Genetic Mutations

Q: What are genetic mutations?

A: Genetic mutations are changes in the DNA sequence.

Q: What can cause genetic mutations?

A: Synthetic chemicals, radiation, incorrect replication, and non-regulated cell division.

Q: What are the two types of mutations?

A: Spontaneous mutations and induced mutations.

Q: What is a spontaneous mutation?

A: A mutation caused by an error in DNA replication.

Q: What is an induced mutation?

A: A mutation caused by environmental agents (mutagens).

E.g. UV rays and tobacco smoke.

Cancer

• Cancer cells lack the ability to regulate cell division.

• When unregulated cell division occurs, there is a higher probability of  mutations arising

• This can lead to a tumor

• • Benign: non-life threatening

  • Malignant: becomes cancerous

Q: What is a point mutation?

A: A change within a single nucleotide within a gene.

Q: What types of changes are included in point mutations?

A: Substitution, insertion, deletion, and inversion.

Q: What is substitution?

A: The replacement of one base pair in a DNA sequence by another base pair.

Q: What is insertion?

A: The addition of a base pair or larger coding region to a DNA sequence.

Q: What is deletion?

A: The removal of a base pair or larger coding region from a DNA sequence.

Q: What is inversion?

A: Two adjacent bases trading places or the reversal sequence of DNA.

Q: What do large-scale mutations involve?

• Large scale mutations involves multiple

nucleotides, entire genes or whole regions of

chromosomes

What are examples of large scale mutations? 

• Duplication

• Genes are copied to multiple regions of chromosomes

• Large-scale deletions/insertions

• Entire coding regions of DNA are deleted or inserted

• Translocations

• Movement of entire genes/sequences of DNA from one chromosome to another

Q: What effects can mutations have on DNA functionality?

Mutations can have positive, negative or no effects on the functionality of DNA

Q: What are the four categories of mutations?

A: Missense mutations, nonsense mutations, silent mutations, and frameshift mutations.

Missense Mutation

• This occurs when a change of a single base pair results in the code for a different amino acid.

• The protein will have a different sequence and structure, and it may be functional or non-functional.

• It could be beneficial, as it can create a new desirable gene.

Nonsense Mutation

• This occurs when the change of a single base pair or group of base pairs results in a premature stop code in a gene.

• The polypeptide is cut short.

• Most likely will not function.

Silent Mutation

• This occurs when the change in one or more base pairs does not affect the functioning of the gene
• New DNA strand codes for the same protein as the non-mutated strand

Frame Shift Mutation

• This occurs when one or more nucleotides are inserted or deleted from a DNA sequence
• Causes the reading frame of codons to shift in one direction or the other – different protein can be made
• However, any deletion/insertion of codons (multiples of three) will not cause frameshifts