Mutations Dr. Evil: I have one simple request. And that is to have sharks with frickin' laser beams attached to their frickin’ heads!... What do we have?

MutationsMutations

Dr. Evil: I have one simple request. And that is to have sharks with frickin' laser beams attached to their frickin’ heads! . . . What do we have?

Number Two: Sea bass.

Dr. Evil: . . . Rrrriiight.

Number Two: They're mutated sea bass.

Dr. Evil: I have one simple request. And that is to have sharks with frickin' laser beams attached to their frickin’ heads! . . . What do we have?

Number Two: Sea bass.

Dr. Evil: . . . Rrrriiight.

Number Two: They're mutated sea bass.

MutationsMutations

• Changes in the DNA occasionally occur. • Almost always harmful, but VERY

occasionally code for a new, good, protein/trait.

• Methods to protect DNA from changes are constantly active.

• Changes in the DNA occasionally occur. • Almost always harmful, but VERY

occasionally code for a new, good, protein/trait.

• Methods to protect DNA from changes are constantly active.

Types of MutationsTypes of Mutations

• A point or substitution mutation is a change in a single base pair in DNA.

• A point or substitution mutation is a change in a single base pair in DNA.

Normal

Point mutation

mRNA

ProteinStop

Stop

mRNA

Protein

Replace G with A

The effects of point mutationsThe effects of point mutations

• CAN change the amino acid that the codon codes for. Sometimes not. (Why not?)

• A single wrong amino acid can affect the shape of the protein.

• CAN change the amino acid that the codon codes for. Sometimes not. (Why not?)

• A single wrong amino acid can affect the shape of the protein.

Frameshift mutationsFrameshift mutations

• Deletion– A single base lost in DNA.– mRNA would be out of position by one base.– Every codon after the deleted base would be

different and thus different amino acids.

• Deletion– A single base lost in DNA.– mRNA would be out of position by one base.– Every codon after the deleted base would be

different and thus different amino acids.

mRNA

Protein

Frameshift mutation

Deletion of U

Frameshift mutationsFrameshift mutations

• Insertion• Same thing as deletion

- every amino acid after insertion would be different.

• Frameshift mutation because it shifts the reading of codons by one base.

• Insertion• Same thing as deletion

- every amino acid after insertion would be different.

• Frameshift mutation because it shifts the reading of codons by one base.

Causes of MutationsCauses of Mutations

• Just happen, spontaneous mistake.• Caused by something else.

– Mutagens cause changes in DNA.– Radiation

• X rays, cosmic rays, ultraviolet light, nuclear radiation• Cause deletions

– Chemicals• Dioxins, asbestos, benzene, formaldehyde (gasoline, old

insulation, refrigerants, preservatives)• Cause Point or Substitution mutations

– High temperatures.

• Just happen, spontaneous mistake.• Caused by something else.

– Mutagens cause changes in DNA.– Radiation

• X rays, cosmic rays, ultraviolet light, nuclear radiation• Cause deletions

– Chemicals• Dioxins, asbestos, benzene, formaldehyde (gasoline, old

insulation, refrigerants, preservatives)• Cause Point or Substitution mutations

– High temperatures.

Repairing DNARepairing DNA

• Enzymes proofread DNA, replace incorrect nucleotides.– Not perfect.– Greater the exposure to a

mutagen the more likely a mistake will not be corrected.

• Enzymes proofread DNA, replace incorrect nucleotides.– Not perfect.– Greater the exposure to a

mutagen the more likely a mistake will not be corrected.

Mutations in body cellsMutations in body cells

• Damage not passed on to offspring.

• May cause problems for the individual.– Impair the function of the cell– Cell divides, new cells also

will have mutation– Could affect genes that

control cell division = cancer.

• Damage not passed on to offspring.

• May cause problems for the individual.– Impair the function of the cell– Cell divides, new cells also

will have mutation– Could affect genes that

control cell division = cancer.

Mutations in reproductive cellsMutations in reproductive cells

• Mutation in a sperm or an egg cell.

• Offspring affected.– New beneficial protein/trait

(VERY rare)– Defective protein– Nonfunctional protein -

embryo death

• Mutation in a sperm or an egg cell.

• Offspring affected.– New beneficial protein/trait

(VERY rare)– Defective protein– Nonfunctional protein -

embryo death

Chromosomal AlterationsChromosomal Alterations

• Changes may occur in chromosomes too.• Called chromosomal mutations.• Common in plants.• Few passed on, zygote usually dies.

• Changes may occur in chromosomes too.• Called chromosomal mutations.• Common in plants.• Few passed on, zygote usually dies.

Chromosomal AlterationsChromosomal Alterations

• Part of a chromosome is left out.• Part of a chromosome is left out.

Deletion

A B C D E F G H A B C E F G H

• Part of a chromatid breaks off and attaches to its sister chromatid.

• Part of a chromatid breaks off and attaches to its sister chromatid.

Insertion

A B C D E F G H A B C B C D E F G H

Chromosomal AlterationsChromosomal Alterations

• Part of one chromosome breaks off and is added to a different chromosome, a translocation occurs.

• Part of one chromosome breaks off and is added to a different chromosome, a translocation occurs.

A B E FDCBX AWC HGGE HD F

W X Y Z Y ZTranslocation

Any change in DNA sequences is called a _______.

Question 1

D. translation

C. transcription

B. mutation

A. replication

The answer is B.

Which is more serious, a point mutation or a frameshift mutation? Why?

Question 2

Answer

A frameshift mutation is more serious than a point mutation because it disrupts more codons than a point mutation.

Why are chromosomal mutations rarely passed on to the next generation?

Question 3

Answer

Few chromosomal changes are passed on to the next generation because the zygote usually dies. If the zygote survives, it is often sterile and incapable of producing offspring.

Question 10The DNA sequences of a parrot _________.

D. contain exactly the same nucleotides as those of a beetle

C. are exactly the same as those of a human

B. are more similar to a fern than a dog

A. are more similar to those of a clam than a robin

The answer is D.