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Complimentary Base Pairing

Purines (A and G) are always paired with pyrimidines (T and C)

2 nm

Diameter of a DNA molecule

DNA Structure

A polymer composed of nucleotide monomers. Antiparalled strands form a double helix turning in a clockwise direction.

Sugar and Phosphate

Make up the backbone of DNA, and provide support for the nitrogenous bases

Phosphodiester Bonds

The bonds between the phosphate and carbon, or the phosphate and hydroxyl; in DNA

Darwin and Mendel

Worked with pea plants to find out that traits are inherited; determined that some traits are recessive and others dominant through cross-pollination


Erwin, 1944; he moved from physics to biology; he thought that genes were made up of proteins


Johann Friedrich, 1869; discovers acidic 'nuclein' in the nucleus, which is later determined to be DNA.

Views in the 1900s

Scientists thought that proteins were everything, and consequently thought that genes were proteins.


Joachim, 1930s; worked with algae to show that the nucleus controls genetic expression


Frederick, 1928; discovered a transforming factor by chance while looking at pneumonia vaccines; he injected mice with good and bad strands of the virus, discovering that something from the bad strand was able to leak out even when it had been denatured, and still affect the mouse.


Oswald T., 1944; realizes that Frederick's transforming factor was DNA


aka. bacteriophage (a virus that infects bacteria); T-2 and T-4 are types that effect E. Coli

Hershey and Chase

Alfred and Martha, 1952; test to see if viruses carry genetic info on DNA or protein; tagged both protein and DNA with different radioactive atoms to see which one carried on inside the cell; DNA was carried on

Wilkins and Franklin

Used x-ray crystallography (beaming an x-ray through DNA) to determine that DNA took on a helical shape


Erwin; analyzed the ATGC ratios in DNA of different species and determined that they were not all 25% ratios, but that A matched T, and C matched G

Watson and Crick

James and Frances, 1953; theoretical biologists who combined lots of ideas to pull ot all together into today's model of DNA


Consist of a phosphate group, nitrogenous bases, and deoxyribose sugar

Hydrogen Bonds

Connect one nucleotide to another nucleotide

Semiconservative Replication

Each DNA molecule is composed of one parent strand and one newly synthesized stand

DNA Helicase

The enzyme that unwinds double-helical DNA by disrupting hydrogen bonds


The pairing of complementary strands of DNA through hydrogen bonding


Single-stranded binding proteins; proteins that keep separate strands of DNA apart

DNA gyrase

The bacterial enzyme that releives the tension produced by the unwinding of DNA during replication

Replication Fork

The region where the enzymes replicating a DNA molecule are bound to untwisted, single-stranded DNA

Replication Bubble

The region where two replication forks are in close proximity to eachother, producing a bubble in the replicating DNA

DNA Polymerase III

The enzyme responsible for synthesizing complementary strands of DNA during replication

Deoxyribonucleoside triphosphates

Nucleotides; molecules composed of a deoxyribose sugar bonded to three phosphate groups and a nitrogenous base

RNA Primer

Annealed to a region of single stranded DNA in order to initate replication


The enzyme that builds RNA primers

Leading Strand

The new strand of DNA that is synthesized continuously during DNA replication.

Lagging Strand

The new strand of DNA that is synthesized in short fragments, which are later joined together

Okazaki Fragments

Short fragments of DNA that are a result of the synthesis of the lagging strand during DNA replication

DNA Polymerase I

The enzyme that removers RNA primers and replaces the with the appropriate nucleotides during replication

DNA Ligase

The enzyme that joins DNA fragments together


Variable Number Tandem Repeats; repeated base pair sequences; 3 types: telomeres, centromeres, pseudogenes


Non-coding DNA at ends of chromosomes to protect genetic material


Repetitive DNA attaches to spindle fibres


2 types: LINEs and SINEs (long/short Interspersed Nuclear Elements)


Proteins; 8 of these in one nucleosome

Restriction Endonucleases

Molecular scissors, cut DNA at specific base-pair sequences

Sticky Ends

Overhang produced after DNA bonds are broken by restriction enzymes

Blunt Ends

DNA ends are fully paired after being cut by restriction enzymes


Enzyme thats adds a methyl group to a nucleotide in order to prevent it from being 'cut'

Gel Electrophoresis

Separates DNA based on different fragment sizes, and the fact that DNA is negatively charged

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