D THEME D1.1

Question 1

D1.1.1 What does “replica” mean?

Answer 1

A replica means an exact copy of something.

Question 2

D1.1.1 So what does DNA replication mean?

Answer 2

DNA replication means making an exact copy of DNA.

Question 3

D1.1.1 In DNA replication, what must be identical?

Answer 3

The base sequence of the DNA strand—A, T, G, and C—must be copied exactly in the new strand.

Question 4

D1.1.1 When DNA is copied, what is made?

Answer 4

Two identical DNA molecules are made, called “daughter molecules” or “sister molecules.

Question 5

D1.1.1 So what do these daughter cells receive?

Answer 5

Each daughter cell receives a complete genome—this means all the DNA instructions.

Question 6

D1.1.1 How do unicellular organisms divide?

Answer 6

They divide through a process called binary fission, which is a type of cell division.

Question 7

D1.1.1 Why does cell division happen in multicellular organisms?

Answer 7

GRR – for Growth (more cells for body size), Reproduction (producing gametes), and Replacement (fixing damaged tissues).

Question 8

D1.1.2 DNA begins replication by?

Answer 8

Unzipping its strand, via the weak hydrogen bonds that exist, enables it to be split apart.

Question 9

D1.1.2 Each strand acts as a template to form?

Answer 9

A new strand, so each DNA strand acts for another strand to be replicated

Question 10

D1.1.2 What occurs with bases?

Answer 10

Bases are shown to bind to this template and begin binding to form a new strand.

Question 11

D1.1.2 Specifically, it helps build?

Answer 11

New polymers of nucleotides.

Question 12

D1.1.2 This process of DNA replication is called?

Answer 12

Semi-conservative replication, as each half of the DNA is specially replicating and making a new strand of DNA.

Question 13

D1.1.2 The DNA replication afterwards is described as?

Answer 13

Being genetically identical—exactly the same copies

Question 14

D1.1.2 No information has been?

Answer 14

Been lost nor changed.
It’s conserved.

Question 15

D1.1.2 Why is DNA genetically identical?

Answer 15

DNA is genetically identical due to the ruling of Chargaff’s base pairing rules.

Question 16

D1.1.2 DNA is genetically identical due to complementary?

Answer 16

Base pairing having genetically identical pairs.

Question 17

D1.1.2 Due to complementary base pairing, what’s rare?

Answer 17

The rate of mutation, therefore it’s genetically identical.

Question 18

D1.1.3 What is DNA described as when replicating?

Answer 18

It looks like a DNA fork, which has a Y shape. This shows how the hydrogen bonds break for DNA replication to begin.

Question 19

D1.1.3 As DNA replication continues, what happens?

Answer 19

The remaining part of the DNA begins to split so replication can continue.

Question 20

D1.1.3 What helps in DNA replication?

Answer 20

Two main enzymes are very important in this process.

Question 21

D1.1.3 What are the two enzymes and what do they do?

Answer 21

Helicase: an enzyme that unwinds the DNA by breaking hydrogen bonds.
DNA polymerase: an enzyme that builds new strands of DNA by using the old strands as templates.

Question 22

D1.1.3 Why is DNA described as semi-conservative?

Answer 22

Because each new DNA molecule has one old strand and one new strand.

Question 23

D1.1.3 What are the two new strands like?

Answer 23

They are genetically identical to each other and to the original strand.

Question 24

D1.1.3 What causes the two strands to be identical?

Answer 24

Complementary base pairing (A pairs with T, G pairs with C).

Question 25

D1.1.3 What happens in Stage 1 of DNA replication?

Answer 25

DNA is split in half by the enzyme helicase, which breaks the weak hydrogen bonds.

Question 26

D1.1.3 What happens in Stage 2 of DNA replication?

Answer 26

DNA polymerase forms the new DNA strands by matching bases to the template strands (A–T and G–C).

Question 27

D1.1.3 What happens after DNA replication?

Answer 27

The new DNA molecules rewind into their double helix structure.

Question 28

D1.1.4 What happens after each round of PCR?

Answer 28

The amount of DNA doubles.

Question 29

D1.1.4 What is this process called?

Answer 29

DNA amplification.

Question 30

D1.1.4 How many rounds and how long does it take for PCR ?

Answer 30

30 to 40 rounds, taking around 2 to 3 hours.

Question 31

D1.1.4 What is the result by the end FOR PCR?

Answer 31

A large amount of DNA is produced, stored inside a small Eppendorf tube

Question 32

D1.1.4 PCR relies on

Answer 32

Repeated cycles of temperature changes in the thermocycler.

Question 33

D 1.1.4 What does this process do GEL ELECTRO?

Answer 33

It sorts molecules (like DNA or proteins) based on their overall charge.

Question 34

D1.1.4 How is the sample added?

Answer 34

A small amount of liquid is pipetted into wells on one side of the machine (the gel tray).

Question 35

D1.1.4 What does the gel do?

Answer 35

The gel (usually made from agarose) acts like a net. It slows down or blocks large or certain molecules from moving through easily.

Question 36

D1.1.4 What is applied to move the molecules?

Answer 36

Electricity – electrodes are placed at both ends to create an electric field.

Question 37

D1.1.4 What happens during gel electrophoresis?

Answer 37

Charged molecules move towards the oppositely charged electrode (negative to positive, and vice versa).

Question 38

D1.1.4 What happens to DNA in this process?

Answer 38

DNA moves towards the positive electrode (called the anode) because it is negatively charged due to its phosphate groups.

Question 39

D1.1.4 So where is the DNA loaded?

Answer 39

On the cathode side (negative end), so it can travel towards the anode (positive end).

Question 40

D1.1.4 As the agarose causes a gel-like mesh, what happens?

Answer 40

Some small components of DNA pass through easily, while the larger sections struggle to move through the mesh.

Question 41

D1.1.4 What is gel electrophoresis?

Answer 41

It’s a size-dependent method—smaller sections of DNA move faster than larger ones.

Question 42

D1.1.4 When is the electricity switched off?What else is done when electricity is added?

Answer 42

The electricity is switched off when the smallest DNA fragments have nearly reached the end of the gel (the anode side). DYE

Question 43

D1.1.4 What do molecules of the same size and position do?

Answer 43

They bunch up together and form a distinct band or line on the gel.

Question 44

D1.1.4 Where are many DNA samples loaded?

Answer 44

They are loaded into parallel lanes across the gel, allowing for comparison of different samples side by side.

Question 45

D1.1.4 Gel electrophoresis is also very good for sorting short tandem repeats (STRs), what are STRs?

Answer 45

A Short tandem repeats located in specific regions of chromosomes, where a short DNA sequence repeats itself.

Question 46

D1.1.4 the amount of times it’s repeated STRs is is specific for a person

Answer 46

A Varies for every individual. For example, at chromosome 7, some people may have more STR repeats than others. The band length on the gel changes depending on the number of repeats.