basic bsc nursing mutation topic in genetics

1. MUTATIONS

2. Definition
◦ A mutation is defined as a permanent change in the genetic
material ( DNA) which results in a disease
Causes
◦ Spontaneous mutation: majority of mutations occurs
spontaneously due to errors in DNA replication and repair.
◦ Induced mutation: mutations can be caused due to exposure to
mutagenic agents kike chemicals , viruses and ultraviolet or
ionizing radiations

3. Classification of mutations
Depending on the cell involved
Germ cell mutations: mutations that affect the germ cells are transmitted to the progeny
descendants and can give rise to inherited diseases.
Somatic cell mutations: mutations involving the somatic cells can produce cancers and some
congenital malformations. These mutations are not inherited and are known as de novo mutations.
Depending on the nature:
Numerical mutation: There is either gain or loss of whole chromosome . These usually develop
during gametogenesis and are known as genomic mutations.
Structural chromosomal mutations: The rearrangement of genetic material causes structural
change. Structural mutations may be visible during karyotyping or submicroscopic. The
submicroscopic gene mutations can result in partial or complete deletion of a gene or more often a
single nucleotide base.

4.  Point mutation: when a nucleotide base is replaced by a different nucleotide base within a gene.
 Frame shift mutation: This is due to insertion or deletion of one or more nucleotides.
 Trinucleotide repeat mutation: The DNA contains several repeat sequence of three nucleotide. when
they are repeated directly adjacent to each other they are known as tandem repeats. When the repetitive
trinucleotides sequences reach above a particular threshold, they can expand or contract.
 Depending on functional effect
Mutations in DNA can lead to either change in the amino acid sequence of a specific protein or may
interfere with its synthesis. The consequences vary from those without any functional effect to those which
have serious effects.
 Loss of function mutation: These mutations cause reduction or loss of protein function.
 Gain of function mutation: protein function is altered in such a manner that result in change of original
function.
 Lethal mutation: These leads to death of fetus.