Chromosomal aberrations are disruptions in the normal chromosomal content of a cell.
In other words, they are changes in the number and or arrangement of genes in the chromosomes.
2. INTRODUCTION
The word ‘Chromosome’ is derived from Greek
word “chroma”-color and “soma”- body .
Normally in males we have 44+xy and in female we
have 44+xx chromosomes
A female ova consists of 23 chromosomes and sperm
consists of 23 chromosomes so after fertilization a
zygote comprises of 46 chromosomes(23 pairs)
4. DEFINITION
Chromosomal aberrations are disruptions in the
normal chromosomal content of a cell.
In other words, they are changes in the number and
or arrangement of genes in the chromosomes.
5. ETIOLOGY
Meiosis-if there is an error in cell division,
the egg or sperm can end up with too many or
not enough chromosomes.
Mitosis- if the chromosome do not split into
equal halves, the new cells can have an extra
chromosome or have a missing chromosome.
6. ETIOLOGY
Maternal age- eggs are also aging and may have the
incorrect number of chromosomes at the time of fertlization.
Consanguinity- it describes a relationship between two
people who share a common ancestor or a shared blood
relationship .
Radiations- it is teratogenic
Environment- it may include medications, foods, etc.
9. MONOSOMY
In this one chromosome is missing.
When a chromosome does not separate properly
during meiosis I or II it is called as meiotic
nondisjunction.
It is incompatible with survival because of loss of
too much genetic information.
12. TRISOMY
3 instances of a particular chromosome are
present instead of normal 2 chromosomes.
Occurs if the chromosomes fail to separate
properly during cell division.
15. TETRASOMY
It Is a deviation of an abnormal number of
chromosomes in which an additional
chromosomal pair is added to particular
chromosome(2n+2).
A cell contain 48 chromosomes here.
17. TRIPLOIDY
There is a complete set of extra chromosomes.
It can be due to:
a. Egg is fertilized by a sperm with a double set of
chromosomes.
b. The egg is fertilized by two sperms.
c. The egg producing cells fail to divide properly
and so the mature egg contains a double set of
chromosomes.
22. DELETION
It means of loss of small portion of chromosome
occurs from breakage at random in both
chromatids of a chromosome(chromosome
break), or only in one chromatid (chromatid
break).
24. TRANSLOCATION
Sometimes a segment of a chromosome becomes
detached and unites with another non- homologous
chromosome.
It is of two types:
i. Simple translocation
ii. Reciprocal translocation
27. INSERTION
A fragment is transferred from a chromosome to a
non homologous chromosome.
It is a rare non reciprocal type of translocation
which involves three breaks.
29. INVERSION
It results when there are two breaks in a
chromosome and the detached segment becomes
reinserted in the reverse order.
It is of two types depending upon inclusion or
absence of centromere.
30. A. Paracentric- both breaks in one arm of
chromosome
B. Pericentric- it has breakpoints on either side of
the centromere.
32. ISOCHROMOSOME
It is a chromosome that has lost one of its arm and
replaced it with an exact copy of the other arm.
33.
34. RING CHROMOSOME
It was first discovered by Lilian Vaughan in 1926.
It is a chromosome whose arms have fused
together to form a ring.
It is denoted by symbol ‘r’ in human genetics.
36. DUPLICATION
The term "duplication" simply means that a part of a
chromosome is duplicated, or present in two copies.
This results in having extra genetic material, even
though the total number of chromosomes is usually
normal.
Since a very small piece of a chromosome can contain
many different genes, the extra genes present in a
duplication may cause those genes to not function
properly
37. DUPLICATION
These "extra instructions" can lead to errors
in the development of a baby.
One example of a genetic syndrome caused
by a duplication is called "Pallister Killian
syndrome," where part of the #12
chromosome is duplicated.