Mutation and gene editing

• What is a gene mutation?

  A change in the sequence of base pairs in a DNA molecule
• How do mutations occur?

  Mutations occur all the time and at random
• When are mutations more likely to occur in the cell cycle?

  During the S phase of interphase when DNA is being replicated
• What can mutations in a gene lead to?


  A change in the polypeptide that the gene codes for
• What are the typical effects of most mutations?

  Most mutations are harmful or neutral
• Are mutations in normal body cells inherited?

  No, they are eliminated from the population once those cells die
• What happens to mutations within gametes?

  They are inherited by offspring, possibly causing genetic disease
• What is a substitution mutation?

  A mutation where a nucleotide base is randomly swapped for a different base
• What is the effect of a substitution mutation on the amino acid sequence?

  It only changes the amino acid for the triplet where the mutation occurs
• What is an insertion mutation?

  A mutation where a nucleotide is randomly inserted into the DNA sequence
• How does an insertion mutation affect the amino acid sequence?

  It changes the amino acid that would have been coded for by the original base triplet
• What is a frameshift mutation?

  A mutation that changes the reading frame of the DNA sequence
• What is a deletion mutation?

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


  It changes the amino acid that would have been coded for
• What are mutagenic agents?

  Environmental factors that increase the mutation rate of cells
• What types of radiation can cause mutations?

  High-energy radiation such as UV light and ionizing radiation like X-rays
• What are some chemical substances that can cause mutations?

  Benzo[a]pyrene and nitrosamines found in tobacco smoke
• How do random mutations occur during DNA replication?

  Errors in the nucleotide sequence are not detected by the proofreading process
• What is the genetic code's degeneracy?

  More than one triplet code can code for the same amino acid
• Where can mutations occur in the genome?

  Anywhere in the base sequence of a genome on all chromosomes
• What are mutation hotspots?

  Regions where mutations are more frequent
• What is a CpG site?

  A site where cytosine (C) is followed by guanine (G) and is prone to mutation
• What happens when methylation occurs at a CpG site?

  C can mutate into Thymine (T) in a substitution mutation
• What is the consequence of a nonsense mutation?

  It creates a premature stop codon, affecting the final protein structure
• What is a silent mutation?

  A mutation that does not alter the amino acid sequence of the polypeptide
• What is a missense mutation?

  A mutation that alters a single amino acid in the polypeptide chain
• What are the consequences of insertions and deletions?

  They can cause frameshift mutations, impacting the entire amino acid sequence
• How does a frameshift mutation affect protein synthesis?

  It causes a complete change to the entire amino acid sequence after the mutation site
• What is the difference between germ cells and somatic cells?

  Germ cells use meiosis to produce gametes, while somatic cells use mitosis
• What happens if a mutation occurs in a germ cell?

  It can be passed on to the offspring and next generation
• What are oncogenes?

  Mutated genes that cause cancer
• How do mutations contribute to genetic variation?

  They result in small differences in DNA base sequences between individuals
• What is an advantageous allele?


  An allele that increases the chance of survival and reproduction
• What is a disadvantageous mutation?

  A mutation that is less likely to be passed on to the next generation
• What are differences in characteristics among individuals known as?

  Variation
• What are some examples of variation?

  • Coat colour in mammals
  • Body length in fish
  • Flower colour in flowering plants
• What causes variation among organisms in a population?

  Small differences in DNA base sequences
• What are the sources of differences in DNA base sequences?

  1. Mutation
  2. Meiosis
  3. Random fertilization during sexual reproduction
• What is the original source of genetic variation?

  Mutation
• How do mutations influence evolution?

  They generate new alleles that can affect a species' evolution