Biology, Eighth Edition (Raven)

Chapter 15: Genes and How They Work

Addition and Deletion Mutations

At what stages in the cell cycle can additions or deletions of DNA occur? Cells have elaborate molecular machinery to find and correct DNA errors. Why do errors in DNA replication occur? Damage to DNA from chemicals, radiation, or other factors can occur at any time. If these changes are not detected and repaired they will passed along during DNA replication. Breaks in the DNA followed by repair can result in lost DNA. Errors can also occur during DNA replication itself. These are usually substitutions rather than additions or deletions. The most common point in the cell cycle for addition and deletion mutations is during meiosis. Mistakes in pairing during synapsis can result in unequal exchange of DNA between homologous chromosomes.

View the animation below, then complete the quiz to test your knowledge of the concept.


The nucleic acid sequence in mRNA is determined by
A)the order of amino acids in the protein
B)nucleotide sequence in DNA
C)nucleotide sequence in t-RNA
D)all of the above

If a frameshift mutation causes a stop codon to be inserted into the DNA sequence
A)the resulting protein will not be affected
B)the phenotype will change but not the genotype
C)the resulting protein will be too short and non-functional
D)the resulting protein will be too long and non-functional

A nucleotide deletion in DNA replication
A)causes one amino acid of the protein to be incorrect
B)causes all of the amino acids of the protein to be incorrect
C)causes the amino acids inserted after the deletion to be incorrect
D)causes the amino acids inserted before the deletion to be incorrect
E)has no effect on the resulting protein

The addition of a single nucleotide to the DNA sequence causes a frameshift mutation.

In a frameshift mutation all of the amino acids before the shift are changed.
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