DNA Mutations Flashcards
What is the difference between a germline and somatic mutation?
Germ line
- DNA of sperm/eggs
- Transmitted to offspring
- Found in every cell in the body
Somatic mutations
- Acquired during lifespan of cell
- Not transmitted to offspring
What is a transition mutation?
Purine to purine or pyrimidine to pyrimidine
What is a transversion mutation?
Purine to pyrimidine or pyrimidine to purine
What is more common a transition or transversion point mutation?
Transition (purine to purine or pyrimidine to pyrimidine)
Where is the most common position for a silent mutation to occur?
3rd position of codon
- NT substitution codes for the same amino acid
What does a nonsense mutation result in?
Early stop codon
- Nucleotide triplet
- Signals termination of translation of proteins
What are the stop codons?
UGA, UAA, UAG
What kind of point mutation is a NT substitution which results in the coding of a different amino acid which alters the protein formed?
Missense mutation
What substitution of bases occurs in sickle cell anemia?
Adenine changed for thymine
Where is the missense mutation in sickle cell?
6th codon of Beta chain gene
- chromosome 11p15
What is glutamate substituted for in sickle cell?
Valine
What kind of mutation is CF (delta F508)?
How many bases are affected?
Deletion
- 3
CF (delta F508 type) causes the loss of what protein?
What does this result in?
Loss of phenylalanine
- Abnormal protein folding
What does a frameshift mutation do?
Alters the reading frame
- Many amino acids may change
How can an insertion/deletion mutation not cause a frameshift mutation?
If it is not a multiple of 3
Tay Sachs disease what type of disease?
Frameshift
What gene is altered in Tay Sachs disease?
Hexosaminidase A
Duchenne muscular dystrophy is what type of mutation and affects what gene?
Frameshift deletions which causes an absence of functional Dystrophin
Why is becker muscular dystrophy far milder form of muscular dystrophy?
It is not frameshift
Where does slipped-strand Mispairing (or DNA slipping) occur?
Areas of repeated NT sequences
What will DNA slippage cause in the template and then replicated strand?
- Deletion in template strand (DNA not replicated)
- Insertion in replicated strand (replicated strand longer)
What are examples of diseases with trinucleotide repeats?
- Fragile X syndrome
- Huntington’s
- Friedreich’s ataxia
- Myotonic dystrophy
What kind of diseases are thought to be due to DNA slippage?
Trinucleotide repeat disorders
What are microsatellites?
- Short segments of DNA with repeated sequences (i.e. CACACACA)
What makes microstellites unstable?
Possibility for DNA slippage
- If mismatch repair enzymes fail -> instability
- There will be a variation (instability) in the size of segments among cells
What cancer is involved with microsattelite instability?
Colon cancer
