D1.1 DNA Replication

Question 1

State that DNA replication is the production of exact copies of DNA with identical base sequences.

Answer 1

DNA replication → production of exact copies of DNA with identical base sequences

Question 2

Outline the purposes of DNA replication.​

Answer 2

Growth and tissue replacement in multicellular organisms
Reproduction

Question 2

Explain the role of complementary base pairing in DNA replication.

Answer 2

Due to complementary base pairing, DNA replication is highly accurate due to complementary base pairing

Question 2

Describe the meaning of “semi conservative” in relation to DNA replication.

Answer 2

Both new strands have a parent strand from original DNA and one newly synthesized strand

Question 3

State why DNA strands must be separated prior to replication.

Answer 3

Allow the primer and polymerase to attach to the single strand

Question 4

Outline the role of helicase in DNA replication.

Answer 4

Unwinds the DNA double helix by breaking hydrogen bonds between complementary nucleotides.

Question 5

Outline the role of DNA polymerases in DNA replication.

Answer 5

Moves along each strand of DNA linking nucleotides to form a growing chain of nucleotides using pre-existing strand as a template

Question 5

State that there are separate DNA polymerases for each stand of template DNA.

Answer 5

Each strand of DNA has its own DNA polymerase

Question 6

State the function of the PCR.

Answer 6

Amplify a DNA sequence from a small sample

Question 7

Outline the process of the PCR, including the use of primers, temperature changes and Taq polymerase.

Answer 7

Denaturation : DNA sample heated to 95 C to break h - bonds and separate two DNA strands
Annealing : Temperature reduced to 54 C allows DNA primers to bind to both strands of DNA, next to the sequence that needs copied
Temperature increased to 72 C allowing Taq DNA polymerase to replicate both strands, starting at the primer, producing two identical double stranded DNA molecules.
Steps 1-3 repeated to produce many more copies of DNA

Question 8

Outline the procedure for DNA electrophoresis.

Answer 8

Restriction enzymes cut DNA at specific sequences
Due to different individuals having different DNA, the location of restriction sites varies
Meaning each individual will have different sized fragments.
The fragments is then in wells in an agarose gel
Gel is located in a buffer filled chamber with a positive and negative side. DNA is located on the negative side
When the chamber is turned on DNA fragments will move to the positive side, at different speeds, smaller fragments moving faster and further within a given time

Question 9

Describe how and why DNA fragments separate during electrophoresis.​ ​

Answer 9

Because the DNA fragments vary in size the smaller fragments moving faster and thus farther within a given time.

Question 10

List applications of the PCR.

Answer 10

Forensic investigations
Paternity testing

Question 11

Outline the use of the PCR in testing for viral infection.

Answer 11

Can be used to detect viral infections

Question 12

Discuss advantages and disadvantages of using the PCR test for viral infections.

Answer 12

Advantages
High sensitivity and specificity
Multiplexing multiple viruses can be detected per test.
Disadvantagess
Long turnaround times for results
False positives can be yielded if samples aren’t collected at right times

Question 13

Outline the process of DNA profiling.

Answer 13

Collect: Obtain DNA sample.
Amplify: Use PCR to copy DNA.
Separate: Analyze DNA fragments by size using gel electrophoresis
Count: Determine repeat units.
Match: Compare for identification.

Question 14

List applications of DNA profiling.

Answer 14

Used to determine paternity

Question 15

State that DNA polymerases can only add free nucleotides to an existing DNA strand.

Answer 15

DNA polymerase can only add free nucleotides to existing DNA strands

Question 16

List example sources of DNA that can be used in DNA profiling.​

Answer 16

Hair, Blood, Saliva, Semen

Question 17

State that DNA polymerases can only add the 5’ phosphate of a free nucleotide to the 3’ deoxyribose of the elongating strand.

Answer 17

DNA polymerases can only add the 5’ phosphate of a free nucleotide to the 3’ deoxyribose of the elongating strand.

Question 18

Explain why replication is different on the leading and lagging strands of DNA.

Answer 18

Because the polymerase on the lagging strand moves away from the replication fork

Question 18

Compare the pace and direction of replication on the leading and lagging strands of DNA.

Answer 18

The leading strand’s DNA replication is continuous and the lagging strand is discontinuous
The leading strand’s DNA replicates towards the replication fork
The lagging strand moves away from the replication form

Question 19

Outline the formation of Okazaki fragments on the lagging strand.

Answer 19

Due to the lagging strand polymerase moving away from the replication fork, the lagging strand has multiple fragments of DNA called Okazaki fragments.

Question 20

Explain the need for RNA primers in DNA replication.

Answer 20

RNA primers attaches to the template strand allowing the polymerase to attach itself

Question 21

Outline the function of the enzyme DNA primase.

Answer 21

Attaches small RNA primers to template strand

Question 22

Compare the number of RNA primers on the leading and lagging strands.

Answer 22

One RNA primer on leading strand
RNA primers placed at intervals on lagging strand

Question 23

Outline the function of the enzyme DNA polymerase III.

Answer 23

Assemble new strands of DNA by placing free nucleotides in the correct sequence according to the base sequence of the template strand. Only able to build strands in 5’ to 3’ direction.

Question 24

Outline the function of the enzyme DNA polymerase I.

Answer 24

Removes RNA nucleotides of primers and replaces them with correct DNA nucleotides

Question 25

Outline the function of the enzyme DNA ligase.

Answer 25

To connect Okazaki fragments

Question 26

Explain why there are gaps between adjacent Okazaki fragments on the lagging strand.

Answer 26

Because the polymerase III adds nucleotides in the opposite direction of the replication fork meaning it reaches the end of the strand.

Question 27

State the function of DNA proofreading.

Answer 27

To correct mismatched bases

Question 28

Outline the process of DNA proofreading by DNA polymerase III.

Answer 28

As the newly formed DNA is being built, if a nucleotide is placed with a mismatched base, an incorrect nucleotide is removed and replaced with a correctly matching one.