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Worksheet: Mutations Practice Questions, Exercises of Genetics

A mutation is a change that occurs in our DNA sequence, either due to mistakes when the DNA is copied or as the result of environmental factors such as UV light and cigarette smoke.

Typology: Exercises

2020/2021

Uploaded on 04/20/2021

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Ms. DR’s Biology 621
Name: _____________________________________________________________Block: ____________ Date: ________________
Worksheet: Mutations Practice
There are three ways that DNA can be altered when a mutation (change in DNA
sequence) occurs.
1. Substitution one base-pairs is replaced by another:
Example: G to C or A to G
C G T C
2. Insertion one or more base pairs is added to a sequence:
Example: CGATGG –– CGAATGG
GCTACC GCTTACC
3. Deletion one or more base pairs is lost from a sequence:
Example: CGATGG –– CATGG
GCTACC GTACC
There are five possible results of a mutation.
1. Silent mutation: When a base pair is substituted but the change still codes for
the same amino acid in the sequence:
Example: TCT and TCC both code for the amino acid Serine
2. Substitution: When a base pair is substituted and the new codon codes for a
different amino acid:
Example: TCT codes for Serine and CCT codes for Proline
3. Premature Stop: When a substitution results in the formation of a STOP codon
before all of the codons have been read and translated by the ribosome.
Example: GTGGTCCGAAACACC –– GTGGTCTGAAACACC
Val-Val-Pro-Asn-Thr Val-Val-STOP
4. Codon Deletion or Insertion: A whole new amino acid is added, or one is
missing from the mutant proton:
Example: GTGGTCCGAAACACC –– GTGGTCTGCCGAAACACC
Val-Val-Pro-Asn-Thr Val-Val-Cys-Pro-Asn-Thr
5. Frame Shift: When a deletion or insertion results in a different base pait being
the beginning of the next codon, changing the whole sequence of amino acids
Example: GTGGTCCGAAACACCT –– GTGGTCGAAACACCT
Val-Val-Pro-Asn-Thr Val-Val-Glu-Thr-Pro
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Name: _____________________________________________________________Block: ____________ Date: ________________

Worksheet: Mutations Practice

There are three ways that DNA can be altered when a mutation (change in DNA sequence) occurs.

  1. Substitution – one base-pairs is replaced by another: Example: G to C or A to G C G T C
  2. Insertion – one or more base pairs is added to a sequence: Example: CGATGG –– CGA A TGG GCTACC GCT T ACC
  3. Deletion – one or more base pairs is lost from a sequence: Example: C G ATGG –– CATGG G C TACC GTACC There are five possible results of a mutation.
  4. Silent mutation: When a base pair is substituted but the change still codes for the same amino acid in the sequence: Example: TC T and TC C both code for the amino acid Serine
  5. Substitution: When a base pair is substituted and the new codon codes for a different amino acid: Example: T CT codes for Serine and C CT codes for Proline
  6. Premature Stop: When a substitution results in the formation of a STOP codon before all of the codons have been read and translated by the ribosome. Example: GTGGTC C GAAACACC –– GTGGTC T GAAACACC Val-Val-Pro-Asn-Thr Val-Val-STOP
  7. Codon Deletion or Insertion: A whole new amino acid is added, or one is missing from the mutant proton: Example: GTGGTCCGAAACACC –– GTGGTC TGC CGAAACACC Val-Val-Pro-Asn-Thr Val-Val-Cys-Pro-Asn-Thr
  8. Frame Shift: When a deletion or insertion results in a different base pait being the beginning of the next codon, changing the whole sequence of amino acids Example: GTGGTC C GAAACACCT –– GTGGTCGAAACACCT Val-Val-Pro-Asn-Thr Val-Val-Glu-Thr-Pro

Name: _____________________________________________________________Block: ____________ Date: ________________

  1. Below is the base sequence for the normal protein for normal hemoglobin and the base sequence for the sickle cell hemoglobin. Normal: GGG CTT CTT TTT Sickle: GGG CAT CTT TTT a. Transcribe and translate the normal and sickle cell DNA. b. Identify this as a point or frameshift mutation. Explain. c. If the base sequence read GGG CTT CTT AAA instead, would this result in sickle cell hemoglobin? Explain. normal: mRNA: CCC GAA GAA AAA normal Amino Acid: PRO GLU GLU LYS sickle: mRNA: CCC GUA GAA AAA sickle amino acid: PRO VA L GLU LYS It is a point mutation of the misense kind: a single base substitution in the normal mRNA caused a different amino acid to be added. mRNA: CCC GAA GAA UUU Amino Acid: PRO GLU GLU PHE Yes. The "normal" amino acid "LYS" got replaced by "PHE"

Name: _____________________________________________________________Block: ____________ Date: ________________ Original DNA Sequence : T A C A C C T T G G C G A C G A C T mRNA Sequence: Amino Acid Sequence: Mutated DNA Sequence #1: T A C A T C T T G G C G A C G A C T What’s the mRNA sequence? (Circle the change) What will be the amino acid sequence? Will there likely be effects? What kind of mutation is this? Mutated DNA Sequence #2: T A C G A C C T T G G C G A C G A C T What’s the mRNA sequence? (Circle the change) What will be the amino acid sequence? Will there likely be effects? What kind of mutation is this? Mutated DNA Sequence #3: T A C A C C T T A G C G A C G A C T What’s the mRNA sequence? (Circle the change) What will be the amino acid sequence? Will there likely be effects? What kind of mutation is this? Mutated DNA Sequence #4: T A C A C C T T G G C G A C T A C T What’s the mRNA sequence? (Circle the change) What will be the amino acid sequence? Will there likely be effects? What kind of mutation is this? Mutated DNA Sequence #5: T A C A C C T T G G G A C G A C T What will be the corresponding mRNA sequence? What will be the amino acid sequence? Will there likely be effects? What kind of mutation is this?

Name: _____________________________________________________________Block: ____________ Date: ________________

  1. Which type of mutation is responsible for new variations (alleles) of a trait?
  2. Which type of mutation results in abnormal amino acid sequence?
  3. Which type of mutation stops the translation of the mRNA?