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AP Bio - DNA Cheat Sheet by

What is a gene?

Accurate Replic­ation
Proof-­reading enzymes
General Stability
Double helix = prevents breaks and mutations
Inform­ation Storage
Nitrogen bases code for amino acids and proteins
Transm­ission Inform­ation
Transc­ription & Transl­ation


1866; Gregor Mendel
Discovered factors (genes), come up with three laws of hereditary
1900; Corren, Tschermak, and Devries
Lead to the redisc­overy of Mendel
1900; Robert Feulgen
Came up with DNA stain, "­feulgen stain" stains red
1902; Sutton and Boveri
Chromo­somal theory of inheri­tance -> genes are located on chromo­somes, narrowed down gene location
1925; Fred Griffith
Studied two type of bacteria. smooth (patho­genic) vs. rough (harml­ess), lead to the discovery of transf­orm­ation (the ability of bacteria to pick up and use genetic material) which allows genetic engine­ering
1930s; Collection of Scientists
Eukaryotic chromosome is 80% protein (where most looked), and 20% DNA, prokar­yotic DNA is 100% DNA
1944; Avery, Macleod, and McCarthy
Used enzymes to destroy different proteins and genetic material, concluded that DNA is the genetic material
1950s; Alfred Hershey and Martha Chase
Radioa­ctively tagged DNA and proteins in bacterial phages, concluded that DNA can be transf­ormed (confirmed Griffith)
1950s; Chargaff
Amount of A = Amount of T, Amount of C = Amount of G (Charg­aff's Rule)
1953; Watson, Crick, Wilkins, and Franklin
Discovered the structure of DNA
1983; Barbara McClintock
Discovered transp­osons (jumping genes)
1992; W.F. Anderson
Human gene therapy with human growth hormones
1992; Kary Mullis
PCR (Polym­erase chain reaction)

Crick's Discovery

"­Cap­" of DNA, keeps it from splitting
Double helix
Allows DNA to be stable
Distance between base pairs
.34 nm
Complete turn
3.4 nm, 10 base pairs
Length of DNA molecules
2 meters
Width of DNA molecules
3 nm
Made up of nucleo­tides
Nucleo­tides are made up of...
Ribose sugar (5C), a phosphate group, and a nitrogen base (A, T, G, C)
DNA is...

RNA Structure

- Single strand
- Ribose sugar (OH on 2')
- Nitrogen bases = A, U, C, G

Central Dogma

DNA ------­->
RNA ------­--->

Central Dogma

3 Theories of DNA Replic­ation

1 completely new double helix, 1 completely new
Double helixes are 1/2 new, 1/2 old
Different parts of the double helix are new and old
Meselson & Stahl
Proved DNA replic­ation was semico­nse­rvative using bacteria cultures and nitrogen isotopes

DNA Replic­ation

Leading Strand
5' - 3'
Lagging Strand
3' - 5'
1) Topios­omerase
Relieves stress, DNA will not break
1) Helicase
Unzips­/un­coils DNA, opens double helix into leading and lagging strand
2) Binding Proteins
Keeps the replic­ation fork open
3) DNA Polymerase
Adds nucleo­tides to the leading strand 3' - 5'
4) Primase
Adds a RNA primer for nucleotide fragments (Okazaki fragments)
5) DNA Polymerase
Will connect to primase, adds nucleo­tides in 3' - 5'
6) DNA Ligase
Connects the new nucleo­tides from DNA polymerase to primer on 5' end, changes primer to DNA
7) Proof Reading Enzymes
Checks base pairs (A-T, C-G)

DNA Transc­ription

Making of a mRNA molecule (5' - 3') from a 3' to 5' DNA molecule
1) Transc­ription Factors (Proteins) attach to a regulatory gene (TATA box)
2) RNA Polymerase will bind to transc­ription factors, open up DNA
3) RNA Polymerase will add nucleo­tides of RNA to form a mRNA molecule, mRNA will hang off of the RNA polymerase
4) Once RNA reaches a stop codon on the DNA; 1) mRNA leaves 2) polymerase moves to the next gene 3) DNA closes
Junk DNA
Leaves nucleus
Poly-A Tail
3' end of mRNA, protects nucleo­tides

DNA Transl­ation

Synthesize a protein using mRNA, rRNA, tRNA, and amino acids
1) First tRNA (amino acid) enters P sire, codon and anti codon are comple­mentary
2) 2nd tRNA (amino acid) enters A site
3) Amino acid on P site forms a peptide bond with the amino acid in the A site
4) RIbosome moves down 1 codon, tRNA remains stationary
Turning off a gene by using a comple­mentary mRNA strand to block mRNA from transl­ation

Genetic Code

4 bases x triplet code = 64 possible combin­ations
1 start code (AUG), 3 stop codons
Many codons equaling 1 amino acid buffers against mistakes

Charac­ter­istics of Genetic Code

Triple Code (Codons)
Commaless = no breaks inbetween
Punctu­ation, stop and start codons
Degenerate = Some amino acids have more than one code
Unambi­guous = Same genetic code can be used in different organisms

Types of Mutations

Lose a base pair
Base pair is added
Different base pair is added
Wrong chromosome number, occurs in cell division, caused when mitotic spindles break


Northern Blotting
Electr­oph­oresis of RNA
Southern Blotting
Electr­oph­oresis of DNA
PCR (Polym­erase Chain Reaction)
1) Take DNA sample less than 2,000 pairs 2) Place in test tube with TAQ polymerase and nucleo­tides 3) Heat tube then cool, heat shock for 7-9 minutes, problem = no proof reading enzymes
Genetic Engine­eri­ng/­Rec­omb­inant DNA
Need a target and a vector (usually bacterial plasmid)
Transgenic Animal
Introd­ucing a gene from an animal into the genome of another species


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