Download Acids and Bases Lab

Name:
30 Points
Period:
Gene Mutations
Background: Large-scale mutations affect the entire chromosome or number of
chromosomes. Point mutations are small-scale, but can seriously affect the gene being
copied. There is an error in around every 100,000 base pairs copied, but there are proofreading abilities within the enzymes that copy the DNA or RNA. However, nothing is
foolproof. This handout describes the common mutations, and how they affect the entire
sequence.
1) Prediction: What will happen if just one base pair is added or removed to a DNA
sequence being replicated?
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FRAMESHIFT MUTATIONS:
DNA sentence
The man hit his eye and saw the red dot
Insertion example
t
The man hit hi sey ean dsa wth ere ddo t
The insertion shifts the readDin gfram et oth eright. The deletion shifts the rea(d)ingf
ramet ot hel eft. Complete the following lines for frameshift mutations.
WRITE EACH CODON PER LINE
DNA sentence
2) Insertion
3) Deletion
The man hit
his
eye
and
saw
the
red
dot
The man ____ ____ ____ ____ ____ ____ ____ ____
Insert a R after the h
 the three letter words should shift down
The man hit
Delete the I here
____ ____ ____ ____ ____ ____ ____
 the three letter words should shift down
Now use real DNA code and translate it into the correct amino acids. Decide where in
the original DNA code to cause a mutation on the rest of the questions. Please use the
codon table on the last page to find the corresponding amino acids.
WRITE EACH CODON PER LINE AND CIRCLE THE MUTATED DNA BASE WHERE
THE MUTATION TAKES PLACE.
Original DNA TAC
GGA
4) Insertion
TCT
CAG
GAG
CCT
ATA
ATC
____
____ ____
Insert a C after the G

____
____
____
____
____
____
____
CGA
5) Mutated mRNA
____
____
____
____
____
____
____
____
____
6) Mutated Amino
____
____
____
____
____
____
____
____
____
Original Amino acids MET PRO
ALA ARG VAL LEU
GLY TRY
STOP
7) How did the mutation affect the amino acid sequence?
WRITE EACH CODON PER LINE AND CIRCLE THE MUTATED DNA BASE WHERE
THE MUTATION TAKES PLACE.
Original DNA
TAC
GGA
CGA
TCT
CAG
GAG
CCT
ATA
ATC
8) Deletion
____
____
____

____
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____
____
____
____
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____
_N/A_
____ ____
____
____
____
____
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____
_N/A_
GLY TRY
STOP
Delete the G
9) Mutated mRNA
10) Mutated Amino
____
Original Amino acids MET PRO
ALA ARG VAL LEU
11) How did the mutation affect the amino acid sequence?
Base Substitution Mutations (Point mutations):
A different type of gene mutation is called base substitution or point mutation. It is the
simplest type of mutation where a nucleotide pair is replaced with a different nucleotide
pair.
Base substitution
GACGGC
This may be a silent mutation, is which the amino acid is not affected.
For example, the base substitution G A C G A G doesn’t change much since the
mRNA would be C U G or C U C, both of which code for Leucine.
WRITE EACH CODON PER LINE AND CIRCLE THE MUTATED DNA BASE WHERE
THE MUTATION TAKES PLACE.
Original DNA
TAC
CAT
TCT
TGT
AAA
AGG
GCG
ATT
12) Silent DNA
____
____
____
____ ____
Change the last G to a C

____
____
____
____
13) Mutated mRNA ____
____
____
____
____
____
____
____
____
____ ____
____
____
____
____
____
____
____
Original Amino acids MET VAL ARG ALA THR
PHE
SER
ARG STOP
14) Mutated Amino
CGG
15) How did the mutation affect the amino acid sequence?
If there is a change that affects which amino acid is made, then the entire gene being
made may be mutated.
The two types of this are misssense and nonsense mutations.
Missense mutation changes one or more amino acids. This may completely change the
function of a gene. For example, G G A would code as C C U on mRNA, which is
Proline. If a base was changed to G A A, then it would code as C U U, which is Leucine.
WRITE EACH CODON PER LINE AND CIRCLE THE MUTATED DNA BASE WHERE
THE MUTATION TAKES PLACE.
Original DNA
TAC
GTC
GCT
CAA
CGG
GAC
CTG
ACC
ACT
16) Missense DNA
____
____
____
____
____

____
____
____
____
Change the middle G to a C
17) Mutated mRNA ____
____
____
____
____
____
____
____
____
____ ____
____
____
____
____
____
____
____
Original Amino acids MET GLN ARG VAL ALA LEU
ASP
TRP
STOP
18) Mutated Amino
19) How did the mutation affect the amino acid sequence?
Nonsense mutation changes the amino acid to a premature stop codon, stopping or
altering the formation of the protein.
WRITE EACH CODON PER LINE AND CIRCLE THE MUTATED DNA BASE WHERE
THE MUTATION TAKES PLACE.
Original DNA
TAC
GGT
AAT
CAA
ATA
GAA
CCT
GAG
ACT
____
____
____

____
____
____
____
____
____
____
____
____
____
____
____
____
____
____ ____
____
____
____
____
____
____
____
Original Amino acids MET PRO
LEU
VAL TYR
LEU
GLY LEU
20) Nonsense DNA
Change the second A to a C
21) Mutated mRNA ____
22) Mutated Amino
STOP
23) How did the mutation affect the amino acid sequence?
Questions:
24) An error occurs in about how many base pairs being copied?
25) If there are 3 billion base pairs, why don’t all these mistakes in the DNA replication
process cause a mutation every time there is a mistake?
26-27) Explain how mutations may be harmful and/or helpful to organisms
(don’t list super-powers here)
27-30) List the 4 of the different types of mutations discussed in this activity. Deletion
and insertion count as one type of mutation.
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