Griffith
First major experiment searching for generic material that involved transformation between two forms of S pneumoniae.
Avery
Identified the molecule that transformed the R strain of S pneumoniae into the S strand and concluded that when S cells were killed DNA was released.
Hershey and Chase
Used radioactive labeling to trace bacteriophage DNA and protein and concluded that bacteriophage DNA was injected into the cell and provided genetic information to produce new viruses.
Nucleotides
Subunits of nucleic acids that consist of 5-carbon sugars, the phosphate group, and nitrogenous bases
Chargaff
Analyzed the amount of A, G, T, and C in the DNA of various species.
Chargaff’s rule
C=G, T=A
Scientists who searched for the structure of DNA
Rosalind Franklin, Maurice Wilkins, Francis Crick, and James Watson
X-ray diffraction
Indicated DNA was a double helix formed by two strands of nucleotides twisted around each other
Watson and Crick
Using others data, they measured the width of the helix and the spacing of the bases and build a model
DNA structure
A double helix like rails of a ladder represented by the alternating deoxyribose and phosphate
DNA molecule orientation
top rail: 5’ to 3’, bottom rail: opposite direction 3’ to 5’
Prokaryote chromosome structure
DNA molecules are contained in the cytoplasm, and consist mainly of a ring of DNA and proteins
Eukaryote chromosome structure
DNA is organized into individual chromosomes
Nucleosome
DNA and histones which group together into chromatin fibers, which supercoil to form a chromosome
Semiconservative replication
parental strands of DNA sperate, serve as templates, and produce DNA molecules, that have one strand of parental DNA and one strand of new DNA
Processes of semiconservative replication
unwinding, pairing, and joining
Unwinding
DNA helicase unwinds the helix, breaking down the hydrogen bonds between bases, single-stranded binding proteins keep the DNA strands separate, and RNA primase adds a short segment of RNA primer
Base pairing
DNA polymerase adds appropriate nucleotides to the new DNA from the 3’ end while the leading strand is built continuously, the lagging strand is built discontinuously
Okazaki fragments
small segments of the lagging strand build discontinuously
Joining
DNA polymerase removes the RNA primer and fills in the place with DNA nucleotides and DNA ligase links the two segments
Eukaryotic DNA replication
DNA unwinds in multiple areas as DNA is replicated
Prokaryotic DNA replication
the circular DNA strand is opened at one origin of replication
RNA
a nucleic acid similar to DNA, but with the sugar ribose and uracil instead of thymine
Messenger RNA (mRNA)
long strands of RNA that are formed complementary to one strand of DNA; direct synthesis of a specific protein
Ribosomal RNA (rRNA)
Associates with proteins to form ribosomes in the cytoplasm
Transfer RNA (tRNA)
Smaller segments of RNA that transport amino acids to the ribosome
Transcription
the process that involves the synthesis of mRNA from DNA
RNA polymerase
an enzyme that regulates RNA synthesis by binding to the specific section where an mRNA will be synthesized
Introns
DNA sequences not found in mRNA
Exons
DNA sequences that remain in the final mRNA
Codon
the three-base code in DNA or mRNA found in experiments performed in the 1960s
Translation
the process where the mRNA code is read and translated into a protein where tRNA molecules act as interpreters of the mRNA codon sequence
Ribosome
organelle that provides a site for protein synthesis that holds the mRNA in place for translation and grooves for tRNA sites for amino acid attachments
Beadle and Tatum experiment
one gene codes for one enzyme
Gene regulation
the ability of an organism to control which genes are transcribed in response to the environment
Operon
a section of DNA that contains the genes for the proteins needed for a specific metabolic pathway
Operators
on/off switch in operons
Promoter
in operons where RNA polymerase binds
trp operon
a responsible operon that controls tryptophan synthesis
lac operon
an inducible operon when lactose is present E coli can synthesize an enzyme to use as an energy source
Transcription factors
ensure that a gene is used at the right time and that proteins are made in the right amounts
Complex structure of eukaryotic DNA
regulates transcription
Hox genes
A group of genes that control cell differentiation that are transcribed at specific times in specific places on the genome and control what body part will develop at a given body location
RNA interference (RNAi)
can stop the mRNA from translating its message by single-stranded small interfering RNA and protein complexes binding to the mRNA
Mutation
a permanent change that occurs in a cell’s DNA
Point mutation
mutation involving chemical change to just one base pair
Missense substitutions
DNA codes for the wrong amino acids
Nonsense mutation
In a mutation when a codon for amino acid becomes a stop codon
Insertion/deletions
additions/loss of a nucleotide to the DNA sequence that causes “frameshifts”
Mutagens
certain chemicals and radiation that can damage DNA
Mutations in sex cells
mutations passed on to the organism’s offspring and will be present in every cell of the offspring causing an entire person’s cells to have the mutation