DNA

• Making copies of DNA

  REPLICATION
• James Watson and Francis Crick worked out that DNA is double helix like a twisted staircase


  1953
• When DNA replicates, two identical copies of DNA molecules are produced, which are exactly the same as the original
• Three types of RNA that help build proteins

  • Messenger RNA (mRNA)
  • Ribosomal RNA (rRNA)
  • Transfer RNA (tRNA)
• Transcription


  The order of nucleotides in DNA determines the order of nucleotides in messenger RNA
• Translation


  The process of converting the information in mRNA into a sequence of amino acids that make a protein
• Three phases during transcription

  1. Initiation: The ribosome assembles around the target mRNA. The first tRNA is attached at the start codon

  2. Elongation: The tRNA transfers an amino acid to the tRNA corresponding to the next codon. The ribosome then moves (translocates) to the next mRNA codon to continue the process, creating an amino acid chain

  3. Termination: When a stop codon is reached, the ribosome releases the polypeptide
• The central dogma of molecular biology
• Each nucleotide has three parts: a sugar molecule (deoxyribose), a phosphate group, and one of four nitrogenous bases (adenine, thymine, cytosine, or guanine).
• The structure of DNA consists of two strands twisted together into a double helix, with nucleotides forming rungs on the ladder-like structure.
• DNA is the genetic material that contains instructions to make proteins.
• DNA contains two strands held together by hydrogen bonds between complementary base pairs.
• DNA replication occurs through semiconservative replication, where each new strand contains one old strand and one newly synthesized strand.
• Protein synthesis involves translation, where the genetic code stored in DNA is used to create specific sequences of amino acids.
• Transcription is the process by which RNA copies are made from DNA templates.
• In transcription, DNA serves as a template for making RNA, while in translation, RNA serves as a template for making proteins.
• Cytosine always binds to Guanine through three hydrogen bonds.
• Ribonucleic acid (RNA) is a single-stranded molecule made up of ribonucleotides linked by phosphodiester bonds.
• There are different types of RNA, including messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA).
• Protein synthesis involves transcription, where mRNA is produced from DNA, and translation, where amino acids are assembled into polypeptides based on the sequence of codons in mRNA.
• Transcription is the process of copying DNA into mRNA, while translation is the process of using mRNA to build proteins.
• Translation is the process by which ribosomes read mRNA molecules and assemble amino acids according to their sequence.
• The central dogma states that information flows from DNA to mRNA to protein.
• Types of cells where mutations can occur

  • Reproductive cells (sex cells)
  • Body cells (somatic cells)
• Germline mutations


  Mutations that affect the reproductive cells of an organism by changing the sequence of nucleotides within a gene in a sperm or an egg cell
• Somatic mutations


  Mutations that can occur in any of the cells of the body except the germ cells and therefore are not passed on to offspring
• Types of mutations that can occur in gamete cells

  • Gene mutation
  • Chromosomal mutation
• Gene mutation


  A permanent change in the DNA sequence that makes up a gene
• Chromosomal mutation


  Occurs at the chromosome level resulting in gene deletion, duplication or rearrangement that may occur during cell cycle and meiosis. It maybe caused by parts of chromosomes breaking off or rejoining incorrectly.
• When an acquired mutation occurs in an egg or sperm cell


  It can be passed down to the individual's offspring
• Once an acquired mutation is passed down, it is a hereditary mutation
• Types of gene mutations

  • Point mutation
  • Silent mutation
  • Nonsense mutation
• Point mutation


  A change in a genetic sequence that occur at a specific point along the DNA strand. It also occurs in a genome when a single base pair is added, deleted or changed.
• Silent mutation


  Base substitutions that result in no change of the amino acid
• Nonsense mutation


  Occurs when a premature nonsense or stop codon is introduced in the DNA sequence. They do not code for an amino acid instead signal the end of protein synthesis.
• dna mutations