A Unity and Diversity

A1.1 Water

A1.2 Nucleic acids

A2.1 Origins of cells

A2.2 Cell structure

A3.1 Diversity of organisms

A4.1 Evolution and speciation

A4.2 Conservation of biodiversity

B Form and Function

B1.1 Carbohydrates and lipids

B1.2 Proteins

B2.1 Membranes and membrane transport

B2.2 Organelles and compartmentalization

B2.3 Cell specialization

B3.1 Gas exchange

B3.2 Transport

B4.1 Adaptation to environment

B4.2 Ecological niches

C Interaction and Interdependence

C1.1 Enzymes and metabolism

C1.2 Cell respiration

C1.3 Photosynthesis

C2.2 Neural signalling

C3.1 Integration of body systems

C3.2 Defence against disease

C4.1 Populations and communities

C4.2 Transfers of energy and matter

D Continuity and Change

D1.1 DNA replication

D1.2 Protein synthesis

D1.3 Mutation and gene editing

D2.1 Cell and nuclear division

D2.3 Water potential

D3.1 Reproduction

D3.2 Inheritance

D3.3 Homeostasis

D4.1 Natural selection

D4.2 Stability and change

D4.3 Climate change

IB Biology SL D1.1 DNA replication Question Bank

[Maximum number: 1]

Which diagram(s) illustrate(s) semi-conservative replication of DNA?

X only

Y only

Z only

X and Y only

[Maximum number: 5]

Over 50 years ago, Meselson and Stahl investigated the mechanism of DNA replication. They transferred a rapidly growing population of Escherichia coli from a growth medium containing only ${ }^{15} \mathrm{~N}$ to a growth medium with only ${ }^{14} \mathrm{~N}$ . DNA samples were centrifuged at high speed in a salt density gradient. In the original published research, DNA molecules of the same density appear as a band in the UV absorption photographs as shown.

Generations

(a)

Explain the pattern shown in generation 3.0.

[ 3 ]

(b)

This experiment was designed to demonstrate whether replication was semi-conservative or conservative. Distinguish between semi-conservative replication and conservative replication.

[ 2 ]

[Maximum number: 1]

What bonds do the enzymes DNA polymerase and helicase form or break during DNA replication?

DNA polymerase

Helicase

forms sugar-phosphate bonds

breaks hydrogen bonds

forms hydrogen bonds

breaks sugar-phosphate bonds

forms hydrogen bonds

forms sugar-phosphate bonds

forms hydrogen bonds

[Maximum number: 1]

The diagram shows a gel electrophoresis apparatus.

What can be deduced from the diagram?

X is the smallest fragment.

Y is positively charged.

X is moving towards the cathode.

Y travels at the greatest rate.

[Maximum number: 1]

Meselson and Stahl conducted experiments using the isotopes ${ }^{14} \mathrm{~N}$ and ${ }^{15} \mathrm{~N}$ which showed that DNA replication is semi-conservative. What would they have observed about the distribution of isotopes in the DNA after one round of replication if DNA replication was conservative rather than semi-conservative?

Only ${ }^{14} \mathrm{~N}$ DNA

Only ${ }^{15} \mathrm{~N}$ DNA

All DNA half ${ }^{14} \mathrm{~N}$ and half ${ }^{15} \mathrm{~N}$

Half the DNA with only ${ }^{14} \mathrm{~N}$ and half with only ${ }^{15} \mathrm{~N}$

[Maximum number: 1]

The percentage of cytosine in the genome of the common octopus (Octopus vulgaris) is 17.6 %.

(a)

Scientists can amplify DNA molecules and separate mixtures of DNA molecules in the laboratory for analysis.

State the laboratory method used to amplify DNA.

[ 1 ]

[Maximum number: 1]

What occurs during DNA replication?

DNA polymerase separates the two DNA strands.

DNA molecules containing nucleotides from the original molecule are produced.

Adenine forms a base pair with either thymine or uracil.

New bases attach to the original sugar-phosphate backbone.

[Maximum number: 1]

Which are necessary to make DNA replication semi-conservative?

I. Separation of the strands by RNA polymerase
II. Complementary base pairing
III. Use of a pre-existing strand as a template

I and II only

I and III only

II and III only

I, II and III

[Maximum number: 1]

What is required to replicate DNA?

Temperature of $37^{\circ} \mathrm{C}$

Free nucleotides carrying A, C, G and T bases

Plasmids

Endonuclease

[Maximum number: 1]

Bacteria cultured in a medium containing only ${ }^{15} \mathrm{~N}$ were transferred to a medium containing only ${ }^{14} \mathrm{~N}$ and allowed to complete one round of replication. The DNA in bacteria produced as a result of replication on the ${ }^{14} \mathrm{~N}$ medium was extracted and subjected to caesium chloride centrifugation which separates DNA molecules according to their density.

Which centrifuge tube shows the arrangement of bands observed after one round of replication?

Tube 3

Tube 4

Tube 5

Tube 6

0 selected

Question 6

Question 2

Question 2(c)

Question 2(d)

Question 7

Question 7

Question 8

Question 2

Question 2(b)

Question 9

Question 9

Question 9

Question 10