2.4.1 Types of Mutations

• Frameshift mutations can drastically change the resulting codons and amino acids in a DNA sequence.
• What are the two main types of chromosome mutations?

  Structural, numerical
• A structural mutation called a deletion involves the loss of a chromosome segment.
• Aneuploidy involves having extra or missing chromosomes, such as in Down Syndrome.
• What chromosome is affected in Down Syndrome?

  Chromosome 21
• Spontaneous errors during DNA replication are caused by mistakes made by DNA polymerase.
• What are genetic mutations?

  Changes in the DNA sequence
• Point mutations involve changes in a single nucleotide base pair.
• Genetic mutations can occur spontaneously or be induced by mutagens
• Match the type of mutation with its description:

  Point Mutations ↔️ Change in a single nucleotide

  Frameshift Mutations ↔️ Insertion or deletion of nucleotides

  Chromosomal Mutations ↔️ Changes in chromosome structure
• Genetic mutations always lead to harmful effects on organisms.

  False
• Genetic mutations can affect gene expression and an organism's phenotype
• Arrange the types of point mutations in order of their effect on the amino acid sequence:

  1️⃣ Synonymous

  2️⃣ Missense

  3️⃣ Nonsense
• What is an example of a synonymous mutation?

  $GUU$ to $GUC$
• Point mutations can result in nonsense mutations.
• Point mutations involve a change in a single nucleotide
• Match the type of mutation with its effect:

  Frameshift Mutation ↔️ Shifts reading frame

  Point Mutation ↔️ May change amino acid sequence

  Chromosomal Mutation ↔️ Changes chromosome structure
• Point mutations can have different effects depending on the nature of the substitution.
• Order the types of point mutations based on their effects:

  1️⃣ Synonymous (no change in amino acid)

  2️⃣ Missense (change to a different amino acid)

  3️⃣ Nonsense (change to a stop codon)
• A change from $GUU$ to $GUC$ is a synonymous mutation because both code for valine
• Frameshift mutations typically result in non-functional proteins.
• What is the effect of a frameshift mutation on the amino acid sequence?

  Shifts reading frame
• If an $A$ is inserted into the sequence $ATC - GAT - CGA$, the new sequence becomes ATC - A - GAT - CGA
• What are the two categories of chromosome mutations?

  Structural and numerical
• Aneuploidy involves having extra or missing chromosomes.
• Triploidy, where an organism has three sets of chromosomes, is an example of polyploidy
• Numerical changes in chromosomes include aneuploidy and polyploidy
• A deletion in a chromosome mutation results in the loss of a chromosome segment
• An inversion in a chromosome mutation refers to the reversal of a chromosome segment
• What is an example of aneuploidy in humans?

  Trisomy 21
• Structural changes in chromosomes include deletions, duplications, inversions, and translocations
• What causes Down syndrome?

  Aneuploidy
• Genetic mutations can only occur spontaneously

  False
• Match the type of genetic mutation with its description:

  Point Mutations ↔️ Change in a single nucleotide base pair

  Frameshift Mutations ↔️ Insertion or deletion of nucleotides that shift the reading frame

  Chromosomal Mutations ↔️ Changes in chromosome structure or number
• Synonymous mutations result in no change in the encoded amino acid.
• What type of point mutation changes a codon to code for a different amino acid?

  Missense
• Frameshift mutations occur when nucleotides are inserted or deleted in multiples of three

  False
• Spontaneous errors during DNA replication are made by DNA polymerase
• What is an example of a chemical mutagen that mimics DNA bases?

  Base analog
• UV radiation can cause thymine dimers