pter 8 – From DNA to Protein
Jan 21, 2016
Chapter 8 – From DNA to Protein
Old dead people to add to our “Important People” chart
Person Origin Time Frame
Importance
Frederick Griffith
English 1928 “transformation principle”
Oswald Avery
Canadian
1944 Repeated Griffiths experiment – found DNA was transformed
Hershey & Chase
American
1952 Used bacteriophages to verify DNA is genetic material
Frederick Griffith
Oswald Avery
Hershey and Chase
HersheyChase
DNA is a long polymer made up of nucleotides3 parts to a nucleotide
2. Deoxyribose (sugar)
3. Nitrogen base
1. phosphate group
4 nitrogen bases in DNA
1. Adenine (A)2. Guanine (G)
3. Cytosine (C)4. Thymine (T)
Double Ring = Purines
Single Ring = Pyrimidines
Old dead people to add to our “Important People” chart
Person Origin Time Frame
Importance
Erwin Chargraff
Austro-Hungarian
1950 Chargraff’s rule: A=T, G=C
Rosalind Franklin
British Early 1950’s
Took x-rays of DNA which showed an “X” shape
Watson & Crick
American / British
1953 Made a model of DNA with a double helix shape
Erwin Chargraff
Rosalind Franklin
Watson
Crick
Watson and Crick
The sugar and phosphate form the backbone of DNAThe bases stick out
sideways A always pairs with TBase pairing rule:
G always pairs with C
Replication = the process by which DNA gets copied
DNA gets made during the S phase, how?
Possible because of base pairing rules
Each strand is now a templateto build the other “half”
Step 1: DNA helicase “unzips” DNA creates a replication fork
Step 2: DNA polymerase adds free bases to each half of the “unzipped” DNA
The whole process is quick it happens in hundreds of spots at once
Also accurate because DNA polymerase “proofreads”
Central Dogma of biology = info flows one way; DNA RNA Protein
1. Ribose instead of deoxyribose
RNA is like a disposable copy of DNA
2. Single strand instead of a double3. Uracil instead of thymine
3 major differences
Transcription = copying part of DNA to make RNA
Genes, not the whole chromo, get copiedRNA polymerase help the process
along
Step 1: RNA polymerase unwinds DNA at beginning of a gene
Step 2: RNA polymerase adds free bases to new RNA, DNA zips back togetherA pairs with U, C pairs with G
Step 3: New RNA detaches from DNA
3 types of RNA are the possible result; mRNA, rRNA, tRNA
RNA Type
The letter?
Its Job Construction Analogy
mRNA Messenger
Copy of DNA instructions for
cell’s use
Blueprints for the building
rRNA Ribosomal
Makes up ribosomes
The actual build location
tRNA Transfer Transfers the amino acids to the ribosome
The workers bringing supplies
Once mRNA is made its translated into proteinmRNA has 4 bases = 4 letters in
its codeEach “word” (codons) is 3 bases long
There are 64 possible 3-base codons
Some amino acids have more than 1 codon1 codon that acts as a
start code3 codons act as a stop
Step 1: mRNA in the cytoplasm attaches to a ribosome
Step 2: As each codon goes through the ribosome an amino acid is brought by tRNA
tRNA has an anticodon that matches with the codon
Ex. Codon ACG matches anticodon UGC
Step 3: Peptide bonds form between adjacent amino acids – tRNA is available to go get more supplies
Step 4: The amino acid chain grows until a stop codon
Mutations = changes in an organisms DNA
Point mutations happen when one nucleotide is swapped for another
Ex. Frameshifts – insertions/deletions
Chromosomal mutations involve changes in larger parts of the chromoEx. Deletions, duplications, translocations
Mutations can be “neutral”, negative, or even beneficial
Some disrupt normal activity
Some cause genetic disorders
Some cause cancer