Module 6

• What are the main topics covered in topic six of the OCR A module?

  • Cellular control
  • Gene mutations
  • Protein synthesis control
  • Gene expression control
  • Genetic control of body development
  • Inheritance
• What is a gene mutation?

  A gene mutation is a change in the base sequence of DNA.
• When do gene mutations typically occur?

  They occur randomly during DNA replication in the S phase of interphase.
• What increases the likelihood of mutations occurring?

  Exposure to mutagenic agents increases the likelihood of mutations.
• Name two types of gene mutations.

  Deletion and substitution.
• What happens during a substitution mutation?

  One nucleotide is swapped for a different base, potentially changing the amino acid coded.
• What is a silent mutation?

  A silent mutation is when a substitution does not change the amino acid due to the degenerate nature of the genetic code.
• What is a deletion mutation and its consequence?

  A deletion mutation removes a nucleotide, causing a frame shift that alters subsequent codons.
• How do transcription factors control protein synthesis?

  Transcription factors bind to DNA to initiate or inhibit transcription.
• Where do transcription factors move from and to?

  They move from the cytoplasm into the nucleus.
• What is the role of RNA polymerase in transcription?

  RNA polymerase binds to DNA to initiate the synthesis of mRNA.
• What happens if a transcription factor does not bind to DNA?

  The gene remains inactive because transcription cannot occur.
• What is an operon?

  An operon is a group of simultaneously controlled genes that are either all expressed or not.
• Which operon is commonly studied in E. coli?

  The Lac operon.
• What is the function of the Lac operon?

  The Lac operon is involved in lactose digestion when glucose is absent.
• What does the Lac L gene code for?

  The Lac L gene codes for a repressor protein that inhibits transcription when lactose is absent.
• How does lactose affect the repressor protein in the Lac operon?

  Lactose binds to the repressor protein, changing its shape and preventing it from binding to the operator.
• What role does cyclic AMP play in the Lac operon?

  Cyclic AMP increases the rate of transcription of the Lac operon by binding to the CRP.
• What is epigenetics?

  Epigenetics is the heritable change in gene function without changing the DNA base sequence.
• How can epigenetic changes be inherited?

  Epigenetic changes can be passed from cell to cell during replication.
• What is the effect of methylation on gene transcription?

  Increased methylation prevents transcription by tightly coiling DNA.
• What happens when acetyl groups bind to histone proteins?

  Acetyl groups cause looser packaging of DNA, allowing transcription to occur.
• What is alternative splicing?

  Alternative splicing allows for the removal of exons along with introns, producing different mRNA molecules from one gene.
• How does alternative splicing contribute to protein diversity?

  It allows a single gene to code for multiple proteins by producing different mRNA molecules.
• What modifications occur to mRNA after transcription?

  Introns are removed, and protective caps are added to the 5' and 3' ends.
• What is the role of Hox genes?

  Hox genes regulate the expression of other genes involved in body development.
• How are Hox genes organized in DNA?

  The order of Hox genes in DNA corresponds to the order of their effects on body development.
• What is the significance of symmetry in body development?

  Symmetry indicates the organization of body parts, which can be radial or bilateral.
• What is the role of mitosis in body development?

  Mitosis increases the number of cells, contributing to body growth.
• What is apoptosis?

  Apoptosis is programmed cell death that removes unwanted cells.
• How do tumor suppressor genes function?

  Tumor suppressor genes produce proteins that stop the cell cycle when no more cells are needed.
• What do proto-oncogenes do?

  Proto-oncogenes produce proteins that initiate the cell cycle when new cells are needed.
• How do external and internal stimuli affect the cell cycle?

  They can influence the regulation of mitosis and apoptosis.
• What are the key terms related to inheritance that students should know?

  • Monohybrid inheritance
  • Codominance
  • Multiple alleles
  • Sex linkage
  • Autosomal linkage
  • Epistasis
  • Dihybrid inheritance
• What is monohybrid inheritance?

  Monohybrid inheritance involves one gene with dominant and recessive alleles.
• How is codominance represented in genetic diagrams?

  Codominance is represented by using two different capital letters for the dominant alleles.
• What are multiple alleles?

  Multiple alleles refer to the presence of more than two alleles for a gene.
• How is sex linkage represented in genetic diagrams?

  Sex linkage is represented by indicating whether the allele is on the X or Y chromosome.
• What is the probability of having a child with cystic fibrosis if both parents are carriers?

  The probability is 25% for having a child with cystic fibrosis.
• What is the probability of having a girl with cystic fibrosis if both parents are carriers?

  The probability is 12.5% for having a girl with cystic fibrosis.