CHANGES IN THE CHANGES IN THE GENETIC CODEGENETIC CODE

EctrodactylyEctrodactyly

What do they all have in common?What do they all have in common?

They’re all mutations!They’re all mutations!

MUTATIONSMUTATIONS

a change in the DNA codea change in the DNA code

causes a different (sometimes causes a different (sometimes wrong) type of protein to be madewrong) type of protein to be made

may or may not be good for the may or may not be good for the organismorganism

ALONG THE WAYALONG THE WAY

good changes occurgood changes occur

bad changes occurbad changes occur

changes that don’t matter either waychanges that don’t matter either way

CHANGE IS NECESSARYCHANGE IS NECESSARY

without changes we would all look alikewithout changes we would all look alike

without changes we would not evolvewithout changes we would not evolve

without changes we would not develop without changes we would not develop immunities to diseaseimmunities to disease

SO… Is change/variation a good SO… Is change/variation a good thing???thing???

YES!YES!

Causes of VariationCauses of Variation

Crossing OverCrossing OverMutationsMutations– Some happen randomly Some happen randomly – Some caused by Mutagens (agents that Some caused by Mutagens (agents that

cause mutations)cause mutations)Nuclear RadiationNuclear RadiationUltraviolet LightUltraviolet LightX RaysX Rayshttp://learn.genetics.utah.edu/units/disorders/sloozhttp://learn.genetics.utah.edu/units/disorders/sloozeworm/mutationbg.cfmeworm/mutationbg.cfm

CROSSING OVERCROSSING OVER

occurs when homologous occurs when homologous chromosomes trade segmentschromosomes trade segments

occurs during Prophase I of Meiosis occurs during Prophase I of Meiosis

entire gene is switchedentire gene is switched

involves the variation of a single traitinvolves the variation of a single trait– gene for big ears exchanges with gene for big ears exchanges with

gene for small earsgene for small ears

AdvantagesAdvantages

variation of offspring from parentsvariation of offspring from parents

allows for “good” changesallows for “good” changes

Better chance of passing on genes Better chance of passing on genes for survivalfor survival

3 TYPES OF MUTATIONS3 TYPES OF MUTATIONS

Chromosomal mutationsChromosomal mutations

Gene mutationsGene mutations

Somatic mutationsSomatic mutations– these usually occur during mitosis and these usually occur during mitosis and

involve a chromosomal mutationinvolve a chromosomal mutation– involved with body cells, not sex cellsinvolved with body cells, not sex cells– tumors are the result tumors are the result

Research your mutationResearch your mutation

1. Answer these questions1. Answer these questions– What does the name of the mutation mean?What does the name of the mutation mean?– What happens to the chromosome?What happens to the chromosome?– What is an example?What is an example?

CHROMOSOMAL CHROMOSOMAL MUTATIONSMUTATIONSNONDISJUNCTIONNONDISJUNCTION

DELETIONDELETION

INVERSIONINVERSION

DUPLICATIONDUPLICATION

TRANSLOCATIONTRANSLOCATION

INSERTIONINSERTION

NONDISJUNCTIONNONDISJUNCTION

failure of homologous pairs to failure of homologous pairs to separate during meiosisseparate during meiosis

correct number of chromosomes are correct number of chromosomes are not present in the gametenot present in the gamete

after fertilization, diploid number is after fertilization, diploid number is not restorednot restored

ExamplesExamples

Trisomy 21(Down Syndrome)- 3 Trisomy 21(Down Syndrome)- 3 copies of chromosome 21copies of chromosome 21

Klinefelters Syndrome- XXYKlinefelters Syndrome- XXY

Turner Syndrome- XTurner Syndrome- X

““Supermales” - XYYSupermales” - XYY

DELETIONDELETION

A SEGMENT OF A CHROMOSOME IS DELETED

ExamplesExamples

Cri-du-chat syndrome- “cry of the Cri-du-chat syndrome- “cry of the cat”- deletion of piece of cat”- deletion of piece of chromosome #5chromosome #5

Angelman Syndrome- deletion of Angelman Syndrome- deletion of piece of chromosome #15piece of chromosome #15

Prader-Willi Syndrome- deletion of Prader-Willi Syndrome- deletion of piece of chromosome #15piece of chromosome #15

INVERSIONINVERSION

A SEGMENT OF THE CHROMOSOME IS FLIPPED IN THE OPPOSITE DIRECTION

DUPLICATIONDUPLICATION

A SEGMENT OF THE CHROMOSOME IS COPIED TWICE

TRANSLOCATIONTRANSLOCATION

SEGMENTS FROM TWO DIFFERENT CHROMOSOMES ARE SWITCHED

ExampleExample

Translocation Down SyndromeTranslocation Down Syndrome

Instead of being 3 separate copies of Instead of being 3 separate copies of chromosome 21, the extra copy is chromosome 21, the extra copy is actually attached to another actually attached to another chromosomechromosome

INSERTION

A SEGMENT OF ONE CHROMOSOME IS INSERTED INTO A DIFFERENT CHROMOSOME

GENE MUTATIONSGENE MUTATIONS

POINT MUTATIONSPOINT MUTATIONS

FRAME SHIFTFRAME SHIFT– insertionsinsertions– deletionsdeletions

INVERSIONSINVERSIONS

LETS MUTATE!LETS MUTATE!

Start with an original strand of DNAStart with an original strand of DNA

GCC TTA CGT TTA CGA CTG TAC GTAGCC TTA CGT TTA CGA CTG TAC GTA

CGG CGG AATAAT GCAGCA AATAAT GCTGCT GAC ATG CAT GAC ATG CAT

A B C DA B C D

lets assume this strand codes for a lets assume this strand codes for a proteinprotein

AMINO ACIDS

POINT MUTATIONSPOINT MUTATIONS

TTA CGT TTA CGATTA CGT TTA CGA

AAT AAT GCAGCA AAT GCT AAT GCT ORIGINALORIGINAL

1 base is replaced with another base1 base is replaced with another base

TTA CTTA CTTT TTA CGAT TTA CGA

AAT AAT GGAAAA AAT GCT AAT GCT MUTATIONMUTATION

B

E

ExampleExample

Sickle Cell Anemia- changing 1 base Sickle Cell Anemia- changing 1 base causes mutation that codes for valine causes mutation that codes for valine instead of glutamate in the protein instead of glutamate in the protein hemoglobinhemoglobin

Individuals produce different type of Individuals produce different type of hemoglobinhemoglobin

Red Blood Cells become sickle shaped and Red Blood Cells become sickle shaped and don’t pass thru blood vessels as easilydon’t pass thru blood vessels as easily

Cells die sooner than normalCells die sooner than normal

Individuals don’t get as much oxygenIndividuals don’t get as much oxygen

http://www.montgomerycollege.edu/~wolehttp://www.montgomerycollege.edu/~wolexik/Sickle%20Cell%20Anemia%20400x.jpxik/Sickle%20Cell%20Anemia%20400x.jpgg

FRAME SHIFTSFRAME SHIFTS

TTA CGT TTA CGATTA CGT TTA CGAAATAAT GCAGCA AATAAT GCTGCT ORIGINALORIGINAL A B C DA B C D

TTA CGT TTA TTA CGT TTA AACG ACG AAATAAT GCAGCA AATAAT TTGCGC T TINSERTION-base is INSERTION-base is

insertedinserted A B C FA B C F

TTA CGT TTA CGT TACTAC GA GAAATAAT GCAGCA ATGATG CT CT DELETION- base is DELETION- base is

deleteddeleted A B G A B G

INVERSIONSINVERSIONS

TTA CGT TTA CGATTA CGT TTA CGA

AATAAT GCAGCA AATAAT GCTGCT ORIGINALORIGINAL A B C DA B C D

Codon is found in reverse orderCodon is found in reverse order

TTA TTA TGCTGC TTA CGA TTA CGA

AATAAT ACGACG AATAAT GCTGCT INVERSIONINVERSION A H C DA H C D

ConsequencesConsequences

Sometimes mutations are bad and Sometimes mutations are bad and cause for different proteins to be cause for different proteins to be mademadeBut- if you look at the amino acid But- if you look at the amino acid chart- several different codons code chart- several different codons code for the same amino acidsfor the same amino acidsMutations can occur but wouldn’t be Mutations can occur but wouldn’t be noticednoticedSome mutations are masked by other Some mutations are masked by other genesgenes