GEN BIO 2

• DNA (DEOXYRIBONUCLEIC ACID)


  A nucleic acid that consists of two long chains of nucleotides twisted together into a double helix and joined by hydrogen bonds, it carries the cell's genetic information and hereditary characteristics via its nucleotides
• DNA

  The blueprint of life
• Components of the DNA molecule


  • Phosphate group
  • The sugar deoxyribose
  • The bases adenine, thymine, cytosine, guanine (A,T,C,G)
• Components of a nucleotide

  • One phosphate group
  • One sugar molecule
  • One of the four bases
• Nitrogenous base pairing in DNA

  A always pairs with T, and G with C
• RNA


  Structure differs from DNA in three ways: 1) RNA is single-stranded, 2) the sugar in RNA is ribose, 3) RNA contains uracil (U) instead of thymine
• Major types of RNA

  • Messenger RNA (mRNA)
  • Ribosal RNA (rRNA)
  • Transfer RNA (tRNA)
• Chromosome


  The microscopic thread-like part of the cell that carries hereditary information in the form of genes
• Humans have 23 pairs of chromosomes
• Chromosomes carry hereditary information and inherited traits</b>
• DNA is responsible for long-term storage of the genetic code and resides in the nucleus of eukaryotic cells
• RNA is responsible for transporting the genetic information found in DNA to other sites in the cell where it can be used to make proteins, and is found in the cytoplasm of a cell
• Each nucleotide contains a pentose sugar called deoxyribose, a phosphate group, and one of the four nitrogenous bases
• The backbone of DNA supports four bases: Thymine, Adenine, Guanine, and Cytosine, which pair as T-A and C-G
• There are no mismatched DNA base pairs, as A only pairs with T and C only pairs with G
• There are no missing DNA base pairs, the pairing is always A-T and C-G
• Central Dogma of Molecular Biology


  A theory stating that genetic information flows only in one direction, from DNA, to RNA, to protein
• The Central Dogma of Molecular Biology was proposed by the National Human Genome Research Institute (NHGRI)
• DNA


  Deoxyribonucleic acid
• RNA


  Ribonucleic acid
• Three main types of RNA

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


  Contains the information for the encoding of proteins
• Transfer RNA (tRNA)


  Carries amino acids needed to make protein
• Ribosomal RNA (rRNA)


  Found in ribosomes, aids in manufacturing proteins
• Gene expression


  The process by which the instructions present in our DNA are converted into a functional product, such as a protein
• Three main processes involved in the Central Dogma

  • Replication
  • Transcription
  • Translation
• Replication


  Happens when DNA makes a copy of itself with the help of several enzymes
• Chargaff's Rule


  States that the amount of guanine nearly equals the amount of cytosine and adenine nearly equals the amount of thymine
• Chargaff's Rule


  • Erwin Chargaff was the first to accurately measure nucleotide amounts in DNA
• Stages in DNA Replication

  1. Helicase unzips the double helix structure of the DNA molecule

  2. Replication fork is created, a Y-shaped structure

  3. Leading strand is oriented 3' to 5', lagging strand is oriented 5' to 3'

  4. Nucleotides are added

  5. Exonuclease trips away the primers
• Continuous Replication in the Leading Strand


  1. Primase produces a short piece of RNA that binds to the end of the leading strand

  2. DNA polymerase binds to the leading strand and adds new complementary nucleotide bases
• Discontinuous Replication in the Lagging Strand


  1. Primase produces numerous RNA primers that bind at various points along the lagging strand

  2. Okazaki fragments are added to the lagging strand

  3. Exonuclease strips away the primers

  4. DNA ligase seals up the sequence of DNA into two continuous double strands
• The result of DNA replication is two DNA molecules consisting of one new and one old chain of nucleotides (semiconservative)
• The leading strand is oriented in the 3' to 5' direction, towards the replication fork
• The lagging strand is oriented in the 5' to 3' direction, away from the replication fork
• Central Dogma


  The fundamental molecular biological process by which genetic information flows from DNA to RNA to proteins
• Three (3) main processes involved in central dogma

  • Replication
  • Transcription
  • Translation
• Transcription

  1. DNA -> RNA (mRNA)

  2. Occurs in the nucleus

  3. A copy of mRNA is made that is complementary to a strand of DNA
• Transcription - Initiation

  RNA polymerase attaches to and moves along the DNA molecule until it recognizes a PROMOTER sequence
• Transcription - Elongation

  1. Template strand (3' to 5') provides a template for the new mRNA molecule

  2. Coding strand (5' to 3') has a base sequence that is identical to the synthesized mRNA, except for the replacement of Thymine bases with Uracil