ifhy bio

SECTION I: HISTORY OF DNA

  • frederick griffith: bacterial transformation

  • alfred hershey and martha chase: dna carries genetic info in bacteriophages

  • james watson and francis crick: discovering 3d structure of dna

  • erwin chargaff: chargaff’s rules (base pair regularity)

  • rosalind franklin: x-ray diffraction images

SECTION II: THE STRUCTURE OF DNA

  • dna: genetic material that carries info about an organism passed from parent to offspring in cells

  • 3 components that make up a nucleotide: phosphate group, deoxyribose sugar, nitrogenous base

  • what type of bond makes up sugar phosphate backbone of dna: phosphodiester bonds

  • bond that connects nitrogenous bases: hydrogen bonds

  • 2 between adenine and thymine

  • 3 between cytosine and guanine

  • why are dna strands considered antiparallel: the strands replicate in opposite directions

  • two main groups that base pairs can be divided into: purines and pyrimidines

  • purines: double carbon nitrogen rings (adenine and guanine)

  • pyrimidines: single carbon nitrogen rings (cytosine and guanine)

SECTION III: DNA REPLICATION

  • DNA replication: the process of producing two identical copies of DNA from one original DNA molecule

  • where does DNA replication begin: the origin of replication

  • difference between leading and lagging

  • leading: replicates toward replication fork, synthesized continuously, in mandatory 5’ -> 3’

  • lagging: replicates away from replication fork, cannot be synthesized continuously, needs multiple starting points which results in okazaki fragments

  • major proteins/enzynes

  • helicase: enzyme that opens double helix by breaking the hydrogen bonds that hold the two strands together

  • DNA polymerase: links nucleotide subunits to form a new DNA strand that is complementary to the DNA template

  • DNA ligase: links okazaki fragments by joining the 3’ end of the new DNA fragment to the 5’ end of the adjoining DNA

  • exonuclease: enzyme that removes nucleotides from the end of a DNA strand; proofreading enzyme that checks for errors during replication; removes primers from DNA okazaki fragments

SECTION IV: TRANSCRIPTION

  • transcription: the process through which a DNA sequence is copied into a complementary mRNA molecule in the nucleus

  • product of transcription: RNA molecule made of nucleotides complementary to the DNA template strand

SECTION V: TRANSLATION

  • translation: the decoding of an mRNA message into a protein in the cytoplasm, on a ribosome

  • 1. mRNA leaves nucleus and enters cytoplasm, where it attaches to ribosome (which makes proteins)

  • 2. START codon tells the cell where to begin translation

  • 3. ribosome gets together w/ the mRNA and the first tRNA so translation can begin

  • 4. ribosome moves along mRNA strand treading the codons and attracting tRNA molecules with the complementary anticodon

  • 5. tRNA molecule carries the amino acid being coded for and attaches it to the newly formed polypeptide chain

  • 6. once tRNA molecule has dropped off its amino acid, it releases itself from the mRNA and leaves the ribosome to pick up another amino acid - the polypeptide chain of amino acids is a protein

  • 7. process continues until the ribosome reaches a STOP message, everything is then released from the ribosome

  • function of tRNA: acts as a link between mRNA and the amino acid. sequence being created

  • codons are found on mRNA, anticodons are found on tRNA

  • hydrogen bonds are formed between amino acids during translation

SECTION VI: DNA MUTATIONS

  • mutagens: chemical or physical agents that can cause mutations, or changes in the DNA sequence of an organism (chemical: dyes or chemicals, physical: exposure to radiation [x-rays, gamma rays, UV rays])

  • types of mutations

  • insertion: one to several base pairs are inserted into a DNA molecule

  • deletion: one to several base pairs are deleted from a DNA molecule

  • inversion: chromosome segment is reversed from end to end

  • nonsense: codon is substituted to a stop

  • missense: codon is substituted for another to code for a different amino acid

  • substitution: one codon is replaced by another

  • duplication: segment of dna sequence is duplicated, leading to extra copies of a gene or region of chromosome

  • transposons: DNA segments that move spontaneously from one location to another in the same DNA molecule or to another one

  • point mutation: changes in DNA that occur at a single point/nucleotide in a DNA sequence

  • silent mutation: does not cause a change in the amino acid sequence because the new codon codes for the same amino acids as the original