D.1.1 DNA Replication

Question 1

Purpose of DNA Replication

Answer 1

1. Mitosis - for growth and repair
   (creates 2 identical cells)
   e. Meiosis - for reproduction
   (creates 4 gametes)

Question 2

Steps of DNA Replication

Answer 2

1. Helicase unwinds DNA by breaking H bonds
   (attaches to origin of replication)
2. Gyrase and single stranded binding proteins keep strands separated
3. RNA Primase synthesises an RNA primer
4. DNA Polymerase III adds on to the RNA Primer and starts to join nucleotides through comp base pairing
   - synthesis is continuous on the 5’ to 3’ leading strand
   - synthesis is not continuous on 3’ to 5’ lagging strand
5. On the lagging strand: RNA primers are added in short intervals to allow DNA Polymerase III to synthesis the DNA is short Okazaki Fragments
6. DNA Polymerase I replaces RNA primers with DNA
7. Ligase joins the Okazaki fragments together
8. Polymerase III repairs mismatched bases
9. Final Product: 2 double stranded semi conservative DNA strands

Question 3

Enzymes involved in DNA Replication

Answer 3

1. Helicase
2. Gyrase and single stranded binding protein
3. RNA Primase
4. DNA Polymerase III
5. DNA Polymerase I
6. Ligase

Question 4

PCR stands for…

Answer 4

Polymerase Chain Reaction

Question 5

PCR process + temperatures

Answer 5

1. Denaturation separates strands (95°C)
2. Annealing adds primers to opposite ends of desired sequence (55°C)
3. Elongation (75°C)
   - Taq polymerase adds new bases and copies the strands
   - 2 new DNA strands are created

Question 6

Efficiency/usefulness of PCR

Answer 6

2 strands produced per cycle
Amounts of strands made: (cycles)^2
doesn’t take long to do a cycle so millions are made after only 20 cycles
only takes a small amount of DNA

Question 7

Purpose of PCR

Answer 7

to amplify sequences of DNA when only a small DNA sample is available
Can be then used in forensics, DNA profiling, detection of disease and detection of genetic disorders

Question 8

Purpose of Gel Electrophoresis

Answer 8

To separate DNA fragments or proteins by their size
can be used in DNA profiling

Question 9

Process of Gel Electrophoresis

Answer 9

1. DNA/protein sample is placed into the well with gel which has current passing through
2. The samples (which have a negative charge) move toward the negative electrode
3. The samples separate by size (smaller fragments move faster through the gel pores)

Question 10

What is DNA Profiling

Answer 10

The use of STRs to look for repeated patterns

Question 11

What are STRs? What is unique about them?

Answer 11

Non-coding regions of DNA that are 2-8 repetions of nucleotides
STRs are highly varied and each person will have a different repetition of STRs in their DNA
They are passed down genetically

Question 12

How can STRs be used?

Answer 12

They can be used in DNA profiling/gel electrophoresis for forensics to identify criminals or to identify parents/relatives

Question 13

Which features of DNA fragments are used to separate them in the process of gel electrophoresis?

Answer 13

Their size and charge

Question 14

Enzyme used in the polymerase chain reaction.

Answer 14

taq polymerase