DNA Mutations

Question 1

What is the difference between a germline and somatic mutation?

Answer 1

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

Question 2

What is a transition mutation?

Answer 2

Purine to purine or pyrimidine to pyrimidine

Question 3

What is a transversion mutation?

Answer 3

Purine to pyrimidine or pyrimidine to purine

Question 4

What is more common a transition or transversion point mutation?

Answer 4

Transition (purine to purine or pyrimidine to pyrimidine)

Question 5

Where is the most common position for a silent mutation to occur?

Answer 5

3rd position of codon

- NT substitution codes for the same amino acid

Question 6

What does a nonsense mutation result in?

Answer 6

Early stop codon

• Nucleotide triplet
• Signals termination of translation of proteins

Question 7

What are the stop codons?

Answer 7

UGA, UAA, UAG

Question 8

What kind of point mutation is a NT substitution which results in the coding of a different amino acid which alters the protein formed?

Answer 8

Missense mutation

Question 9

What substitution of bases occurs in sickle cell anemia?

Answer 9

Adenine changed for thymine

Question 10

Where is the missense mutation in sickle cell?

Answer 10

6th codon of Beta chain gene

- chromosome 11p15

Question 11

What is glutamate substituted for in sickle cell?

Answer 11

Valine

Question 12

What kind of mutation is CF (delta F508)?

How many bases are affected?

Answer 12

Deletion

- 3

Question 13

CF (delta F508 type) causes the loss of what protein?

What does this result in?

Answer 13

Loss of phenylalanine

- Abnormal protein folding

Question 14

What does a frameshift mutation do?

Answer 14

Alters the reading frame

- Many amino acids may change

Question 15

How can an insertion/deletion mutation not cause a frameshift mutation?

Answer 15

If it is not a multiple of 3

Question 16

Tay Sachs disease what type of disease?

Answer 16

Frameshift

Question 17

What gene is altered in Tay Sachs disease?

Answer 17

Hexosaminidase A

Question 18

Duchenne muscular dystrophy is what type of mutation and affects what gene?

Answer 18

Frameshift deletions which causes an absence of functional Dystrophin

Question 19

Why is becker muscular dystrophy far milder form of muscular dystrophy?

Answer 19

It is not frameshift

Question 20

Where does slipped-strand Mispairing (or DNA slipping) occur?

Answer 20

Areas of repeated NT sequences

Question 21

What will DNA slippage cause in the template and then replicated strand?

Answer 21

• Deletion in template strand (DNA not replicated)

- Insertion in replicated strand (replicated strand longer)

Question 22

What are examples of diseases with trinucleotide repeats?

Answer 22

• Fragile X syndrome
• Huntington’s
• Friedreich’s ataxia
• Myotonic dystrophy

Question 23

What kind of diseases are thought to be due to DNA slippage?

Answer 23

Trinucleotide repeat disorders

Question 24

What are microsatellites?

Answer 24

• Short segments of DNA with repeated sequences (i.e. CACACACA)

Question 25

What makes microstellites unstable?

Answer 25

Possibility for DNA slippage

• If mismatch repair enzymes fail -> instability
• There will be a variation (instability) in the size of segments among cells

Question 26

What cancer is involved with microsattelite instability?

Answer 26

Colon cancer