Control of Gene Expression

• What are mutations?


  Changes in the sequence of nucleotides in DNA molecules
• What are the types of mutations?


  • Insertion/deletion mutations
  • Duplication
  • Inversion
  • Translocation
• What happens during insertion/deletion mutations?


  One or more nucleotide pairs are inserted or deleted, causing a frameshift
• What is a frameshift mutation?


  A mutation that alters the sequence of nucleotides after the mutation point
• What occurs during a duplication mutation?


  One or more bases are repeated, producing a frameshift
• What is an inversion mutation?


  A group of bases is separated and rejoined in reverse order
• How does translocation affect DNA?


  A group of bases is moved from one chromosome to another
• What can cause mutations?


  Spontaneous errors during DNA replication and mutagenic agents
• What are the types of chemical mutagens?


  • Alcohol
  • Benzene
  • Asbestos
  • Tar in tobacco
• What types of radiation can cause mutations?

  Ionising radiation, including alpha, beta, UV, and X-ray
• What are neutral mutations?


  Mutations that cause no change to the organism
• Give an example of a beneficial mutation.


  The development of trichromatic vision in humans
• What is a harmful mutation?


  A mutation that negatively affects the organism, such as in cystic fibrosis
• What are stem cells?


  Undifferentiated cells that can divide to give rise to other cell types
• What are the types of stem cells?

  • Totipotent: can form any type of cell, including embryonic cells
  • Pluripotent: can form any cell type except extra embryonic cells
  • Multipotent: can differentiate into limited cell types
  • Unipotent: can only differentiate into one type of cell
• What are totipotent stem cells?


  Stem cells that can differentiate into any type of cell and extra embryonic cells
• Where are totipotent stem cells found?


  In the early embryo, specifically in the blastomere stage
• What happens when totipotent stem cells become specialized?


  They differentiate to form tissues that make up the fetus
• What causes the specialization of stem cells?


  A change in gene expression where some genes are switched on and others off
• What is the role of oestrogen in transcription regulation?


  It alters transcription by binding to transcription factors
• Describe the process of oestrogen's action in transcription regulation.


  1. Oestrogen diffuses across the cell membrane
  2. Binds to a receptor on a transcription factor
  3. Alters the shape of the DNA binding site
  4. Enters the nucleus and binds to DNA
  5. Stimulates transcription of the gene
• What is small interfering RNA (siRNA)?


  RNA used for short-term switching off of genes
• How does siRNA work?


  It binds to complementary mRNA, leading to its breakdown
• What is epigenetics?


  • Heritable changes in gene function without changes to the DNA sequence
  • Environmental factors can influence gene function
• What is DNA methylation?


  A process where methyl groups are added to DNA, suppressing gene transcription
• How does DNA methylation affect gene expression?


  It alters gene expression as cells divide and specialize
• What is the effect of decreased acetylation of histones?


  It increases the binding of histones to DNA, preventing transcription
• How can cancer arise from mutations?


  Uncontrolled cell division leads to tumor formation
• What are the two types of tumors?

  • Benign: grow slowly, do not spread, cause light damage
  • Malignant: grow rapidly, can spread, disrupt processes
• What are proto-oncogenes?


  Genes that stimulate cell division and can cause cancer if mutated
• What are oncogenes?


  Mutated proto-oncogenes that cause uncontrolled cell division
• What is the role of tumor suppressor genes?


  They control cell division and can trigger apoptosis when damage is detected
• What is hyper-methylation?


  Increased methylation that can control tumor suppressor genes and oncogenes
• How can increased oestrogen concentrations relate to breast cancer?


  Elevated oestrogen can activate genes promoting cell division, leading to tumors
• What are the applications of genome projects?


  • Identifying potential antigens for vaccines
  • Understanding evolutionary relationships
  • Developing personalized medicine
  • Screening for genetic disorders
• What is the Human Genome Project?


  An international project that determined the sequence of bases in the human genome
• What are the ethical concerns regarding the Human Genome Project?


  Discrimination and misuse of genetic information
• What is recombinant DNA technology?


  • Manipulating DNA in various ways
  • Involves processes like reverse transcriptase and restriction endonucleases
• What is the function of reverse transcriptase?


  It catalyzes the formation of DNA from RNA
• What are restriction endonucleases?


  Enzymes that cut DNA at specific sequences