Module 6, section 1: Cellular control.

What are the three ways gene expression can be controlled?

At the transcriptional, post transcriptional and translational level.

What affects the shape of transcription factors?

Specific molecules present in the environment, like hormones and sugars, which affect how it bonds the the dna. In this way, certain molecules affect protein synthesis.

What do transcription factors bind to in prokaroytes?

Operons.

What are operons?

A cluster of genes that transcription factors bind to to either inhibit or activate transcription.

Describe how the lac operon changes in response to presence of lactose.

1. Usually, the lac repressor is bound to the operator section of the dna, thus preventing trasncription.

2. When lactose is present, it binds to the lac repressor, thus removing the lac repressor from the operon so it can undergo transcription.

Why are mrna strands edited? What are these individual parts called? What is the final product called?

There are genes present that dont code for amino acids, and they are removed. These sections of dna are called introns.

The final product is called mature mRNA.

Describe how post translational control can occur, using cAMP as an example.

After translation, not all proteins are functional, sometimes requiring substances to bind to them to activate them.

cAMP binds to PKA’s subunits, causing a change in the 3d structure of the enzyme, meaning it is now active.

What are homeobox and hox genes?

1. Homeobox genes are involved in the development of an embyro.

2. Hox genes are a type of homeobox gene that controls body plans, the general physical structure of an organism.

Describe the role of the homeodomain.

Transcription factor that binds to DNA at start of developmental genes, thus activating or repressing the production of proteins needed for the development of a body plan.

Describe the steps of apoptosis.

1. Membrane bound organelles containing enzymes break down.

2. Cell breaks down and begins to fragment

3. Phagocyte engulfs the cell fragments.

Describe some examples of apoptosis in development.

1. During the development of the fetus, the digits of the fetus are connected by tissue. This tissue is broken down via apoptosis to prevent pain.

2. When tadpoles develop, their tails are removed via apoptosis.

3. In the development of the nervous system, the surplus neurones are removed via apoptosis.

What can affect mitosis and apoptosis?

Pathogenic attack, stress, poor diet etc.