genetic development

• 1. Methylation is the addition of a methyl group. decreases gene expression.
  2. Acetylation is the addition of a acetyl group. increases gene expression.
  3. lac operon is activated when no glucose is available.
  4. RNA splicing is when introns are cut out of mRNA chain leaving just exons.
  5. Regulatory genes code for proteins that inhibit or increase expression of structural genes.
  6. Structural genes code for proteins that are not involved in the regulation of gene expression.
  7. Proteins can be modified after translation by adding carbohydrates, lipids, by folding , by adding a phosphate group
• • Cell differentiation = when cells change their shape, size and organelle distribution to become specialised to a particular function.
  • Morphogenesis = How anatomy develops during embryonic development.
  • Fertilised eggs form a zygote then blastocyst then embryo then foetus
• During early embryonic development many animal embryos look extremely similar.

  Even once organisms are heavily differentiated and phylogenetically distant, similar features are still present.
• • A homeobox gene is a regulatory gene.
  • They code for a protein that binds to DNA and switches genes on or off during early embryonic development.
  • These genes are highly conserved across nature because there is no selection pressure to change such key developmental genes. They are fundamental to the development of a normal body structure.
• Hox genes are a group of homeobox genes that control body development – gross anatomy.

  The order of Hox genes on the chromosomes control each body segment e.g. Hox genes in the thorax control thoracic development. Hox genes in the head control mouth development
• Segments of the embryo are called somites.

  The segments are directed by Hox genes to develop in a particular way depending on where they are in the sequence.

  E.g. Somites at the bottom will form tail components or hind limb structures.
• when lactose is present in a medium, it is known as the inducer. This polysaccharide binds to its specific site on the repressor protein resulting in a change in the shape of this protein’s other binding site. This conformational change means that the repressor protein is unable to bind to the terminator region and moves away, leaving the promoter region unblocked. DNA polymerase binds to the promoter region and initiates the transcription of mRNA for the structural genes Y and Z. Translation follows, leading to the synthesis of lactose permease and beta galactosidase.
• Mitosis = Asexual cell division. Creates more cells.

  Apoptosis = Programmed cell death. Reduces the number of cells. Is different from cell death from trauma or disease.