[Maximum number: 6]

During the germination of barley seeds, amylase is produced.

(a)

Describe the sequence of events that lead to the production of amylase during germination of barley seeds.

[ 3 ]

(b)

In the malting process, germination is stopped before the concentration of sugars in the germinating barley seeds exceeds a concentration that causes shoot or root growth.

Drying the germinating barley seeds at $50^{\circ} \mathrm{C}$ is one method used to stop malting.

[ 3 ]

(i)

Explain how this method would stop malting.

[ 3 ]

[Maximum number: 3]

Genes have a role in determining the overall phenotype of an organism.

(a)

Dwarf plants also occur if the genes controlling growth are not activated (switched on).

Explain how DELLA proteins act as repressors preventing gene expression.

[ 3 ]

(a)

Control of gene expression in eukaryotes is more complex than in prokaryotes.

In plants, the control of gene expression can involve plant hormones, such as gibberellin, and proteins known as JAZ and MYC.

[ 4 ]

(i)

Describe how gibberellin activates genes in plant cells.

[ 4 ]

(a)

The height of some plants is partly controlled by their genes. Height in pea plants is affected by a gene with two alleles. The dominant allele results in the production of active gibberellin, which stimulates stem elongation.

[ 4 ]

(i)

Explain how this dominant allele results in the production of active gibberellin.

[ 2 ]

(ii)

Active gibberellin stimulates stem elongation by causing the breakdown of DELLA protein repressors so that growth genes can be expressed.

Suggest the effects of the expression of these growth genes.

[ 2 ]

[Maximum number: 2]

Gibberellin is a plant growth hormone that has a role in germination and in stem elongation.

(a)

Outline how gibberellin is involved in activating genes for stem elongation.

[ 2 ]

(a)

Explain how gibberellin acts on DELLA proteins to stimulate the production of amylase in a germinating seed.

[ 6 ]