BIO 205 DNA MUTATION AND REPAIR

Question 1

sources of DNA damage

Answer 1

1. spontaneous (self-generated)

2. environmental

Question 2

SPONTANEOUS DAMAGE

Answer 2

• hydrolytic attack
• oxidative attack
• replication error

Question 3

what is hydrolytic attack

Answer 3

common food preservatives & processed foods (nitrates, nitrites)

Question 4

what is oxidative attack

Answer 4

breaks down DNA backbone

Question 5

ENVIRONMENTAL DAMAGE

Answer 5

• chemical exposure
• ionizing radiation
• UV exposure
• vaping

Question 6

examples of chemical exposure

Answer 6

tobacco, food chemicals, pollutants, chemotherapeutics

Question 7

examples of ionizing radiation

Answer 7

x-ray, gamma-ray

Question 8

UVA versus UVB

Answer 8

UVA burns skin

UVB burns DNA (2-10% reaches basal layer)

Question 9

DNA damage can lead to ___

Answer 9

mutations

Question 10

which DNA damage is passed on through generations

Answer 10

germ line

Question 11

two types of DNA damage

Answer 11

• germ line

* somatic

Question 12

germ line mutation example

Answer 12

sickle cell anemia
• genetic disease
• inherited blood disorder

Question 13

what is sickle cell anemia

Answer 13

single nucleotide change (A to T)

Question 14

somatic mutation

Answer 14

• CANNOT BE PASSED
• proliferating cancer cells
• changes of getting cancer = age correlated
• cannot be passed

Question 15

types of DNA mutations

Answer 15

point mutation, deleting, insertion, frameshift

Question 16

point mutation also called ____

Answer 16

single base substitution

Question 17

which DNA mutation is most common

Answer 17

single-base sub. / point mutation

Question 18

point mutation

Answer 18

one letter change

Question 19

deletion

Answer 19

base is removed from the DNA sequence

Question 20

insertion

Answer 20

base is inserted into the DNA sequence

Question 21

deletion/insertion not drastic when ____

Answer 21

in multiples of 3

Question 22

In insertion or deletion can cause a ________

Answer 22

frameshift mutation

Question 23

large scale damage: The four types of chromosomal mutations

Answer 23

deletions, duplications, inversions, translocations

Question 24

codons are always __ base-pairs (nucleotides) in length

Answer 24

3

Question 25

frame shift mutation

Answer 25

every nucleotide changed from error — continuing

Question 26

example of large scale damage

Answer 26

chromosome 9 and 22 SWITCH • chrom 9 derivative
• Philedelphia chrom
• Fusion product is uncontrolled
• BCR/ABL Gene fusion
results in CML (chronic myeloid leukemia)

Question 27

DNA alterations leading to mutations

Answer 27

• Damage by water
• Deamination
• Depurination
• UV radiation
• High energy radiation

Question 28

DNA alterations: damage by water

Answer 28

cleavage by addition of H2O

(hydrolysis) - leads to loss of purine

Question 29

DNA alterations: deamination

Answer 29

• hydrolysis reaction of C to T/U

* substation of one base pair for another

Question 30

DNA alterations: depurination

Answer 30

missing A or G (nothing to pair with)
• remove pair (frame shift)
• or replace unpaired

Question 31

steps in DNA repair systems

Answer 31

search, recognize, excision

Question 32

types of DNA repair systems

Answer 32

• mismatch excision repair
• nucleotide excision repair
• base excision repair
• double-strand break repair

Question 33

what DNA Polymerase is responsible for repair in eukaryotes

Answer 33

polymerase II

Question 34

MISMATCH REPAIR (MMR) summary

Answer 34

• base mismatches or small insertion/deletion loops

Question 35

how does mismatch repair work in E. COLI

Answer 35

1. mut S recognizes mismatch on nonmethylated daughter strand (temporarily unmethlyated after replication)
2. mut L binds to mut S
3. L activates H, which cleaves the unmethylated strand opposite site of methylation
4. S and L (with helicase - keeps strands separated - and exonuclease) cut out mismatched portion
5. gap filled by polymerase III, sealed by ligase

Question 36

how to know what is parent strand?

new strand?

Answer 36

• parental is methylated

* daughter strand is TEMPORARILY unmethylated after replication

Question 37

what does mismatch repair involve in E. COLI

Answer 37

mut S, mut L, mut H proteins

Question 38

mechanism of DNA mismatch repair in eukaryotes

Answer 38

newly synthesized
strand and template strand difference UNKNOWN
- new strand has nicks

Question 39

defects in mismatch repair mechanisms in eukaryotes lead to

Answer 39

hereditary colon cancer in humans

Question 40

nucleotide excision repair needed for DNA damaged by __

Answer 40

UV radiation

Question 41

harmful UV radiation effects… thymine dimer :

Answer 41

• 2 adjacent thymine bases become covalently bonded to one another - form THYMINE dimer
• creates a kink in the DNA that blocks the progression DNA polymerase
• If unrepaired, polymerase skips over the dimer, resulting in a small deletion

Question 42

Nucleotide Excision Repair (NER) used for

Answer 42

repairing thymine dimers and pyrimidine dimers

- targets bulky lesions, removes DNA on either side

Question 43

steps of nucleotide excision repair

Answer 43

1. Recognition of abnormal dimers
2. Excision of a segment (includes dimer)
3. DNA Polymerase fills gap
4. Gap sealed by DNA Ligase

Question 44

Xeroderma pigmentosum caused by

Answer 44

UV radiation

- an inherited disease that results from failure to repair pyrimidine (thymine) dimers

Question 45

high energy radiation causes

Answer 45

single & double-stranded breaks in DNA (splitting a chromosome in two)

Question 46

Xeroderma pigmentosum facts:

Answer 46

• extreme sensitivity to sunlight
• predisposition to skin cancer (8 y/o)
• recessive

Question 47

hemimethylated

Answer 47

one strand methylated