DNA, Central Dogma, & Biomolecules

• Elements in nucleic acids

  • C
  • H
  • O
  • N
  • P
• Nucleic acid


  The genetic material of all organisms, composed of the elements C, H, O, N, P
• Nucleotide


  The repeating unit of nucleic acids, consisting of a 5-carbon sugar, nitrogen base, and phosphate group
• Nitrogen bases in nucleic acids

  • A-adenine
  • T-thymine
  • C-cytosine
  • G-guanine
  • U-uracil
• RNA


  • The genetic material of retroviruses
  • Functions in gene expression
  • Single stranded
  • Has 4 bases: A, G, C, U
  • Sugar: ribose
• DNA


  • The genetic material of most organisms
  • In the form of double strand
  • Has 4 bases: A, G, C, T
  • Sugar: deoxyribose
• The Central Dogma


  1. Replication

  2. Transcription

  3. Translation
• DNA Replication


  1. DNA molecule builds an exact copy of itself

  2. Occurs in the nucleus in eukaryotes, and in the cytoplasm in prokaryotes

  3. The two complementary DNA strands are separated by the enzyme helicase forming the replication fork

  4. Each strand serves as the template for production of its complement

  5. DNA polymerases create complementary strands

  6. Replication is from 5' to 3' direction, leading and lagging strands
• Transcription


  1. Making RNA from a DNA template, the first step of gene expression

  2. Occurs in the nucleus

  3. RNA Polymerase and transcription factors bind to promoter DNA

  4. A transcription bubble is formed as the two DNA strands separate, serving as the template for RNA

  5. RNA Polymerase forms an RNA strand complementary to the DNA strand

  6. Transcription proceeds from 5'-3' direction and stops at termination signals
• Translation


  1. Synthesis of protein from an mRNA template

  2. Occurs in the cytoplasm

  3. mRNA from the nucleus is transported to the cytoplasm

  4. Three nucleic acids correspond to a single amino acid (codon)

  5. Start codon (AUG) signals the starting point and codes for methionine

  6. Ribosomes translate the RNA strand into interconnected amino acids

  7. Translation stops at stop codons (UAA, UAG, UGA)
• The information that is eventually translated into a protein is held in the nitrogenous bases of the DNA molecule
• Each individual strand of DNA during replication is made up of nitrogenous bases attached to a sugar-phosphate backbone
• In a double-stranded DNA molecule, the amount of adenine is always equal to the amount of thymine
• If a section of DNA has 13% cytosine, then there is 74% guanine
• Pathway for producing microtubule proteins

  DNA → mRNA → polypeptide → protein
• DNA replication in skin cells produces identical daughter skin cells
• The complementary strand to 3' ATTCGGGATATF 5' is 5' TAAGCCCTATAA 3'
• During transcription, an mRNA molecule is created from the DNA molecule
• The largest type of RNA produced is ribosomal RNA (rRNA)
• Messenger RNA (mRNA) transmits the information from the DNA to the ribosomes
• The three-base sequence of DNA codes for one amino acid
• If an mRNA contains the codons GCU UAU, the corresponding tRNA should have the anticodons CGA AUA
• Point mutations


  Mutations that involve addition, deletion, or substitution of a few bases
• The sequence that signals the end of translation is called the stop codon
• Induced mutations


  Mutations that involve addition, deletion, or substitution of a few bases
• Point mutations


  One or few bases is changed, deleted or added to the DNA
• Shift mutations


  Mutations that involve addition, deletion, or substitution of a few bases
• Nonsense mutations


  Mutations that involve addition, deletion, or substitution of a few bases
• Genetics


  The science that deals with the study of inherited characteristics and variation among organisms
• Gene


  Segment of DNA that contains the information to make one protein
• Chromosome


  Contains the hereditary material (DNA or RNA) packaged with histone proteins
• Alleles


  Different variants of a gene resulting in a contrasting effect on characteristics
• Dominant


  Masks the effect of the recessive allele, represented by capital letter
• Recessive


  Allele being masked by the dominant allele, represented by small letter
• Genotype


  The pair of alleles for a particular trait in one individual
• Homozygous dominant


  When all alleles present are both dominant
• Homozygous recessive


  When all alleles present are both recessive
• Heterozygous


  When both dominant and recessive alleles are present
• Phenotype


  Observable trait of an individual determined by the genotype
• Carrier


  A person who is heterozygous at the gene locus of a disorder but shows no signs of the disorder