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