Mutation Flashcards
a permanent change in the DNA
sequence that makes up a gene.
• ____ range in size from one DNA base to a
whole chromosome change.
Mutation
Gene mutations occur in two ways:
inherited from a parent
occur in the
DNA of individual cells
mutations can be grouped according to
• their sizes,
• phenotypic effects,
•the cause of occurrence
•the type of cell in which they occur
Types of chromosomal abnormalities
poliploidy:
triploidy, tetraploidy - aneuploidy: trisomy,
monosomy
Numerical abnormalities
Types of chromosomal abnormalities
translocation, deletion, inversion,
duplication, ring, marker
Structural
A type of chromosome rearrangement
involving the exchange of chromosome segments between two
chromosomes that do not belong to the same pair of chromosomes.
Reciprocal Translocation
if there is no gain or loss of chromosomal material
balance
translocation, inversions
if there is gain or loss of chromosomal material
Unbalanced
Duplication
•Deletion
•Insertion
•Ring chromosome
BALANCED
occurs
when the segment
between two breakpoints is
inverted before rejoining
the breaks
Inversion
UNBALANCED
loss of a segment
of the chromosome
Deletion
UNBALANCED
occurs when a
segment of the chromosome is
repeated, once or several
times.
Duplication
UNBALANCED
Two ends of the segment
between breakpoints are joined to form a
circular structure.
Ring chromosome
mutation occurs when a DNA gene is damaged
or changed in such a way as to alter the genetic
message carried by that gene
the cause of occurence
Caused by replication mistakes
spontaneous
Induced by exposure to a variety of
mutagenes
induced
the mutation is not passed along to
the next generation Cancer tumours are a unique
class of somatic mutations.
somatic cells
germ cells give rise to gametes,
some gametes will carry the mutation and it will
be passed on to the next generation.
germinal cells
Typically germinal mutations are ___ expressed in
the individual containing the mutation.
Not
Mutations by size
• Microscopic (macro mutations, chromosomal abnormalities)
it varies from 2000 kb to larger
Mutation by size
• Submicroscopic (micro mutations, gene mutations)
- a single base or
- mutations that are too small not to be evaluated at the
microscope level
Base pair substitution mutations in a nucleotide is
observed as conversion to another nucleotide
replace
one amino acid
with another
in gene product. These
are nonsynonymous
substitutions
occur in coding region and changes the triplet codon for
different amino acid
missense mutations
replace
an amino
acid
codon
with
a
stop codon. Point mutation,
which
converts
the
normal
codon
to UAA, UGA, UAG, creating a premature STOP codon is
called
nonsense mutations
do not change the sequence
of the gene product. Causes a codon change but does not
result in an altered amino acid because of the degenaracy of
the genetic code.
synonymous (silent) mutations
Insertion or deletion of a small number
of nucleotides (different than multiplication of three) into a
coding region, which alter the reading frame of translation
from that point.
frameshift mutation
caused
by
the
expansion of
trinucleotide
repeats
within
the
genome
dynamic mutation
repeat
units
lies within
or adjacent
to
a
diseaseassociated
gene,
there
is a tendency
for
the
tract to
become progressively larger by expansion at meiosis, it
becomes
«unstable» by reaching a certain treshold size
Trinucleoside
the tendency for the severity of a condition in
successive
generations
Anticipation
example of dynamic mutation
Huntington’s disease
an example for repeat
extension
fragile x syndrome
Such mutations cause
protein to be partially (hypomorph) or totally
(amorph) loss of function.
Loss function mutations
Due to such mutations,
the gene product acquires a new, hypermorphic
function.
gain of function mutations
seen in genes with vital
functions.
lethal types of mutations
