DNA Replication

Question 1

Is the process by which a double-stranded DNA molecule is copied to produce two identical DNA molecules.

Answer 1

DNA Replication

Question 2

• Replication of DNA
  –base pairing allows each strand to serve as a template for a new strand
  –new strand is 1/2 parent template & 1/2 new DNA

Answer 2

Semi-conservative

Question 3

is an unwound and open region of a DNA helix where DNA replication occurs.

Answer 3

Replication bubble

Question 4

Which enzyme unwinds DNA

Answer 4

Helicase

Question 5

What stabilizes the DNA helix unwound by helicase

Answer 5

single-stranded binding proteins

Question 6

Steps of DNA Replication

Answer 6

1. Unwind DNA
2. Build daughter DNA strand

Question 7

is an enzyme that synthesizes short RNA sequences called primers.

Answer 7

DNA primase

Question 8

Enzyme that relieves additional coiling during DNA replication

Answer 8

Topoisomerase

Question 9

How long are RNA primers

Answer 9

5-10 nucleotides long

Question 10

nick sealing by _________ joins new Okazaki fragment to the growing chain

“spot welder” enzyme

Answer 10

DNA ligase

Question 11

serves as starter sequence for DNA polymerase III

Answer 11

RNA primer

Question 12

removes sections of RNA primer and replaces with DNA nucleotides

Answer 12

DNA Polymerase I

Question 13

Loss of bases at 5’ ends in every replication
- chromosomes get shorter with each replication

Answer 13

Chromosome erosion

Question 14

telomere sequence in human

Answer 14

TTAGGG

Question 15

• enzyme that extends telomeres
• can add DNA bases at 5’ end
• different level of activity in different cells

Answer 15

Telomerases

Question 16

Is the enzyme responsible for maintenance of the length of telomeres by addition of guanine-rich repetitive sequences

Answer 16

Telomerase

Question 17

the number of times a normal human cell can divide before it stops dividing and enters a state of cellular senescence

Answer 17

Hayflick limit

Question 18

Holds DNA polymerase in place

Answer 18

Sliding Clamp

Question 19

Prevents the DNA double helix from getting too tightly wound as the DNA is opened up

Answer 19

Topoisomerase

Question 20

A method for amplifying DNA segments using cycles of denaturation, annealing to primers, and DNA polymerase-directed DNA synthesis

Answer 20

Polymerase Chain Reaction (PCR)

Question 21

3 Steps of performing PCR

Answer 21

1. Denaturation at 95-96°C
2. Annealing at 55-68°C
3. Elongation (Extension) at 72°C

Question 22

PCR Components:

Answer 22

1. DNA sample
2. Primers
3. Nucleotides
4. Taq polymerase
5. Mix buffer
6. PCR tube

Question 23

Machine used for PCR

Answer 23

Thermal cycler

Question 24

Step in PCR:
DNA is heated to break the hydrogen bonds between the two polynucleotide strands
–Two single-stranded DNA molecules serve as templates

Answer 24

Denaturation

Question 25

Step in PCR: Short nucleotide sequences (primers for DNA replication) are mixed with the DNA and bind to complementary regions on single-stranded DNA –Takes place at lower temperature –Primers are 20-30 nucleotides long, synthesized in the laboratory

Answer 25

Annealing

Question 26

Step in PCR: The enzyme Taq polymerase is added to synthesize a complementary DNA strand –Taq is a DNA polymerase from a bacterium found in hot springs

Answer 26

DNA Synthesis

Question 27

Process wherein a cell recognize and rectify damage to the DNA molecules

Answer 27

DNA Repair Mechanism

Question 28

Sources of DNA damage

Answer 28

– Endogenous (ROS, replication errors) – Exogenous (UV, cigarette smokes)

Question 29

Common causes of DNA damage

Answer 29

Base mismatch Single-strand break Double-strand break Interstrand crosslinks Bulky adducts/Intrastrand crosslinks

Question 30

Spontaneous alterations that require DNA repair

Answer 30

Oxidation Hydrolysis Methylation

Question 31

Release of adenine or guanine bases

Answer 31

Depurination

Question 32

Removal of amine group (NH2) ex. C to U

Answer 32

Deamination

Question 33

DNA repair mechanism for single-strand break/single base damage

Answer 33

Base-excision repair (BER)

Question 33

DNA repair mechanism for Bulky lesions/Crosslinks

Answer 33

Nucleotide excision repair (NER)

Question 33

DNA repair mechanism for base mismatch

Answer 33

Mismatch mediated repair (MMR)

Question 34

DNA repair mechanism for double-strand break

Answer 34

Homologous Recombination (HR) Non-homologous End-joining (NHEJ)

Question 35

repairs damage to a single base caused by oxidation, alkylation, hydrolysis, or deamination.

Answer 35

Base excision repair (BER)

Question 36

In BER, the damaged base is removed by a ________.

Answer 36

DNA glycosylase

Question 37

In BER, the "missing tooth" is then recognized by an enzyme called ______, which cuts the phosphodiester bond. The missing part is then resynthesized by a DNA polymerase, and a DNA ligase performs the final nick-sealing step.

Answer 37

AP endonuclease

Question 38

– recognizes bulky, cross-linking, helix-distorting lesions such as pyrimidine dimers and 6,4 photoproducts

Answer 38

Nucleotide excision repair (NER)

Question 39

– corrects errors of DNA replication and recombination that result in mispaired (but undamaged) nucleotides.

Answer 39

Mismatch repair (MMR)

Question 40

- is an autosomal recessive genetic disorder of DNA repair in which the ability to repair damage caused by ultraviolet (UV) light is deficient. - Skin cancer. - Due to failure in nucleotide-excision repair mechanism

Answer 40

Xeroderma pigmentosum

Question 41

3 steps in Mismatch Repair (MMR)

Answer 41

* Recognition (mismatches) * Degradation of error (exonucleases) * Synthesis (correct sequence)

Question 42

* Inherited disorder that increases the risk of developing colorectal cancer, endometrial cancer, ovarian cancer, etc. * Due to mutations in MMR genes

Answer 42

Lynch syndrome/Hereditary non-polyposis colorectal cancer

Question 43

– repairs oxidative damage, abasic sites, or errors of DNA topoisomerase

Answer 43

Single-strand break repair (SSBR)

Question 44

* Precise repair pathway that requires a matching DNA sequence as a template * It primarily uses the sister chromatid, a copy of the damaged DNA, for repair * Active during S, G2 and M phase

Answer 44

Homologous recombination

Question 45

* Simple and widely used mechanism * Directly seals the broken ends of DNA without the need for a homologous DNA template

Answer 45

Non-Homologous End-Joining (NHEJ)

Question 46

Significance of DNA repair

Answer 46

* Preservation of genetic information * Prevention of diseases * Protect against aging * Response to environmental stress * Contribution to the immune system (antibody diversity) * Evolution and adaptation (allows for genetic variation)