When a barley seed germinates, gibberellin is released from structure A. Gibberellin diffuses to its target cells located in tissue B. This causes the cells at B to synthesise the enzyme amylase.

Figure 2.1 is a diagram of a longitudinal section through a barley seed.

On Figure 2.1, use label lines and the letters A and B to identify A, the structure where gibberellin is released, and B, the location of the target cells for gibberellin that synthesise amylase.

Draw with the mouse or a finger.

2(b)(i)Gene RegulationEasy3 marks

A gene in the cells of B is switched on so that the cells can synthesise amylase.

Figure 2.2 shows the sequence of molecular events that occurs in the cells of B during seed germination:

1
Gibberellin binds to protein C.
2
The gibberellin–protein C complex binds to protein D.
3
Protein D breaks down and releases protein E.
4
Protein E binds to DNA to allow the binding of RNA polymerase.

Identify proteins C, D and E.

Protein C

Protein D

Protein E

2(b)(ii)Gene RegulationEasy2 marks

After protein E binds to DNA, RNA polymerase can bind to DNA. Identify the region of the DNA that RNA polymerase binds to and the gene product.

Region of DNA

Gene product

2(c)Plant Responses Growth RegulatorsMedium1 mark

A variety of pea plant has a homozygous recessive genotype that prevents it from making active gibberellin.

Suggest what effect this homozygous recessive genotype will have on the height of these pea plants.