mutations: changing dna
DESCRIPTION
Mutations: Changing DNA. SBI4U Biology. Mutation : A change in the DNA sequence that is inherited as the DNA is transmitted through cell division. Changes in number or structure of chromosomes Spontaneous Induced Mutagens = UV, X Rays, other radiation; chemicals; heavy metals. - PowerPoint PPT PresentationTRANSCRIPT
Mutations: Changing DNA
SBI4U Biology
Mutation:
A change in the DNA sequence that is inherited as the DNA is transmitted through cell division.
Changes in number or structure of chromosomes Spontaneous Induced Mutagens = UV, X Rays, other radiation; chemicals; heavy metals
Categorising mutations
1. By effect on structure
2. By consequences on resulting proteins
1. Mutations by effect on structurea) Point mutations
Mutations that occur to a specific base pair in the genome.
b) Chromosomal mutations Mutations that involve large segments of DNA.
Point mutationsSubstitution: One base pair is replaced with another
Point mutations (cont`d)Deletion: One or more base pairs is eliminated from
the DNA sequence
Point mutations (cont`d)Insertion: One or more base pairs is inserted into the
DNA sequence
Frameshift mutationsDeletions and insertions of 1-2 base pairs will result in
a shift in the reading frame. “frameshift mutations”
Deleting or inserting 3 base pairs is not considered a frameshift mutation... why??
Chromosomal mutationsLarge scale changes to chromosomesInversion :The reversal of a segment of DNA within a chromosome.Results from breaking and rejoining (upside down)
Chromosomal mutations (cont`d)
Translocation:A fragment of DNA moves from one part of the genome to another.
Can result in a “fusion protein”
Chromosomal mutations (cont`d)
Gene duplication: Duplication of a coding region of DNA along a chromosome
Results from crossing over of misaligned homologues during meiosis I
Chromosomal mutations (cont`d)
Deletion:Part of a chromosome is deleted and becomes “missing”
Chromosomal mutations (cont`d)Insertion:
The complement of deletion. Part of another chromosome is inserted.
Gross Chromosomal
Gross Chromosomal
Aneuploidy = incorrect number of chromosomes
Trisomy = extra chromosome (2n +1)
Monosomy = missing chromosome (2n -1)
Triploid = 3n, Tetraploid = 4n
Trisomy & Monosomy
2. Mutations by consequence on resulting protein
a) Silent mutationsb) Missense mutationsc) Nonsense mutations
Silent mutationsDoes not result in a change in amino acid sequence
no phenotypic change; no effect on the cell
How?May occur within
an intronRedundancy of
genetic code
ACA and ACU are both codons for threonine
Missense mutationsResults in a change to a codon
The wrong amino acid is incorporatedDoes not necessarily drastically alter protein function
Checkpoint:Can you classify this mutation by its effect on structure?
Nonsense mutationsA codon is converted to a stop codon
truncated protein is produced
Checkpoint:Can you classify this mutation by its effect on structure?
Mutation Examples:
I LOVE HER SO MUCH I COULD MARRY HER.
Silent:I LOVE HER SO MUCH I COULD WED HER.
Missense:I LOVE HER SO MUCH I COULD PUNCH HER.
Mutation Examples:
I LOVE HER SO MUCH I COULD MARRY HER.
Chain Termination:I LOVE HER SO MUCH I COULD.
Nonsense:I LOVE HER SO MUCH I COULD MARY HERE THIRST PINK UTAH MONGOOSE LABEL WINE FLIRT LAVA
LAMP TOOL BARGE MAPLE NOSE HAIR RITZ CRACKER CONSPIRACY GONG SHOPPING SPREE WIT’S END NEVADA WONDERFUL SQUID RICE KANGAROO
CELEBRATE WART…
Mutation Examples:
I LOVE HER SO MUCH I COULD MARRY HER.
Deletion Frameshift:I LOVH ERS OM UCHI C OULDM ARRYH ER
Insertion Framshift:I LOXV EHE RS OMUC H ICOUL DMARR YHE
R
Consolidation
Causes of mutationsInnateSpontaneous: Due to errors in replication
EnvironmentalExposure to mutagenic agents
UV radiation, X rays, chemicals