Genetic Mutations

Question 1

What are the different types of gene mutations?

Answer 1

• addition
• deletion
• substitution
• inversion
• duplication
• translocation

Question 2

What are addition mutations?

Answer 2

• when a base is randomly added to a DNA sequence, resulting in a frame shift to the right
• harmful bc alters all successive codons, which can potentially code for diff AAs, resulting in a diff sequence of AAs + so a non-functioning protein

Question 3

What are deletion mutations?

Answer 3

• when a base is randomly deleted from a DNA sequence, resulting in a frame shift to the left
• harmful bc alters all previous codons, which can potentially code for diff AAs, resulting in a diff sequence of AAs + so a non-functioning protein

Question 4

What are substitution mutations?

Answer 4

• when a base in DNA sequence is randomly swapped for a diff. base, resulting in only 1 codon changing
• NO° of bases remain the same, so there’s no frame shift
• bc genetic code is degenerate, it can still code for same AA + so have no effect

Question 5

What are inversion mutations?

Answer 5

• when a section of bases detach from a DNA sequence + are inverted when re-joined, so section of code is back to front
• results in diff AAs being coded for in this section, resulting in a diff sequence of AAs + so a non-functioning protein

Question 6

What are duplication mutations?

Answer 6

• when a section of DNA bases are duplicated within the DNA sequence, resulting in a frame shift to the right

Question 7

What are translocation mutations?

Answer 7

• when a section of bases in a DNA sequence on 1 chromosome, detaches + attaches onto a diff chromosome
• can cause sig. impacts on gene expression + so resulting phenotype

Question 8

When do gene mutations usually occur?

Answer 8

• during DNA replication, which is during interphase in cell cycle

Question 9

What do gene mutations result in?

Answer 9

• a diff AA sequence in polypeptide chain, so when protein is modified into tertiary structure, H + ionic bonds form in diff places + fold differently, = a diff 3D shape, + so a non functioning protein
• however, some mutations have no effect bc codons are degenerate, + so can result in same AA being produced

Question 10

What causes gene mutations?

Answer 10

• mutations occur spontaneously, but frequency can be inc by mutagenic agents

Question 11

What are the types of mutagenic agents?

Answer 11

• high energy + ionising radiation: α + β particles, x-rays + gamma rays (UV light isn’t ionising, but is high enough to damage + disrupt DNA structure)
• carcinogens (chemicals that alter DNA structure + interfere w transcription): chemicals in tobacco smoke, mustard gas + peroxides