Mutations  Hollywood’s images of mutation

Mutations  Actual Mutations in fruit flies

What is a mutation?  A mutation is any change in a cell’s DNA  A mutation can occur in an individual gene - results in a single changed protein - cystic fibrosis a mutation in the protein that makes a type of ion channels in cell membrane - bacterial resistance to antibiotics is an example of a beneficial gene mutation

What is a mutation continued  A mutation can occur in a chromosome - a chromosome contains many genes - chromosomal mutations affect many proteins If a mutation occurs in a sex cell, the mutation will be passed to offspring Examples: Down Syndrome Edward’s Syndrome Cri-du-Chat

What Causes Mutations?  Environment: Can be caused by mutagens- a physical or chemical cause of mutation. Examples: UV light, radiation, drugs, and benzene.  Mutagens are often also carcinogens – anything that causes cancer  Can be natural, random events. - mutations occur in 1/100,000 DNA replications (DNA mistakes)  Mutations do not have to be bad (evolution)

Point Mutations  A single nucleotide is altered. Can change one amino acid in a protein  Milk – Mile  GGACAATCA GGACCATCA proline -valine-serine proline-glycine-serine ***ONLY ONE AMINO ACID CAN BE AFFECTED AS A RESULT OF A POINT MUTATION!** *

Frameshift Mutations  A nucleotide is either inserted or deleted from a gene. -all of the triplets from the point of mutation onward will be changed

Frameshift Mutations Insertion  An insertion occurs when a nucleotide is added to a gene Example: A nucleotide is inserted The fat cat ate the rat The faa tca tat eth era t -the extra nucleotide shifts all of the triplets that follow

Frameshift Mutations Deletions  A deletion occurs when a nucleotide is removed from a gene. Example: A nucleotide is removed The fat cat ate the rat Thf atc ata tet her at

Insertion  GGA-CAA-TCA GCG-ACA-ATC-A proline -valine-serine arginine-cysteine-stop Deletion  GGA-CAA-TCA GGA-AAT-CA proline -valine-serineproline-leucine

DeletionExample: Cri du chat syndrome Due to a deletion of part of the short arm of chromosome 5 Occurrence: 1/50,000 births Crying babies sound like cats; mental disability Death by about 4 years

Chromosome Mutations

KARYOTYPES  Kary = nucleus  Karyotype = chart of metaphase chromosome pairs arranged according to length and location of the centromere  Used to pinpoint unusual chromosome numbers in cells

Nondisjunction  Sometimes during meiosis, the homologous chromosomes fail to separate properly  This can result in two types of chromosomal mutations:  (1) trisomy (have an extra set of chromosomes)  (2) monosomy (missing one set of chromosomes)

XYY Syndrome

Turner’s Syndrome

Down’s Syndrome

Klinefelter syndrome: 47, XXYKlinefelter syndrome: 47, XXY males, sterile, feminine body characteristics. Normal intelligence.

Edward’s syndrome (trisomy 18)Edward’s syndrome (trisomy 18):occurs in 1:6000 or 1:8000 live births; very few survive birth.

Mutations on Chromosomes