Gene Mutations

• What is a gene mutation?

  A change in the DNA base sequence
• What may result from a gene mutation?

  An altered polypeptide
• How often do mutations occur?

  Continuously
• What can increase the probability of a mutation?

  The presence of mutagens
• How can ionising radiation affect DNA?

  It can break DNA strands
• What do deaminating chemicals do to DNA?

  They alter the chemical structure of bases
• What is the effect of adding methyl or ethyl groups to bases?

  It leads to incorrect base pairing
• How can viruses affect DNA?

  They can insert viral DNA into host DNA
• Why do most mutations have no effect on organisms?

  They do not alter the polypeptide
• What is the genetic code's degeneracy?

  Several triplets code for the same amino acid
• What can happen when a mutation occurs in a gene?

  It can change the polypeptide coded by the gene
• What are the three main ways a mutation can occur?

  Insertion, deletion, substitution
• What is an insertion mutation?

  A nucleotide is randomly inserted into DNA
• What effect does an insertion mutation have?

  It changes the amino acid coded by the triplet

  
• What is a frameshift mutation?

  A mutation that changes the triplets further in the sequence
• What is a deletion mutation?

  A nucleotide is randomly deleted from DNA
• How does a deletion mutation affect the amino acid sequence?

  It changes the amino acid coded by the triplet

  
• What is a substitution mutation?

  A base is swapped for a different base
• How does a substitution mutation affect the amino acid sequence?

  It only changes the specific triplet affected

  
• What are the three forms of substitution mutations?

  Silent, missense, nonsense
• What is a silent mutation?

  It does not alter the amino acid sequence
• What is a missense mutation?

  It alters a single amino acid in the polypeptide
• What is a nonsense mutation?

  It creates a premature stop codon
• How can gene mutations be categorized?

  Beneficial, harmful, neutral
• What is a beneficial mutation?

  A mutation that results in advantageous traits
• How can a beneficial mutation affect an enzyme?

  It may change the active site's shape
• What is a harmful mutation?

  A mutation that causes detrimental effects
• What is a neutral mutation?

  A mutation with no selective advantage or disadvantage
• What is a silent mutation?

  A change that results in the same amino acid
• What is the significance of the first two nucleotides in a codon?

  They determine the amino acid coded