
Robertsonian Translocation (Centric Fusion)
- Results from break at or near the centromere in two acrocentric chromosomes (D/D, D/G, G/G) and subsequent fusion of their long arms
- The fragment formed by fusion of their short arms is lost
- Functionally balanced translocation, although chromosome number is reduced to 45
- Carriers are normal because the two short arms that are lost do not carry important genetic material
- Example: Normal carrier with a G-banding karyotype of 45,XX,-14,-21,+t(14q21q)
Production of Down Syndrome
- A normal carrier of Robertsonian translocation can produce Down syndrome
- Example: G-banding karyotype of 46,XY,-14,+rob(14q21q) (Down Syndrome)
Types of Structural Abnormalities
- Deletions, ring chromosomes, and isochromosomes are always unbalanced
- Inversions, insertion, reciprocal translocations, and Robertsonian translocations may be balanced or unbalanced
Karyotype Nomenclature
- Normal female or male: 46, XX or 46,XY
- Plus (+) or minus (-) sign followed by a number indicates an extra or missing entire chromosome: e.g. 47,XX,+21 or 45, XX, -15
- When a piece of a chromosome is missing, the chromosome number is indicated followed by a 'p' or 'q' and a minus (-) sign: e.g. 5p-
- Other notations include 'del' (deletion), 'dup' (duplication), 'inv' (inversion), 'ins' (insertion), 's' (satellite), 'rob' (Robertsonian translocation), and 't' (translocation)
Translocation
- Involves exchange of genetic material between two chromosomes, with two types: Reciprocal translocation and Robertsonian translocation (centric fusion)
Reciprocal Translocation
- No loss of genetic material, but an exchange of genetic material between two non-homologous chromosomes to form two derivative chromosomes
- Example: balanced reciprocal translocation between a chromosome 3 and a chromosome 17, with a G-banding karyotype of 46, XX, t (3q;17q)
Robertsonian Translocation (Centric Fusion)
- Results from break at or near the centromere in two acrocentric chromosomes (D/D, D/G, G/G) and subsequent fusion of their long arms
- The fragment formed by fusion of their short arms is lost
- Functionally balanced translocation, although chromosome number is reduced to 45
- Carriers are normal because the two short arms that are lost do not carry important genetic material
- Example: Normal carrier with a G-banding karyotype of 45,XX,-14,-21,+t(14q21q)
Production of Down Syndrome
- A normal carrier of Robertsonian translocation can produce Down syndrome
- Example: G-banding karyotype of 46,XY,-14,+rob(14q21q) (Down Syndrome)
Types of Structural Abnormalities
- Deletions, ring chromosomes, and isochromosomes are always unbalanced
- Inversions, insertion, reciprocal translocations, and Robertsonian translocations may be balanced or unbalanced
Karyotype Nomenclature
- Normal female or male: 46, XX or 46,XY
- Plus (+) or minus (-) sign followed by a number indicates an extra or missing entire chromosome: e.g. 47,XX,+21 or 45, XX, -15
- When a piece of a chromosome is missing, the chromosome number is indicated followed by a 'p' or 'q' and a minus (-) sign: e.g. 5p-
- Other notations include 'del' (deletion), 'dup' (duplication), 'inv' (inversion), 'ins' (insertion), 's' (satellite), 'rob' (Robertsonian translocation), and 't' (translocation)
Learn about the two types of chromosomal translocation, reciprocal and Robertsonian, and how they affect genetic material. Understand the differences between these translocations and their effects on chromosomes.
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