- Insertion: The addition of one or more nucleotides into a DNA sequence, which can alter the reading frame if not in multiples of three.
- Deletion: The removal of one or more nucleotides from a DNA sequence, which can also cause a frameshift if not in multiples of three.
- Substitution: The replacement of one nucleotide with a different nucleotide; may result in silent, missense, or nonsense mutations depending on the effect on the amino acid sequence.
- Mutation #1 (Gene): Type of mutation: Substitution. The original DNA codon "GGA" is changed to "GGC", both coding for glycine — this is a silent mutation.
- Mutation #2 (Gene): Type of mutation: Substitution. The original DNA codon "GGA" is changed to "GAA", which codes for glutamic acid instead of glycine — this is a missense mutation.
- Mutation #3 (Gene): Type of mutation: Insertion. An extra "C" is inserted after the first "T", shifting the reading frame and altering all subsequent codons.
- Mutation #4 (Gene): Type of mutation: Deletion. The "C" at position 5 is deleted, causing a frameshift that changes the downstream amino acid sequence.
- Mutation #1 (Chromosome): Type of mutation: Inversion. Segments D-E-F are inverted to F-E-D within the same chromosome.
- Mutation #2 (Chromosome): Type of mutation: Duplication. Segment D-E-F is duplicated, resulting in two copies of that segment.
- Mutation #3 (Chromosome): Type of mutation: Insertion (or duplication). Segment E is inserted again, creating a tandem repeat.
- Mutation #4 (Chromosome): Type of mutation: Deletion. Segments d-e-f-g are deleted from the chromosome.
- Frameshift: A mutation that alters the reading frame of codons by inserting or deleting nucleotides not in multiples of three, leading to a completely different amino acid sequence downstream. Of the three gene mutations, insertion and deletion can cause a frameshift; substitution does not.
- Most dramatic effect on protein structure: Insertion and deletion (frameshift mutations), because they change every subsequent amino acid in the polypeptide chain, often leading to nonfunctional or truncated proteins.
- Most dramatic effect on an organism (chromosome level): Translocation or large deletions, because they can disrupt multiple genes, regulatory regions, or cause loss of essential genetic material, potentially leading to developmental disorders or cancer.
- Most damaged cells by mutations: Germ-line cells (sperm and egg cells), because mutations here can be passed to offspring and affect every cell in the next generation; somatic cells can also be severely affected if mutations occur in critical genes like tumor suppressors.
- Mutation during DNA Replication: Errors by DNA polymerase can lead to base substitutions, insertions, or deletions if not corrected by proofreading or mismatch repair.
- Mutation during Anaphase: Non-disjunction can cause chromosomal mutations like aneuploidy, where daughter cells receive abnormal numbers of chromosomes.
- Mutation during Crossing Over in Meiosis: Unequal crossing over can lead to duplications or deletions of chromosomal segments; recombination between non-homologous chromosomes can cause translocations.
Parent Tip: Review the logic above to help your child master the concept of mutations practice worksheet.
