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DNA and RNA Chapter 12 BIO Cheat Sheet by

Griffith and Transf­orm­ation

- Fredrick Griffith (British scientist)
- wanted to learn how bacteria makes you sick
- isolated two different strains (types) pnumenia
- diseas­e-c­ausing strain -> smoothing colonies on culture plates -> mice got pneumonia -> dies
- harmless strain -> colonies with rough edges -> lived
- but smooth + rough = pnumonia
- transf­orm­ation: one strain of bacteria changed perman­ently to another

Avery & DNA

- Oswald Avery (canadian biologist)
- avery & other scientists discovered that nucleic acid DNA stores & transmits the gentic nfo from one generation to the next

Hershe­y-Chase Experiment

- Alfred Hershey & Martha Chase (American scient­ists)
- bacter­iop­hage: one kind of virus that infects bacteria
- concluded that the genetic material of the bacter­iophage was DNA not protein

Components & Structure of DNA

- DNA is a lomg molecule made up of units called nucleo­tides
- nucleo­tides: 5-carbon sugar called deoxyr­ibose, phosphate group, and a nitrog­enous base
- 4 nitrog­enous bases: adenine, guanine, cytosine, thymine
- Watson & Crick's model of DNA was a double helix where two strands were wound around each other
- base pairing: for every adenine in a double stranded DNA molecule, there had to be one thymine molecule & for every cytosine molecule, there had to be one guanine molecule
- base pairing explained why Chargaff's rules (% of G and C was equal & A and T were equal)

DNA and Chromo­somes

- prokar­yotic cells lack nuclei
- eukaryotic DNA is located in the cell nucleus in the form of a number of chromo­somes
- humans have 46 chromo­somes
- eukaryotic chromo­somes carry DNA & protein in chromatin
- chromatin has DNA that is coiled around proteins called histones
- nucleo­somes: fold DNA into tiny space of cell nucleus

DNA Replic­ation

- strands of base pairing are comple­mentary
-before a cell divides, it duplicates its DNA in a copying process called replic­ation
- replic­ation -> DNA molecules separate into 2 strands -> produce 2 new comple­mentary strands thru base pairing -> each strand of double helix is a model for new strand
- DNA polymerase is a key enzyme in replic­ation: joins individual nucleo­tides to produce DNA molecule

Structure of RNA

double stranded
single stranded

Types of RNA

- RNA molecules -> protein synthesis (assembly of amino acids)
- messenger RNA, ribosomal RNA, transfer RNA
- mRNA: carry copies of instru­ctions for assembling amino acids into proteins
- rRNA: where proteins are assembled
- tRNA: transfers amino acid to ribosome by its coded messages


- transc­rip­tion: process where RNA molecules are produced by copying part of the nucleotide sequence of dNA into comple­mentary sequence in RNA
- transc­ription requires RNA polymerase (enzyme)
- transc­ription -> RNA polymerase binds to DNA and separated DNA strands -> RNA polymerase uses one strand of DNA to assemble strand of RNA
- RNA polymerase only binds into regions of DNA called promoters (indicate where to bind)

RNA Editing

- DNA of eukaryotic genes contains introns (sequences of nucleo­tides) and exons (sequences that code for proteins)

Genetic Code

- proteins made by joining polype­tides (amino acide chains)
- codon: has three consec­utive nucleo­tides that specify a single amino acid that will be added to the polype­ptide
- AUG + start codon
- three stop codons


- transl­ation: decoding of mRNA message into a polype­ptide chain
- transl­ation -> cell uses info from mRNA -> produce proteins
- anticodon bases are comple­mentary to codons
- RNA release into cytoplasm -> mRNA ttatches to cytoplasm -> tRNA brings amino acid into ribosome -> transl­ation begins -> codon breaks -> replaced by anticodon -> polype­ptide chain grows -> newly formed polype­ptide molecule is released -> transl­ation is over

Kinds of Mutations

- mutations are changes in genetic material
- point mutations: changes in one or few nucleo­tides at a single point in DNA sequence
- frameshift mutations: changes that shift the "­reading frame of the genetic messag­e"
- frameshift mutations can change a protein so much that it cannot perform its functions

Signif­icance of Mutations

- mutatios are source of genetic variab­ility in a species
- polypl­oidy: condition in which an organism has extra sets of chromo­somes


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