Point Mutations

Presented by:

Muzhar Ali 4028

Ali raza 4029

Presented To:

DR.M.Javed Iqbal

Siddiqui

¤ Introduction of mutations¤ Types of mutations¤ Chromosomal mutation ¤ Point mutation¤ Types of point mutations¤ Causes of mutations

Contents

What Are Mutations?

• Changes in the nucleotide sequence of DNA

• May occur in somatic cells (aren’t passed to offspring)

• May occur in gametes (eggs & sperm) and be passed to offspring

Types of Mutations

Chromosome Mutations

• May Involve:• Changing in the number of

chromosomes Lose or se gain of chromosomes e.g.

• Down’s syndrome .• Change in the structure of

chromosomes

– gfgfgfggfgfgfgfghgfgvggfff

Chromosome Mutations

• Down Syndrome– Chromosome 21 does not separate

correctly.– They have 47 chromosomes in

stead of 46.– Children with Down Syndrome

develop slower, may have heart and stomach illnesses and vary greatly in their degree of inteligence.

Chromosome Mutations

• Due to change in structure.–Deletion–Inversion–Translocation–Nondisjunction–Duplication

Chromosome Mutation Animation

Point Mutation

• Change of a single nucleotide• Includes the deletion,

insertion, or substitution of ONE nucleotide in a gene

–Point Mutations– Base Substitution–Silent mutation– Sense mutation –Nonsense mutation

Mutations: SubstitutionsSubstitution mutation

GGTCACCTCACGCCA ↓

CCAGUGGAGUGCGGU

↓Pro-Arg-Glu-Cys-Gly

Substitutions will only affect a single codonTheir effects may not be serious unless they affect an amino acid that is essential for the structure and function of the finished protein molecule (e.g. sickle cell anaemia)

Normal geneGGTCTCCTCACGCCA

↓CCAGAGGAGUGCGGU

Codons ↓

Pro-Glu-Glu-Cys-GlyAmino acids

© 2010 Paul Billiet ODWS

Point Mutations • Silent mutation = no change to protein

AUGCGUGUAUACGCAUGCGAGUGA

MetArgValTyrAlaCysGluStop

AUGCGUGUAUACGCUUGCGAGUGA

MetArgValTyrAlaCysGluStop

Point Mutation

• Sickle Cell disease is the result of one nucleotide substitution• Occurs in the

hemoglobin gene

Fig 4.4

Point Mutations • Missense mutation = changes amino acid

AUGCGUGUAUACGCAUGCGAGUGA

MetArgValTyrAlaCysGluStop

AUGCGUGUAUACGUAUGCGAGUGA

MetArgValTyrValCysGluStop

Sickle cell anemia• Hemoglobin protein in red blood cells– strikes 1 out of 400 African Americans– limits activity, painful & may die young

Normalround cells

Misshapensickle cells

Only 1 out of146 amino acids

Point Mutations • Nonsense mutation = change to STOP

AUGCGUGUAUACGCAUGCGAGUGA

MetArgValTyrAlaCysGluStop

AUGCGUGUAUAAGCAUGCGAGUGA

MetArgValStop

Really destroyedthat protein!

Frameshift Mutations • Add or delete one or more bases– changes the meaning of the whole protein

THEFATCATANDTHEREDRATRAN

THEFATCANTANDTHEREDRATRAN

THEFATCAANDTHEREDRATRANOR

Add one!Delete one!

Does this changethe sentence?A LOT!

Frameshift Mutations • Addition = add one or more bases

AUGCGUGUAUACGCAUGCGAGUGA

MetArgValTyrAlaCysGluStop

AUGCGUGUAUACGUCAUGCGAGUGA

MetArgValTyrValMetArgValA

Frameshift Mutations • Deletion = lose one or more bases

AUGCGUGUAUACGCAUGCGAGUGA

MetArgValTyrAlaCysGluStop

AUGCGUGUAUACGAUGCGAGUGA

MetArgValTyrAspAlaSerGA

Gene Mutation Animation

Causes of Mutations

• Chemical cause the mutations are called Mutagens. like

• Ionizing radiation• Alpha, beta, gamma and cosmic rays.• Nonionizing radiation• Uv light,• Chemical mutagens• Nitrous acid, Hydroxylamine

Example of chemical mutations

02/05/2023 Mrs Smith: Ch13: Mutations an Chromosomal Abnormalities 31