Science DNA

• Nucleic acid (DNA and RNA)

  A large molecule composed of carbon, oxygen, nitrogen, and phosphorus

  
• Nucleotide


  The building blocks of nucleic acid, consisting of a phosphate group, a sugar, and a nitrogen base

  
• DNA


  • Two strands of nucleotides joined together to form a twisted ladder called a double helix
  • Cells of the human body contain 23 pairs of chromosomes made up of DNA
  • DNA is located inside the nucleus of the cell and is highly coiled molecules that contains genes
  • Genes determine all the features found in living cells such as the structure of the hair, complexion, bone structure, color of eyes

  
• Polymer


  A very large chain of repeating units, which are large, carbon-based molecules formed by monomers
• DNA


  • Consists of an equal amount of four nucleotides that are important to the operation and cell reproduction
  • Each nucleotide contains a phosphorus with four oxygen (phosphate group), a five-carbon sugar (deoxyribose), and a nitrogen-containing base (either a single-ringed pyrimidine or a double-ringed purine)

  
• Chargaff's Rule of DNA

  • Adenine must pair with thymine (A-T)
  • Guanine must pair with cytosine (G-C)
  • The bases form weak hydrogen bonds

  
• Genetic code


  The set of rules used by living cells to translate information encoded within genetic material (DNA or mRNA sequences of nucleotide triplets, or codons) into proteins
• Characteristics of the Genetic Code

  • The genetic code is universal (all known living organisms use the same genetic code)
  • The genetic code is unambiguous (each codon codes for just one amino acid or start/stop)
  • The genetic code is redundant (most amino acids are encoded by more than one codon)
• DNA Replication


  1. DNA replication takes place in the cytoplasm of prokaryotes and in the nucleus of eukaryotes

  2. The enzymes start to unzip the double helix as the nucleotide base pairs separate

  3. Free nucleotides pair with the base exposed as the template strand continuously unzip

  4. An enzyme complex-DNA polymerase attach the nucleotide together to form new strand similar to each template

  5. A sub-unit of the DNA polymerase proofreads the new DNA and the DNA ligase seals up the fragments into one long strand

  6. Two similar double-stranded molecules of DNA result from replication

  
• Protein


  • Different types of proteins exist in every living organisms
  • The human body contains at least 10,000 different kinds of proteins
  • Proteins are large, complex molecules composed mainly of oxygen, hydrogen, carbon, and nitrogen
  • Proteins are an essential part of the structure of cells and act as enzymes or catalysts for chemical reactions in cells
• Amino acids


  • The building blocks of proteins, which are made up of long chains of chemical units
  • There are 20 different amino acids
  • The body can synthesize 11 non-essential amino acids through metabolic process from simple organic molecules, and the 9 essential amino acids must be obtained from dietary food
• Non-essential Amino Acids


  • Glycine
  • Arginine
  • Cysteine
  • Proline
  • Tyrosine
  • Alanine
  • Glutamic acid
  • Glutamine
  • Serine
  • Asparagine
  • Aspartic acid
• Essential Amino Acids


  • Histidine
  • Isoleucine
  • Leucine
  • Lysine
  • Methionine
  • Phenylalanine
  • Threonine
  • Tryptophan
  • Valine
• Importance of Proteins in the Body

  • Protein hormones regulate many physiological processes, like insulin, that affects glucose transport into cells
  • Proteins in the blood help as blood clotting factor and transport molecule (hemoglobin transports oxygen in the blood)
  • Proteins act as ion channels, carrier, and receptor molecules in the cell membrane
• Messenger RNA (mRNA)


  A type of RNA molecule that travels from the nucleus to the ribosomes in the cytoplasm, where the copied information from the DNA is used for a protein product
• Ribosomal RNA (rRNA)


  The RNA component of the ribosome and a cell's protein factory in all living cells, providing a mechanism for decoding mRNA into amino acid and interacting with tRNA
• Transfer RNA (tRNA)


  An adaptor molecule composed of RNA, typically 73 to 93 nucleotides in length, that brings amino acids from the cytoplasm to a ribosome to help make the growing protein
• Transcription


  1. The genetic information within the DNA is copied into the mRNA through the process of transcription

  2. The DNA strand will be exposed once the DNA molecules uncoils

  3. The RNA polymerase is responsible for the alignment and binding together of the ribonucleotides that will create the single strand of RNA molecules

  4. The mRNA molecule attaches to the exposed bases of the DNA strand

  
• Translation


  1. Each tRNA with its attached specific amino acid moves to the mRNA-ribosome complex

  2. The mRNA molecule attaches to the ribosome, which forms the mRNA-ribosome complex

  3. An amino acid is then attached to a specific transfer RNA (tRNA)

  4. The ribosome changes its position by three nucleotides, the tRNA without the amino acid is detached from the ribosome

  5. The ribosome now shifts to the next codon, ready to bind another tRNA with its specific amino acid

  6. The mRNA codon recognizes which tRNA is next, specifying which amino acid will be next in the polypeptide chain

  7. The process is repeated as the ribosome goes along the mRNA chain
• Guanine-Cytosine pairing


  Guanine must pair with cytosine (G-C)
• Adenine-Uracil pairing


  Adenine must pair with uracil (A-U)
• Protein Synthesis


  1. DNA unravels or unzips in the nucleus, exposing the code

  2. mRNA nucleotides come in

  3. Transcription (copying genetic code from DNA) by the mRNA

  4. mRNA exits nucleus, goes to ribosome

  5. Translation (gives message to ribosome), mRNA attaches to ribosome and first codon is read

  6. tRNA brings in specific amino acids (anticodons) from cytoplasm

  7. Protein synthesis begins in the ribosome and a second tRNA brings new amino acid

  8. Polypeptide chain is produced, a protein made out of a chain of amino acids

  9. Termination, the ribosome reads the stop codon (UAA, UAG, UGA) in the mRNA