Mutations

• What is a mutation?

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

  continuously
• Mutations can be inherited when they occur during ...

  the formation of gameted
• define gene mutation?


  a change in the sequence of DNA bases
• Where can mutations occur and when does the risk of them occurring increase?

  During DNA replication

  they occur the most when the cells are exposed to carcinogens or radiation
• What are the 3 different ways that a mutation in the DNA base sequence can occur?

  1. substitution

  2. deletion

  3. insertion
• What are the 3 forms a substitution mutation can take?

  Silent mutations

  Missense mutations

  nonsense mutations
• What is a silent mutation?


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

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

  The mutation creates a premature stop codon (short polypeptide)
• What is a deletion mutation?


  A nucleotide is randomly deleted from the DNA sequence.
• What is a frameshift mutation?

  When an insertion or deletion mutation shifts the sequence of bases, changing the following triplet.
• Why can deletion mutations cause considerable impact?

  They can drastically change the amino acid sequence and therefore the ability of the polypeptide to function.
• What is an insertion mutation?

  A mutation that occurs when a nucleotide is randomly inserted into the DNA sequence
• What is a chromosome mutation?

  Changes in the structure or number of whole chromosomes
• describe what the changes in the whole sets of chromosomes are.

  when organisms have 3 or more sets of chromosomes known as polyploidy - occurs mostly in plants
• Describe what changes in the number of individual chromosomes are like.

  homologous pairs fail to separate during meiosis (non-disjunction) - which normally occurs during interphase.
• What can non-disjunction do to humans?

  trisomy-21 (down-syndrome)