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Gene Expression

Edexcel A-level BiologyTopic 7 of 1639 lessons

Revision notes for Gene Expression in Edexcel Biology B (9BI0). Every lesson in BrainCake comes with R.E.C.I.P.E. recall steps, a quick check and spaced reviews.

  1. Gene ExpressionGene expression is the process by which the information in a gene is used to make a functional product, usually a protein.
  2. Gene ProbesA gene probe is a short, single-stranded piece of DNA or RNA with a base sequence complementary to a particular gene or allele.
  3. Control of Gene ExpressionCells control which genes are expressed and how much protein is made.
  4. Transcription FactorsTranscription factors are proteins that control whether a gene is transcribed.
  5. RNA SplicingIn eukaryotes, genes contain exons (coding sequences) separated by introns (non-coding sequences).
  6. EpigeneticsEpigenetics is the study of changes in gene expression that do not involve a change in the base sequence of DNA.
  7. DNA MethylationDNA methylation is the addition of a methyl group (-CH3) to a cytosine base in DNA.
  8. DNA DemethylationDNA demethylation is the removal of methyl groups from cytosine bases in DNA.
  9. Euchromatin and HeterochromatinIn eukaryotic nuclei, DNA is wound around proteins called histones.
  10. Histone AcetylationHistone acetylation is the addition of acetyl groups (-COCH3) to histone proteins.
  11. Histone MethylationHistone methylation is the addition of methyl groups (-CH3) to histone proteins, usually to lysine (and sometimes arginine) amino acids in the…
  12. non-Coding RNAOnly a small proportion of the genome codes for proteins, but much of the rest is transcribed into RNA.
  13. siRNASmall interfering RNA (siRNA) is short, double-stranded RNA, about 21 to 23 nucleotides long, that silences a specific gene by causing its mRNA to…
  14. Cell DifferentiationCell differentiation is the process by which an unspecialised cell becomes specialised to carry out a particular function.
  15. Early Stages of DevelopmentA new organism begins as a single cell, the zygote, formed when an egg is fertilised by a sperm.
  16. Stem CellsStem cells are undifferentiated cells that can: • divide by mitosis again and again to produce more stem cells (self-renewal) • differentiate into…
  17. Embryonic Stem CellsEmbryonic stem cells are stem cells taken from an early embryo.
  18. Umbilical Cord Stem CellsThe umbilical cord connects a baby to the placenta during pregnancy.
  19. Adult Stem CellsAdult stem cells, also called somatic stem cells, are undifferentiated cells found among the specialised cells of tissues and organs in children and…
  20. Determination of Cell TypeDetermination is the process by which a cell becomes committed to developing into a particular type of cell.
  21. Evidence for Cell DeterminationSeveral classic experiments show that cells become determined at a particular stage of development, and that this depends on gene expression rather…
  22. Development of an OrganismEvery cell in a multicellular organism comes from a single fertilised egg, the zygote.
  23. Epigenetic Control of DevelopmentEpigenetics is the study of heritable changes in gene function that happen without a change in the base sequence of DNA.
  24. Epigenetic Control of Gene ExpressionEpigenetic marks control whether RNA polymerase and transcription factors can reach a gene.
  25. Stem Cell TherapyStem cells are undifferentiated cells that can divide repeatedly and differentiate into specialised cells.
  26. Therapeutic CloningTherapeutic cloning produces embryonic stem cells that are genetically matched to a patient.
  27. Gene EditingGene editing changes the base sequence of DNA at a precise, chosen place in the genome.
  28. Potential Benefits of Stem Cell TherapyStem cell therapy has the potential to transform medicine because stem cells can divide indefinitely in culture and differentiate into specialised…
  29. Pitfalls of Stem Cell TherapyStem cell therapy also has serious risks and practical problems that must be solved before most treatments become routine.
  30. Induced Pluripotent Stem CellsInduced pluripotent stem cells (iPS cells) are specialised adult cells that have been reprogrammed to behave like embryonic stem cells.
  31. Diseases that Could Be TreatedStem cell therapy is most promising for diseases caused by the loss or damage of a particular cell type that the body cannot replace.
  32. Type I DiabetesType 1 diabetes is an autoimmune disease.
  33. Damaged NervesNeurones in the brain and spinal cord (the central nervous system) have very limited ability to regenerate after injury or disease.
  34. Organs for TransplantsThere are far fewer donor organs available than there are patients who need transplants, and many people die while waiting.
  35. Stem Cell SuccessAlthough many stem cell treatments are still experimental, some are established and successful.
  36. Ethical QuestionsStem cell research, especially using embryos, raises ethical questions on which people hold strongly different views.
  37. Using Embryonic Stem CellsEmbryonic stem cells are taken from the inner cell mass of a blastocyst, an early embryo about 5 days after fertilisation.
  38. Advantages of Therapeutic CloningTherapeutic cloning (somatic cell nuclear transfer) avoids one major problem of embryonic stem cells from IVF embryos: because the nucleus comes…
  39. Advantages of iPS CellsInduced pluripotent stem cells (iPS cells) offer a way round many of the ethical problems of embryonic stem cells.

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