Exam 3 (Topic 13)

Question 1

Single nucleotide change in the hemoglobin gene

Answer 1

Sickle-cell Anemia

Question 2

Causes aggregation of hemoglobin and abnormal cell shapes

Answer 2

Sickle-cell Anemia

Question 3

Makes a mismatch ever 10^7 base copied

Answer 3

DNA polymerase

Question 4

Fixes 99% of mismatched base copies

Answer 4

DNA mismatch repair

Question 5

Mismatch repairs can only be done on

Answer 5

newly synthesized DNA strand

Question 6

DNA mismatch repair mechanism

Answer 6

1. DNA mismatch repair enzyme binds to the mismatch site
2. DNA mismatch repair proteins remove the newly synthesized strand
3. DNA polymerase fills the gap
4. DNA ligase joins the new fragments together

Question 7

Spontaneous loss of the amino group from cytosine which produces uracil (c –> u) mutation

Answer 7

Deamination

Question 8

Loss of purine bases (A and G) from the deoxyribose-phosphate backbone

Answer 8

Depurination

Question 9

UV light can form covalent bonds between two thymine nucleotides on the SAME strand

Answer 9

Thymine dimer (DNA damage)

Question 10

Can cause mutations, terminate DNA replication, or cause DNA polymerase to stall

Answer 10

Thymine dimer

Question 11

All types of damage result in either ___________ or _______________.

Answer 11

mutations in the genetic code or inhibition of DNA replication completely

Question 12

DNA Repair Mechanism

Answer 12

1. The damage DNA is recognized and removed by nucleases
2. A repair DNA polymerase fills the gap
3. DNA ligase rejoins the break in the phosphate backbone

Question 13

Enzyme that removed nucleotide

Answer 13

nuclease

Question 14

Mutation in NER (nucleotide excision repair) enzymes

Answer 14

Xeroderma Pigmentosum (XP)

Question 15

Children of the night

Answer 15

XP

Question 16

Radiation, Torsional stress from replication, and strong oxidizing agents can cause

Answer 16

DNA undergoes double strand breaks

Question 17

Most common type of DSB repair in somatic cells (non-sex cells)

Answer 17

Non-homologous end-joining

Question 18

Non-homologous end-joining Mechanism

Answer 18

1. Two broken ends are processed and cut by nuclease (lose sequence)
2. Then DNA ligase rejoins the DNA
   DOES NOT SYNTHESIZE NEW DNA

Question 19

Repairs double stranded breaks without losing sequence (method of choice for stem or sex cells)

Answer 19

Homologous Recombination

Question 20

Homologous Recombination Mechanism

Answer 20

1. A nuclease digests the 5’ ends of the double stranded break
2. A single DNA strand invades the homologous DNA complex (strand invasion complementary)
3. Using the homologous DNA as a template, repair DNA polymerase creates new DNA
4. Repair is completed by DNA ligase closing the gaps