Watson and crick
Discovered DNA double helix structure
DNA structure
Double helix
Adenine guanine cytosine uracil
Nucleotides made of a 5 carbon sugar, nitrogen base, phosphate group
Nucleotides
Subunits of nucleus acids (DNA AND RNA)
Made of nitrogen base, 5 carbon sugar, phosphate group
Complementary bases
In DNA:
A-T
C-G
In RNA:
A-U
C-G
Complementary bases ratio
1:1 pyrimadine to purine bases
Pyramadines are uracil, thiamine and cytosine, purines are adenine and guanine
Pyrimadine
Uracil, thiamine, cytosine
Purine
Adenine, guanine
Radioactive bacteriophages
Help determine whether genetic material is DNA or protein based using the redioactive tags
Chromosome packaging
DNA wraps around histones, making chromatin
Histones
Proteins which DNA wraps around in the cells in order to condense-> becomes chromatin
Nucleosomes
A unit of chromatin containing 9 histones
Promoter
DNA sequences located in the 5’ region. RNA polymerase binds to the promoter to initiate production of an mRNA transcript.
Codons
In MRNA, group of 3 nucleotides which make up an amino acid
Anticodons
On TRNA, the compliment of the codons on the other side
Start codons
AUG
Mutations
Point mutations, deletions, substitutions, additions
Point mutations
When only one “point” on the DNA is effected, usually changes only one codon and doesn’t have extremely drastic effects on the whole protein
deletion mutations
When one base is deleted from the DNA, usually causes a shift in reading frame effecting all of the DNA that comes after and changing the codon that are read
Substitution mutations
When one nucleotide is substituted with another, (ex A is switched to U) and the codon is changed as a result, doesn’t cause the most drastic results in the protein as it only effects one codon.
Addition mutation
When an extra base is added to the DNA, also causes a shift in the reading frame and can result in drastic changes in the protein
Causes for mutations
Environmental factors such as chemicals, radiation, and ultraviolet light from the sun can cause mutations. These mutagens alter DNA by changing nucleotide bases and can change the shape of DNA
mutations are caused by errors made during mitosis and meiosis . Common errors that occur during cell division can result in point mutations and frame shift mutations. Mutations during cell division
Transcription
DNA directed synthesis of RNA:
- Initiation
- Elongation
- Termination
Initiation of Transcription
RNA transcription starts at a promoter sequence
`Elongation of transcription
Strand gets longer through the unwinding of DNA
Termination of transcription
strand stops transcription, new RNA transcript is released and polymers detach.
In a eukaryotic cell, pre-mRNA is modified, 5’ end gets a nucleotide ADN 3’ end gets a poly-A tail
RNA Splicing
RNA splicing removes introns, joins exons together
Usually carried out by splicsosomes which are made out of protein and work to break bonds and remove the intros
exons
Code for different parts of a protein-> the part of the RNA that is left in
How mRNA is synthesized (ie transcription)
RNA polymerase goes down the DNA, synthesizing the complementary strand
New nucleotides are added to the 3’ strand
rezips previous stretch of DNA as it moves down
TRNA
(transfer RNA)
Picks up specific amino acids, brings them to the right position on the codon
Has an ANTIcodon on one end (the opposite of the codon its going to) and a specific amino acid on the other end
Structured like a clover leaf
translation
Steps:
- Initiation
- Elongation
- Termination
Initiation of translation
stars with a start codon on RNA, brings together MRNA and tRNA with amino acids and ribosomes subunits
Free ribosomes intiate protein synthesis
Elongation translation
Amino acids are added to build a protein, peptide bond forms between amino acids
Termination translation
When the ribosome reaches a stop codon (UGA, UAA, UGA) the polypeptide molecules are released not cytoplasm
Lyctic cycle
Meaning “to escape”
Main type of virus replication
Eventually makes infected cells burst, releasing the virus to other cells
lysogenic cycle
Meaning “creating lyctic”
Injects DNA, sits in bacteria and continues to be co-pied in bacteria forever, EX is te cold sore virus which sits in bacteria forever
bacteriophage
A bacteriophage /ˈbækˈtɪər.i.oʊˌfeɪdʒ/ (informally, phage /ˈfeɪdʒ/) is a virus that infects and replicates within a bacterium.