Translation Conclusion and Mutations

Objectives

• Explain the effects of point mutations
• Explain the effects of a frameshift  mutation
• Identify causes of mutation

Translation

The chain of amino acids keeps growing until a stop codon is reached.

Options upon completion

• Assume a folded shape
• Bind with other polypeptides
• Bind with other molecules
• Travel to the Golgi apparatus

Mutations

A change in the sequence of bases in DNA or RNA is a mutation.

Mutations are essential for evolution to occur because they are the source of new alleles in a species.

Two major types of mutations

• Germline
• Somatic

Germline mutations occur in gametes. These mutations can be transmitted to offspring and every cell of the offspring will have the mutation.

Somatic mutations are confined to one cell and its daughter cells. These mutations cannot be passed to offspring.

Chromosomal alterations are mutations that change chromosome structure. A section breaks off and rejoins incorrectly or not at all.

Example

• Down syndrome

Point Mutations

• Silent (CAA -> CAG both code for glutamine)
• Missense (now codes for different AA)
• Nonsense (premature stop codon)

Point Mutations

• Silent (no effect)
• Missense (variable effect)
• Nonsense (usually serious)

A frameshift mutation is a deletion or insertion of 1+ nucleotides resulting in changes in the reading frame.

Mutation Causes

Mutagens

• Radiation (UV, x-ray)
• Chemicals (benzoyl peroxide)
• Infectious agents (HPV)

Spontaneous Mutations

• Tautomerism
• Depurination
• Deamination
• Transition
• Transversion