DNA Replication & Repair

Question 1

Base pair allows for ________

Answer 1

DNA Replication

Question 2

Each strand of DNA that contains a certain type of nucleotide sequence can be a ______ used to make a new strand

Answer 2

Template (allows cells to replicate genes before dividing up)

Question 3

Semiconservative replication

Answer 3

Since each parent strand of DNA is a template for each daughter strand of DNA double helix, the duaghter helix will have one of the parent strand (old strand strand) & a new strand

Question 4

DNA synthesis begins at ______

Answer 4

Replication origins

Question 5

Replication origins

Answer 5

Specific DNA sequence that initiator proteins bind to start DNA synthesis (unzip/ open up a DNA strand & its just an area where DNA is opened)

Question 6

__________ form at each replication origin

Answer 6

Two replication forks

Question 7

Replication fork

Answer 7

The y shaped junctions that allows a replication machine to move along the DNA (they continuously open DNA strands up in opposite direction)

Question 8

__________ synthesizes DNA using a parental strand as a template

Answer 8

DNA polymerase (is whats copying the DNA strands as the replication forks is continuously opening up the DNA strand)

Question 9

DNA polymerase 3

Answer 9

An enzyme that builds the new strand of DNA using the old strand as a template (Builds it in the 5’ to 3’ direction)

Question 10

The new DNA strand is made (synthesized) in what direction by the DNA polymerase?

Answer 10

The DNA polymerase makes the new DNA strand in the 5’ to 3’ direction only (add a new nucleotide triphosphate)

Question 11

The replication fork is ________ because at each replication fork one new DNA strand is made on a template that runs in 3’ to 5’ direction whereas the other new DNA strand is made in the 5’ to 3’ direction

Answer 11

Asymmetrical

Question 12

Okazaki Fragments

Answer 12

Small DNA pieces that was made in the opposite direction of the replication fork (made in the 3’ to 5’ direction) & is made disconinuously, they ae the lagging strands

Question 13

Lagging strand

Answer 13

The DNA strand that is made discontinuously

Question 14

Leading strand

Answer 14

The DNA strand that made continuously

Question 15

Since DNA polymerase only goes in the 5’ to 3’ direction it is able to be ________

Answer 15

Self - Correcting

Question 16

What are the two reasons why DNA is able to be self-correcting and make no wrong base pairs (like A-G or C-T) ?

Answer 16

1. The enzyme (DNA polymerase) carefully monitors the base-pairing between each incoming nucleotide triphosphate & template strand
2. When DNA polymerase does make a rare mistake & add wrong base pairs togethers it can correct it through proofreading

Question 17

________ occurs as each new DNA strand is made

Answer 17

Proofreading

Question 18

Short lengths of _______ act as primers for DNA synthesis

Answer 18

RNA

Question 19

Primers

Answer 19

A Short nucleic acid sequence that provides a starting point for DNA synthesis

Question 20

The accuracy of DNA replication depends on the _________ to correctly base - pair the 3’ end before adding on more nucleotides

Answer 20

DNA polymerase

Question 21

Primase

Answer 21

An enzyme that is used as a starting place to make a new strand of DNA, its made of a short RNA & uses the DNA strand as the template since the A in DNA can pair with the U in RNA the RNA fragment serves as a primer (Starting place) for DNA synthesis (Its a type of RNA polymerase)

Question 22

RNA contains ______ instead of thymaine (T) but since _____ can pair with A, RNA primer is made on the DNA strand by base - pairing the same way as DNA

Answer 22

Uracil (U)

Question 23

_________ only starts the replication at the replication origins

Answer 23

RNA primer

Question 24

Need _______ to form a new strand of DNA from the lagging strands

Answer 24

DNA Ligase

Question 25

DNA ligase

Answer 25

An enzyme that joins the 5' end phosphate of one okazi fragment to the adjacent 3' end hydroxyl end of the next (Seals the gap within the strands)

Question 26

\_\_\_\_\_\_ at a replication fork cooperate to form a replication machine

Answer 26

Proteins

Question 27

What protein (enzyme) continuously open/unzip DNA strand?

Answer 27

DNA helicases

Question 28

DNA helicases

Answer 28

An enzyme that breaks the hydrogen bond between the base

Question 29

Single-strand DNA-binding proteins

Answer 29

Prevents the DNA strand from zipping up back up

Question 30

DNA topoisomerases

Answer 30

Enzyme that relase the tension caused by the helicases continuously prying open DNA causing it to twist even more

Question 31

\_\_\_\_\_\_\_\_ produces a single-strand cut in the DNA backbone which releases the tensions

Answer 31

DNA topoisomerase

Question 32

\_\_\_\_\_\_\_\_\_ replicates the ends of eukaryotic chromosomes

Answer 32

Telomerase

Question 33

Telomerase

Answer 33

Are enzymes attached to the end of a chromsome

Question 34

Telomerase uses its own _________ template which it uses to add multiply copies of repetitive DNA sequence to the lagging - strands so the lagging strand doesn't get shorter & shorter so that DNA isn't lost in each cell divison

Answer 34

RNA template

Question 35

\_\_\_\_\_\_\_\_ & __________ prevents linear eukaryotic chromosomes from shortening with each cell division

Answer 35

Telomers & telomerase

Question 36

DNA damage occurs in cells since DNA molecules undergo _____ with other molecules

Answer 36

Collisions

Question 37

Depurination

Answer 37

Process where purine bases (A & G) is lost from DNA in the cells of the body (Just removes the purine bases)

Question 38

Deamination

Answer 38

Loss of a an amino group from a cytosine in DNA to produce the base Uracil

Question 39

Thymine dimer

Answer 39

Type of damage to DNA by UV radiation from the sun which causes covalent linkage between two adjacent pyrimidine bases

Question 40

What are the different types of chemical changes?

Answer 40

1. Depurination 2. Deamination 3. Thymine dimer

Question 41

If chemical modification are left unpaired it can cause \_\_\_\_\_\_\_\_\_

Answer 41

Mutations

Question 42

What are the steps for repairing DNA?

Answer 42

1. When the damage is recognized, nucleases will cut out the damage nucleotide sequence from the DNA strand leaving a gap on the strand 2. A repair DNA polymerase binds the 3' hydroxyl end of the cut DNA strand where the enzyme fill up the gap by making a complementary copy of the nucleotide sequence in the damage strand 3. When the repair DNA polymerase filled up the gap the break in the sugar-phosphate backbone is fixed by DNA ligase

Question 43

A DNA _______ system removes replication errors that escape proofreading

Answer 43

Mismatch repair system

Question 44

Mismatch repair

Answer 44

Corrects the mistakes that were left after proofreading

Question 45

Mismatch

Answer 45

Mispaired nucleotide (like A-G or C-T)

Question 46

If nucleotides on one strand of DNA is damaged it can be fixed using \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

Answer 46

Nucleotide sequence in the complementary strand as a template

Question 47

What are the strategies used to repair double-strand break?

Answer 47

1. Nonhomologous end joinging 2. Homologous Recombination

Question 48

Nonhomologous end joining

Answer 48

Sticking the broken ends back together before the fragment drift apart but also can lose nucleotides at the repair site as well (Risky process)

Question 49

Homologous Recombination

Answer 49

Flawlessly repairs DNA double -strand break (safer process)

Question 50

What is the steps for homologous steps?

Answer 50

1. Nuclease digest the 5' end of the broken strand 2. Strand invasion by complementary base-pairng 3. Repair polymerase synthsizes DNA using undamaged complementary DNA as a template 4. Invading strand released complementary base-pairing allows broken helix to reform 5. DNA synthesis using complementary strands from damaged DNA as a template 6. DNA ligation

Question 51

SSB proteins

Answer 51

Protect the two separated DNA strand & stablize them which prevent them from snapping back together

Question 52

DNA replication occurs where in eukaryotic cell?

Answer 52

In the nucleus

Question 53

DNA polymerase 1

Answer 53

Removes the primer from the lagging strand and replaces it with DNA (Move in the 5' to 3' direction & have exonuclease activity which has a role in DNA repair)