7.5 Flashcards
(13 cards)
Genetic Mutations
- Any changes in DNA sequence
Caused by:
Synthetic chemicals
Radiation
incorrect replication
- Mutations have driven our evolution
- Some mutations have positive effects
- Some mutations have negative effects
- Some mutations do not cause any discernible changes
Small Scale Mutations
- Point mutations
- Change in a single base pair
- Substitution – replacement of one base pair by another
*Insertion – addition of a base pair or larger coding region
- Deletion – removal of a base pair or larger coding region
- Inversion – bases switching positions
Small Scale Mutations - PT 2
- Missense Mutations
- Nonsense Mutations
- Silent Mutations
- Frameshift Mutations
Missense Mutation
- A mutation that changes a single amino acid in the coding
sequence
Nonsense Mutation
A mutation that results in a premature stop codon
Silent Mutation
A mutation that does not alter the results amino acid
sequence
Frameshift Mutation
A shift in the reading frame resulting in multiple missense/nonsense effects
- Results for an invertion or deletion
Large-Scale
Mutations
- Large-scale INSERTIONS (gene duplication or amplification)
- Leads to a large number of the same gene
- Can provide opportunities for new genes with new functions to evolve
- Large-scale DELETIONS
- Entire coding regions of DNA are removed,
negatively affecting the cell
Chromosomal
Translocation
- Mvmt of the entire gene(s)/sequences of DNA from one chromosome to another
Causes of Genetic
Mutations
- Spontaneous Mutations – caused by
errors in DNA replication
*Induced Mutations – caused by env. agents, called mutagens, that directly alters the DNA w/in a cell
- 2 of the most common mutagens are:
- Chemical Mutagens
- Radiation
Chemical Mutagens
Chemically alters the structure of DNA
Carbon Monoxide – linked to cancer
- Nitrous Acid – can modify base pairs to resemble
other base pairs, confusing the replication
machinery resulting in inaccurate copying - Benzene – bonds to nucleotides to change the
shape of DNA and negatively affect replication - Ethidium Bromide – inserts itself b/w strands of
DNA and causes replication errors
Radiation
Electromagnetic radiation can cause mutations
- UV radiation cause bonds to form in the DNA
chain that alter is shape and complicate
replication and transcription, leading to skin
cancer - X-Rays/Gamma Rays can break bonds w/in DNA molecules and cause cancer
Mutations - Positive or Negative?
- Mutations are responsible for the variety of life we see today
- A mutation that is harmful only truly affects the individual, not
the group, b/c it renders the individual less fit and will be
selected against by nature - A beneficial mutation are advantageous to the individual, as it experiences greater survival and reproductive success, and
passes that mutation on to its offspring - The majority of mutations are neutral (e.g., silent mutations)
- Occurs 90% in non-coding regions
- Mutations have a greater affect in prokaryotes b/c most of their DNA is coding
