Mutations
(in Latin Mutatus means Change) are
permanent changes in genes or chromosomes that can be passed to offspring if
they occur in cells that become gametes. There are two main types of mutations:
Chromosomal Mutations and Gene Mutations.
Chromosomal
Mutations
Chromosomal
mutations are changes that occur in the structure or number of chromosomes.
They can result in significant alterations to an individual's genetic makeup.
There are two main types of chromosomal mutations: changes in chromosome number
and changes in chromosome structure.
Changes in
Chromosome Number
Changes
in chromosome number involve alterations to the total number of chromosomes in
an organism's cells. This can occur due to errors in the process of meiosis,
where chromosomes are supposed to separate evenly. Examples of changes in
chromosome number include monosomy, trisomy, and polyploidy.
Monosomy and Trisomy
Monosomy
occurs when an individual has only one copy of a particular type of chromosome
(2n-1), while trisomy occurs when an individual has three copies of a
particular type of chromosome (2n+1). Monosomy and trisomy are usually caused
by non-disjunction during meiosis, where chromosomes fail to separate properly.
Monosomy and trisomy can occur in both plants and animals. For example, Turner
syndrome in humans is a monosomy of the sex chromosomes, where the individual
inherits only a single X chromosome. Down syndrome, which involves an extra
copy of chromosome 21, is the most common trisomy among humans.
Polyploidy
Polyploidy
refers to the presence of more than two sets of chromosomes in an organism.
Polyploid organisms can be triploid (3n), tetraploid (4n), pentaploid (5n), and
so on. Polyploidy is not seen in animals, but it is estimated that 47% of all
flowering plants are polyploids. Polyploidy is commonly observed in crops such
as wheat, corn, cotton, sugarcane, and fruits such as watermelons, bananas, and
apples. Polyploids generally arise following hybridization, where chromosomes
from different species are combined.
Changes in
Chromosome Structure
Changes
in chromosome structure occur when the arrangement of genetic material within a
chromosome is altered. This can happen due to various environmental factors
such as radiation, certain chemicals, or viral infections, which can cause
chromosomes to break. When the broken ends of chromosomes do not rejoin in the
same pattern as before, it results in changes in chromosomal structure.
Inversion
Inversion
occurs when a segment of a chromosome is turned around 180 degrees. This can
result in rearrangement of genes within the inverted segment, potentially
affecting gene function or regulation.
Translocation
Translocation
is the movement of a chromosome segment from one chromosome to another
non-homologous chromosome. This can result in the fusion of two chromosomes or
the transfer of a segment of genetic material to a different chromosome,
potentially disrupting gene function or regulation.
Deletion
Deletion
occurs when an end of a chromosome breaks off or when two simultaneous breaks
lead to the loss of an internal segment. Deletions can result in the loss of
one or more genes, potentially leading to the loss or alteration of specific
traits. An example of a deletion mutation is cri du chat (cat's cry) syndrome,
where a portion of chromosome 5 is deleted.
Duplication
Duplication
is the doubling of a chromosome segment. This can result in the presence of multiple
copies of a gene or genes, potentially leading to changes in gene dosage or
function.
In conclusion, chromosomal mutations are permanent changes in the structure or number of chromosomes, which can have significant effects on an organism's genetic makeup.
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