Replication of DNA

Question 1

What is DNA replication?

Answer 1

DNA replication is the process by which a cell makes an identical copy of its DNA

Question 2

When is the process of DNA replication performed and why is it done at that time?

Answer 2

The process of DNA replication is performed at the beginning of every cell division, so that when division occurs each daughter cell will inherit an identical copy of the DNA

Question 3

What is responsible for the sugar-phosphate bonding of nucleotides?

Answer 3

DNA polymerase

Question 4

How doe the process of DNA replication begin?

Answer 4

DNA replication begins with the double helix unwinding itself (with the help of an enzyme), breaking the weak hydrogen bonds, this allows the DNA strands to separate (sometimes referred to as “unzipping”)

Question 5

What is the shape and name of the area of separation?

Answer 5

It is a Y-shape, this area called a replication fork

Question 6

What does the separation of the DNA do that is necessary?

Answer 6

It exposes the induvial bases

Question 7

What does DNA replication require?

Answer 7

An enzyme called polymerase

Question 8

Under what circumstance can the polymerase enzyme add new nucleotides to a strand of DNA?

Answer 8

When a chain has already been started and when a primer is present

Question 9

What is a primer?

Answer 9

Primers are short complementary strands of nucleotides that allow DNA polymerase to bind

Question 10

What does each strand of parental DNA act as?

Answer 10

A template against which another DNA strand can be formed from free DNA nucleotides present in the nucleus

Question 11

How does the now separated strand become a full copy of its parental DNA?

Answer 11

Once the bases are exposed, the nucleotides form weak hydrogen bonds with the corresponding bases, then once all the necessary amount of hydrogen bonds have been formed, the nucleotides together form a strong sugar-phosphate bond

Question 12

What is replication of parental strand, and what does it form?

Answer 12

Replication of the parental strand is continuous and forms what is known as the leading strand in DNA replication

Question 13

What is the only direction that polymerase can add nucleotides in?

Answer 13

3’ to 5’ direction

Question 14

How is the lagging strand of DNA formed into a full complementary strand?

Answer 14

Primers are added on by one onto the lagging strand, DNA nucleotides are added in fragments, these fragments are joined together by DNA ligase to form a complete complementary strand

Question 15

What does the lagging strand formation require?

Answer 15

ATP produced via the cell’s respiration

Question 16

What is PCR?

Answer 16

Polymerase chain reaction, it is a laboratory technique that is used to amplify target sequences of DNA

Question 17

What is ligase?

Answer 17

A type of enzyme that join nucleotide fragments together

Question 18

What does vitro mean?

Answer 18

Vitro is when something happens outside the body of the organism in laboratory apparatus

Question 19

What is the basic idea behind PCR?

Answer 19

PCR exposes DNA to a series of temperature changes, known as thermal cycling

Question 20

What does the process look like?

Answer 20

The DNA is exposed to extreme heats of 90+ Celsius to denature the DNA which separates the strands. It is then cooled to between 50 and 65 to allow complementary primers to bind to specific target sequences. The heat is then raised to between 70 and 80 when heat tolerant polymerase is used to synthesise new strands from free DNA nucleotides. These steps are automated and repeated to allow billions of copies of the target sequence to be produced

Question 21

What four things does DNA replication require and why?

Answer 21

Original DNA template - used as a template on which new DNA can be created, free DNA nucleotides - needed to form the new strands, DNA polymerase - an enzyme that adds new nucleotides to a growing strand of DNA, Primers - a primer is a short strand of nucleotides that will bind to 3’ end of the template allowing DNA polymerase to add new free DNA nucleotides

Question 22

How is the leading strand formed?

Answer 22

It is synthesised continuously, polymerase adds nucleotides to the deoxyribose (3’) in a 5’ to 3’ direction

Question 23

What is required for PCR?

Answer 23

Stream of free nucleotides, thermal cycler, heat tolerant polymerase, strand of DNA wanting to be copied and complimentary primers