9.1 - Mutations

Question 1

What is the definition of a mutation

Answer 1

Any change to the quantity of the base sequence of DNA of an organism

Question 2

What is the definition of a gene mutation

Answer 2

Any change to one or more nucleotide bases, or a change in the sequence of the bases in DNA

Question 3

When do gene mutations arise

Answer 3

DNA replication

Question 4

What is a substitution of bases

Answer 4

• Type of gene mutation
  —> a nucleotide in a DNA molecule is replaced by another nucleotide that has a different base

Question 5

Describe the polypeptide produced as a result of substitution

Answer 5

• polypeptide produced varies in a single amino acid
• significance of this depends on the role of the amino acid:
  —> if important in forming the bonds that create the tertiary structure = the replaced amino acid may not form the same bonds = affects shape of protein and its functionality (e.g. enzyme)

Question 6

Why might substitution be hard to detect

Answer 6

• genetic code is often called the degenerate code (amino acids have more than 1 codon)
• this means that there’s a chance it won’t affect the polypeptide produced
• called a silent mutation

Question 7

What is deletion of bases

Answer 7

• a type of genetic mutation
  —> arises when a nucleotide is lost from the normal DNA sequence

Question 8

What is the consequence of a deletion of bases

Answer 8

• amino acid sequence is entirely different due to a frame shift = polypeptide is highly unlikely to work properly

Question 9

What is a chromosome mutation

Answer 9

Change in the structure or number of whole chromosomes

Question 10

What are the 2 different forms of chromosome mutations

Answer 10

• Changes in whole sets of chromosomes
• changes in the number of individual chromosomes

Question 11

Describe changes in whole sets of chromosomes (a form of chromosome mutation)

Answer 11

• occur when organisms have 3 or more sets of chromosomes rather than the usual 2
• this condition is called polyploidy
• occurs mostly in plants

Question 12

Describe changes in the number of individual chromosomes (form of chromosome mutation)

Answer 12

• sometimes individual homologous pairs of chromosomes fail to separate during meiosis (known as non-disjunction) and usually results in a gamete having 1 more or 1 fewer chromosome
• on fertilisation with a gamete that doesn’t have the normal complement of chromosomes, the resultant offspring have, more or fewer chromosomes than normal in all their body cells
• an example of this would be Down’s syndrome