Mutations

Question 1

What is a germline mutations?

Answer 1

A mutation that occurs during meiosis.

Question 2

Where are germline mutations inherited?

Answer 2

In offspring.

Question 3

What is a somatic mutation?

Answer 3

A mutation that occurs during mitosis.

Question 4

Where is a somatic mutation inherited?

Answer 4

In daughter cells.

Question 5

What is a point mutation?

Answer 5

Alteration to a single base.

Question 6

What is a transversion?

Answer 6

Point mutation-swapping of purines and pyrimidines.

Question 7

What is a transition?

Answer 7

Point mutation-purine to purine.

Question 8

What are indels?

Answer 8

Small insertions or deletions in the sequence.

Question 9

Can point mutations occur in non-coding regions?

Answer 9

Yes. May affect regulatory elements, untranslated regions, or splice sites.

Question 10

Silent mutation

Answer 10

A change in the sequence of DNA that does not change amino acid

Question 11

Missense mutation

Answer 11

A single nucleotide change results in a codon that codes for a different amino acid.

Question 12

Nonsense mutation

Answer 12

A single nucleotide change results in a stop codon.

Question 13

Frameshift mutation

Answer 13

An indel that shifts the way the sequence is read.

Question 14

Breakpoint???

Answer 14

occurs in gene

Question 15

Position effects

Answer 15

• euchromatic to heterochromatic region

- moved near regulatory elements of other genes

Question 16

What are 3 common types of spontaneous mutations?

Answer 16

1. Depurination
2. Tautomeric shift
3. Trinucleotide repeats

Question 17

What is a depurination?

Answer 17

• Spontaneous mutation
• Loss of an adenine or guanine.
• Repaired with random base.

Question 18

What is a tautomeric shift?

Answer 18

• Spontaneous mutation
• Unstable and stable forms of ATCG
• With unstable forms, get A/C and T/G pairs

Question 19

What is a mutagen?

Answer 19

An agent that alters the structure of DNA in some way.

Question 20

What are intercalating agents?

Answer 20

• Mutagen
• Interferes with DNA replication
• Insert between bases, distort helix

Question 21

What are base analogs?

Answer 21

• Mutagen

- Incorporate into daughter strands during replication (chemotherapeutics)

Question 22

Ionizing radiation

Answer 22

• mutagen
• penetrate deep into body
• short wavelength, high energy
• deletions, single strand breaks, cross-linking, etc

Question 23

Non-ionizing radiation

Answer 23

• mutagen
• penetrate through outer body surface
• formation of thymine dimers

Question 24

General mechanism of DNA repair

Answer 24

1. Detection of alteration/damage
2. Abnormal DNA removed
3. Normal DNA synthesized

Question 25

Direct repair

Answer 25

An enzyme recognizes an incorrect alteration in DNA structure and directly converts it back to correct structure.

Question 26

Thymine dimers-What type of DNA repair?

Answer 26

• Direct repair

- photolyase cleaves them

Question 27

Alkylated bases-What type of DNA repair?

Answer 27

• Direct repair

- alkyltransferases can fix directly

Question 28

Xeroderma Pigmentosum

Answer 28

• NER disorder
• mutation in DNA repair protein
• extremely sensitive to UV rays
• minutes in sun cause severe blistering

Question 29

Nucleotide excision repair

Answer 29

An abnormal base or nucleotide is first recognized and removed from the DNA, and a segment of DNA in this region is excised. Then the complementary DNA strand is used as a template to synthesize a normal DNA strand.

Question 30

Mismatch repair

Answer 30

The DNA defect is a base pair mismatch in the DNA. The mismatch is recognized, and a segment of DNA in this region is removed. The parental strand is used to synthesize a normal daughter strand of DNA.

Question 31

If DNA polymerase’s proofreading fails, what type of repair do you depend on?

Answer 31

mismatch repair

Question 32

Hereditary Nonpolyposis Colorectal Cancer

Answer 32

• mismatch repair disorder

- DNA repair mutations are caretaker tumor suppressors

Question 33

How are double strand breaks repaired?

Answer 33

1. homologous recombination

2. Non-homologous end joining

Question 34

Homologous recombination repair

Answer 34

• Fixes double strand breaks
• Sister chromatid used as a template
• The broken ends are eventually rejoined
• Can only happen during S and G2 phase

Question 35

Non-homologous end joining

Answer 35

• Occurs at double strand breaks
• The broken ends are recognized by proteins that keep the ends together
• The broken ends are eventually rejoined.
• Can occur in any stage of cell cycle.
• “Just sticks two pieces back together after chewing some material back.”

Question 36

Translesion synthesis

Answer 36

• uses specific polymerases that have flexible pockets to fit distorted strands
• low fidelity
• error prone replication