Gene Regulation

Gene Regulation

by Mr. Cavida

​DNA and Cell Function

• DNA is in every cell

• mRNA only copies DNA genes that are useful to the cells

• cell function is dependent on the proteins produced

  • ​pancreas - insulin

  • ​blood cell - haemoglobin

  • ​stomach - HCl

  • ​salivary gland - saliva

Open Ended

Explain the importance of gene regulation.

​Terminology:

• ​Gene - a section of DNA that code for polypeptides and functional RNA and are located at a fixed locus on a DNA molecule.

• ​DNA - is used to give instructions for the production of proteins in the process of protein synthesis.

​Terminology:

• ​Gene Regulation - is the process of controlling which genes in a cell's DNA are expressed (used to make a functional product such as a protein).

​Ways Genes are Regulated

• ​Gene regulation can occur at any point during gene expression, but most commonly occurs at the level of transcription (when the information in a gene's DNA is passed to mRNA).

​Ways Genes are Regulated

• Rate of mRNA Synthesis (Transcription) - There are proteins that can bind to certain gene regions to increase the rate of transcription, like the transcription enzyme RNA Polymerase.

​Ways Genes are Regulated

• mRNA degradation - There are proteins that can bind to certain gene regions to decrease transcription to the point that it may not transcribed at all.

Multiple Choice

Why are cells in the skeletal system sturdy, where as skin cells are soft and stretchy?

• due to the specific proteins that are synthesized (made) by specific cells

• due to underlying mutations and specifications of the DNA

• due to DNA

Multiple Choice

What functions as the on off switch for mRNA transcription

• transcription factors

• translation factors

• transgenic factors

​When and why genes are expressed

• ​Expressed all the time

  • ​genes responsible for routine, continuous metabolic functions (for example, respiration), common to all cells, continuous throughout life

​When and why genes are expressed

• ​Expressed at a selected stage in cell or tissue development

  • ​as cells derived from stem cells are developing into muscle fibres or neurones, for example

​When and why genes are expressed

• ​Expressed only in the mature cell

  • ​genes responsible for antibody production in a mature plasma cell, after these have been cloned

​When and why genes are expressed

• ​Expressed on receipt of an internal or external signal

  • ​when a particular hormone signal, metabolic signal, or nerve impulse is received by the cell, such as the gene for insulin production in β cells in the islets of Langerhans

Open Ended

Why and when genes are expressed?

​How is this gene regulation brought about?

• ​Regulation of gene action is partly regulated by the genes themselves

• ​Many genes code for specific enzymes or proteins required by working cells at some stage.

• ​Other genes regulate other gene.

​Two Categories of Genes

• ​Structural genes

  • ​code for a structural protein, or an enzyme, or an RNA molecule not involved in regulation

  • ​required by cells to create or maintain the structure, or enable the functioning, of the cell or organism

  • ​transcribed into proteins

​Two Categories of Genes

• ​Regulatory genes

  • ​involved in controlling the expression of one or more genes

  • ​may code for a protein or for an RNA molecule

​Two Categories of Enzymes

• ​Genes are also regulated by ‘signals’ from the environment – typically from within the cell.

• These act on the enzymes or on the genes that code for them.

​Two Categories of Enzymes

• ​Inducible enzymes

  • ​produced under specific conditions, such as the presence of a particular substrate

  • ​controls the expression of one or more genes, structural genes, involved in the metabolism of that substance

  • ​in the absence of the substrate, gene action is switched off

​Two Categories of Enzymes

• ​Repressible enzymes

  • ​generally produced continuously, but their production can be halted

  • ​formed unless a signal, such as an excess of product, turns their production off

Multiple Choice

Required by cells to create or maintain the structure, or enable the functioning, of the cell or organism

• Regulatory genes

• Inducible enzymes

• Structural genes

• Repressible enzymes

Multiple Choice

Control the expression of one or more genes.

• Regulatory genes

• Inducible enzymes

• Structural genes

• Repressible enzymes

Multiple Choice

Production can be turned off.

• Regulatory genes

• Inducible enzymes

• Structural genes

• Repressible enzymes

​Case Studies of Gene Regulation

• ​Lac Operon in Prokaryotes

  • ​a mechanism that ensures that the enzymes required for the metabolism of lactose are produced only in the presence of lactose. It has been observed in bacteria, such as E. coli

​Case Studies of Gene Regulation

• ​Regulation in Eukaryotes by enhancers and transcription factors

  • In eukaryotes, before mRNA can be transcribed by the enzyme RNA polymerase it first binds together with a small group of proteins called general transcription factors at a sequence of bases known as the promoter.

Open Ended

Make a summary of the Lac Operon .