DNA, Genes and Chromosomes

• Inheritance - the transmission of genetic information from generation to generation
• DNA molecules are in the structure of a double helix

  • two sides that twist together
  • made up of a backbone
  • each backbone connects to a based (A,T,C,G)
• DNA molecules are in the structure of a double helix

  • two sides that twist together
  • made up of a backbone
  • each backbone connects to a based (A,T,C,G)
• Chromosomes are located in the nucleus of cells

  • thread-like structures of DNA, carrying genetic information in the form of genes
• Gene - a short length of DNA found on a chromosome that codes for a specific protein

  • could be a structural protein such as collagen found in skin cells, an enzyme or a hormone
• Genes controls our characteristics as they code for proteins that play important roles in what our cells do
• • Genetic information in the cell

  A) double

  B) helix

  C) dna

  D) chromosome

  E) dna

  F) proteins

  G) nucleus

  H) chromosomes

  
• Alleles are different versions of a particular gene

  • the ABO gene for blood group type has three alleles: IA, IB and IO
• Alleles give all organisms their characteristics
• Members of the same family share the same characteristics because they inherit the DNA from the two parents
• DNA and genes are unique

  • except for twins
• Nucleus contains chromosomes made up of a string of genes
• Different genes control the development of different characteristics by issuing instructions to the cell to make a protein

  • Genes have slightly different codes → different proteins are made → different characteristics
• Order of organization (smallest to biggest):

  • Gene
  • Chromosome
  • Nucleus
  • Cell
• Genes produce a protein
• Allele - different forms of a gene
• What is the order of size of structures: gene, DNA strand, chromosomes, nucleus

  gene →  DNA strand →  chromosomes →  nucleus
• What type of cells are produced by meiosis?

  Gametes because meiosis creates genetically different cells with a haploid number of chromosomes
• Define allele

  Allele is a version of a gene
• Why is it important that only some genes of a certain type are expressed?

  Organisms have different structures and specialised cells and they each have their different functions and roles. Specific proteins are required for different specialised cells and genes codes for different proteins so some genes are not required.