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
Some genetic disorders can be caused by
mutations
› These mutations can occur within the DNA of a
chromosome or they can occur to the
chromosome its self


(When a portion of the DNA is deleted or
removed from the chromosome)
Example:
› ATCGGCTA
›

CGGCTA
The “AT” fragment was deleted
Original:
the fat cat ate the
wee rat
Deletion:
the fat ate the wee
rat

The sentence is missing a word
› Still readable, however
Original:
Deletion:
ATG CTA CAG GGA
ATG CAG GGA
Original strand: Met-Leu-Glu-Gly
 Mutated strand: Met-Glu-Gly

(When a portion of the chromosome is
duplicated or repeated)
 Example:

› TGACCATG
› TGACCATGTG

The “TG” fragment was duplicated (or
copied) at the end
Original: the fat cat ate the wee rat
Insertion: the fat cat ate the the wee

rat
The sentence is still mostly readable
Original:
Duplication:
ATG CTA CAG GGA
ATG CTA CAG CAG GGA
Original strand:
 Mutated strand:

Met-Leu-Glu-Gly
Met-Leu-Glu-Glu-Gly
(When a portion of the DNA is inverted or
switched around in the chromosome)
 Example:

› GTCATACCGT
› GTTACACCGT

The “CAT” fragment flipped around to
“TAC”
Original: the
Inversion:

fat cat ate the wee rat
the fat tar eew eht eta tac
The sentence is now almost completely
unreadable
Original:
Inversion:
ATG CTA CAG GGA
Original strand:
 Mutated strand:

ATG AGG GAC ATC
Met-Leu-Glu-Gly
Met-Arg-Asp-Iso
(When a portion of the DNA in the
chromosome is replaced or substituted
by a different base pair)
 Example:

› GATTACA
› GATTGCA

The “A” was
replaced with a “G”
Original: the
Mutation:

fat cat ate the wee rat
the fat hat ate the wee rat
The substitution changed the meaning of
the sentence, but it is still readable
Original:
Substitution:
ATG CCG ATA GGA
ATG CCG CTA GGA
Original strand:
 Mutated strand:

Met-Pro-Iso-Gly
Met-Pro-Glu-Gly
(When a nitrogen base is inserted into
the original strand of DNA)
 Example:

› TAGCAT
› TAGCGAT

Note that an extra “G” was inserted
Original: the fat cat ate the wee rat
Insertion: the fat cat xlw ate the wee

The meaning of the sentence is still
somewhat clear
rat
Original:
Insertion:
ATG CTA CAG GGA
ATG CTA TAG CAG GGA
Original strand:
 Mutated strand:

Met-Leu-Glu-Gly
Met-Leu-STOP

Remember that these nitrogen bases
code for amino acids
› The amino acids together make proteins

One wrong letter can change all the
amino acids after it
Original:
Frame-Shift:
the fat cat ate the wee rat
the fat caa tet hew eer at
The deletion of the “t” completely
changed the meaning of the sentence
 Not only is the one word changed, every
other word after it is changed!

Original:
Frame-Shift:
ATG CTA CAG GGA TAA
ATG CTC AGG GAT AA
Original strand:
 Mutated strand:

Met-Leu-Glu-Gly-Stop
Met-Leu-Arg-Asp
 What
does a
mutation in DNA
actually change?
› Changes a protein
sequence!
Bad Science!

Everything still has to obey those pesky
laws of physics!
› No protein will give you telekinesis, flying,
shooting lasers, growing super-huge and
knowing ninjutsu, etc…
Mutations happen
 They happen with great
regularity
 Almost all mutations are
neutral
 Of the remainder,
benefit or harm
depends on
circumstances
