mutation

gene mutation/
point mutation

definition

changes in the nucleotide base
pairs in a gene

due

mistake in base pairing during DNA replication

result

changes of codon in mRNA. Hence, change the amino acid sequence and the protein.Different protein produced may not function as normal

type

base substitution

one nucleotide pair is replaced with
another nucleotide pair in the
DNA sequence

lead- silent, missense, nonsense mutation

SILENT MUTATION

base substitution nucleotide pair of DNA
has no effect on the encoded protein

change in nucleotide but translated
same amino acid

changes codon on mRNA
codes for the same amino acid

MISSENSE MUTATION

cause frameshift mutation

amino acid changes to another
amino acid

results in ONE WRONG CODON
and ONE WRONG AMINO ACID
in polypeptide

less active protein

eg: SICKLE CELL
ANEMIA(RBC shape
like a crescent)

DNA- CTT replaced CAT
mRna-codon GAA replaced GUA
polypeptide- glutamic acid replaced valine

symptoms sickle
cell anemia

*Hb-stiff, tend to accumulate at
blood capillary
*fatal form of anemia
*organ damages
*physical weakness

NONSENSE MUTATION

changes mRNA into
a stop codon

translation terminated
produce shorter
polypeptide

lead to non-functional proteins

base insertion

Addition of one or a more nucleotide pair
into the DNA

frameshift mutation

base deletion

Loss of one or more
nucleotide pair from
the DNA

frameshift mutation

base inversion

More than one nucleotide
breaks, rotate 180 and
reattached to the DNA

chromosomal mutation

Definition

changes in chromosomal structure or chromosomal number

type

CHRMOSOMAL NUMBER
ALTERATIONS
change in number

EUPLOIDY/POLYPOIDY

has more than two sets of chromosomes
(more common in plant)

3n,4n,5n,

occur naturally(by non-disjunction or induction)

form new species better qualities

type

autoploidy

individual has more than two
chromosomes sets that all derived from
same species

alloploidy

individual has more than two
chromosomes sets that derived from
different species

ANEUPLOIDY

chromosomal EXTRA or MISSING from
normal set

cause-non-disjunction during meiosis
(anaphaseI,II)

non-disjunction-failure of a homologous chromosomes
or sister chromatid to separate and move to opposite poles

occur in autosome and sex-chromosomes

eg: 2n-1monosomy,2n+1trisomy

CHROMOSOMAL ABERRATION
change in structure