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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| Types of chromosomal mutations |
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