Translocation introduction and characteristics Types of translocation Mechanism of reciprocal translocation

1. TRANSLOCATION
TRANSLOCATION
TRANSLOCATION
Submitted by:
Muskan Singhal
M.Sc Biotechnology
1st year ( II Sem)
Chaudhary Charan Singh
University
Submitted To:
Dr. Gyanika Shukla

2. When two non- homologous chromosomes exchange their
parts , the resulting chromosomal rearrangement are
translocations.
The reason behind translocation is that if the cell are exposed
to agents that cause chromosomes to break and broken ends
lack teleomeres.
These reactive ends are join by Dna repair enzymes . If multiple
chromosomes are broken then reactive ends may be joined
incorrectly to produce abnormal chromosome.
This is one mechanism that can cause reciprocal translocation
to occur
A second mechanism that can cause a translocation is an
abnormal crossover. This also results in reciprocal
translocation.
Translocation in humans is linked with many disorders such as
mental retardation, infertility, and cancer.
Introduction

3. Chromosomal translocation is a result of unusual
rearrangement of chromosomes.
It is involved in the generation of a novelchromosome.
It alters the size of the chromosome as well as the position
of the centromere.
Translocation requires the break downing of double-strand
DNAs at two different places.
It occurs many times during the evolution of species and
provides help in the identification of closely related species.
CHARACTERISTICS

4. TYPES OF
TRANSLOCATION

5. A reciprocal translocation can be produced
when two non homologous chromosomes cross
over. This type of rare aberrant event results in
a rearrangement of the genetic material,
though not a change in total amount of genetic
material.
Reciprocal Translocation

6. How reciprocal translocation arises?
During meiosis, the homologous chromosomes attempt
to synapse with each other.
For these translocated chromosomes, the expected
segregation pattern is governed by the centromeres.
Each haploid gamete should receive one centromere
located on chromosome I and one centromere located
on chromosome 2. This can occur in two ways.
One possibility is alternate segregation. this occurs
when the chromosomes diagonal to each other within
the translocation cross sort into the same cell. One
daughter cell receives two normal chromosomes, and
the other cell gets two translocated chromosomes.
Following meiosis II, four haploid cells are produced:
two have normal chro- mosomes, and two have
reciprocal (balanced) translocations.

7. On very rare occasions, adjacent-2 segregation can occur. In this case, the
centromeres do not segregate as they should. One daughter cell has received
both copies of the centromere on chromosome 1; the other, both copies of the
centromere on chromosome 2. This rare segregation pattern also yields four
abnormal haploid cells that contain an unbalanced combination of
chromosomes.
Alternate and adjacent-1 segregation patterns are the likely outcomes when
an individual carries a reciprocal translocation. Depending on the sizes of the
translocated segments, both types may be equally likely to occur. In many
cases, the haploid cells from adjacent-1 segregation are not viable, thereby
lowering the fertility of the parent. This condition is called semisterility.

8. Robertsonian Translocation, named after William Robertson , who first
described this type of fusion in grasshoppers.
This type of translocation arises from breaks near the centeromeres of two non
homologous acrocenteric chromosomes.
Forexample , The long arms of chromosomes 14 and 21 had fused creating one
large single chromosome, the two short arms are lost
Robertsoniantranslocation involves only the acrocentric chromosomes
13,14,15,21,22.
Itis also known as centeric fusion type . Frequency = 1/1000 livebirths
Chromosome 13 translocate with chromosome 21
Chromosome 14 translocate with chromosome 21
Chromosome 15 translocate with chromosome 21
Chromosome 21 translocate with chromosome 22
Robertsonian Translocation

9. Robertsonian translocation

10. Translocation further classified as balanced and unbalanced
translocation. In balance translocation, the total amount of genetic
material is not altered . Like inversions , balanced translocation usually
occur without any phenotypic consequences because the individual has
a normal amount of genetic material . In unbalanced translocation, in
which significant portions of genetic material are duplicated and deleted
. Unbalanced translocation are generally associated with phenotypic
abnormalities or even lethality.
Example: Transmission of familial Down Syndrome
Balanced and Unbalanced Translocation

12. It is one directional transfer of chromosomal
segment to another chromosome. Furthermore
this may drastically alter the chromosome size
and position of its centromere.
Only one chromosomal segment takes part in
the translocation.
One chromosomal segment moves one to
another locus of a non homologous
chromosomes.
Nonreciprocal translocation

13. GENETICS: ANALYSIS AND PRINCIPLES,
Third Edition by Robert J .Brooker.
https://www.researchgate.net/publication
/344224726
www.wikipedia.com
References