Biology DNA and Protein Synthesis

Miescher

Discovered nucleic acid in white blood cells of pus (nuclein)

Griffith

Discovered that genes from one cell can be taken in by another cell

Avery & others

Discovered that DNA stores and transmits genetic information (DNA is necessary for transformation)

Hershey and Chase

Concluded that DNA makes up genes using bacteriophages

Chargaff's rules

% of C=G and T=A

Rosalind Franklin (and Wilkins)

Used x-ray diffraction to learn about the coiled structure of DNA

Watson and Crick

Built a 3D model of DNA as a double helix structure

A stands for...

Adenine

C stands for...

Cytosine

G stands for...

Guanine

T stands for...

Thymine

Purines

Adenine and Guanine; Double ring bases

Pyrimidines

Cytosine and Thymine; Single ring bases

antiparallel

Two sides of DNA are_____ based on the location of the carbons on the sugar molecule

OH

3' end has

5' end has

Phosphate

Bases to sugar

Covalent Bond

Sugars to phosphate

Covalent Bond

Nitrogen bases to each other

Hydrogen bond

Helicase

Unzips and unwinds DNA by breaking hydrogen bonds between bases

Topoisomerase

Prevents DNA tangling

Replication Fork

Y shaped region where strands of DNA are replicating

RNA Primase

Marks starting point with primer

Primer

Tells DNA polymerase where to start

DNA Polymerase function 1

Builds DNA by adding 1 nucleotide at a time

DNA Polymerase function 2

Reads 3'->5'

DNA Polymerase function 3

Builds 5'->3'

DNA Polymerase function 4

Proofreads DNA

DNA Polymerase function 5

Removes primer

Ligase

Connects Okazaki fragments together

Okazaki fragment

Small segments of DNA built during construction of the lagging strand

Leading strand

3' side facing the replication fork

Lagging strand

5' side facing the replication fork

Transcription

DNA->RNA; Occurs in the Nucleus

Translation

RNA->Polypeptides; Occurs in the cytoplasm at ribosomes

RNA

Single strand of nucleotides

In RNA, Thymine is replaced by...

Uracil

3 forms of RNA

1. Messenger RNA 2. Ribosomal RNA 3. Transfer RNA

Messenger RNA

Blueprint for protein synthesis; Travels from nucleus to ribosome

mRNA start codon

AUG

Transfer RNA

Translates mRNA code to amino acids

Ribosomal RNA

Makes up ribosomes along with protein

RNA polymerase binds to the...

Promoter

RNA nucleotides bind with complementary nucleotides until RNA polymerase reaches the

Terminator code

Introns

Noncoding sequences; Edited out

Exons

Code for amino acids; Spliced together

TATA box

DNA sequence that starts transcription (Promoter sequence)

5' Cap

Added to the front of mRNA for protection

Poly-A-tail

Added to the back of mRNA for protection

Codon

3 base code on mRNA - codes for amino acid or is a stop signal

How many different kinds of amino acids?

20

How many stop signals?

3 (UAG, UAA, and UGA)

How many possible codons?

64 (61 code for amino acids)

Anticodon

tRNA codon that is complementary to an mRNA codon (no anticodon for stop codons)

Ribosomes

2 subunits that only bind together during translation; Large subunit and Small subunit

mRNA site

Holds mRNA

A(acceptor) site

Holds tRNA with next amino acid for chain

P(peptidyl) site

Holds tRNA with polypeptide chain

E(exit) side

Holds empty tRNA

Initiation step 1

Start codon binds to small subunit of ribosome

Initiation step 2

The 2 Ribosome subunits join together

Initiation step 3

tRNA with anticodon UAC(Methianine) binds to start codon at P site

Elongation step 1

Next tRNA comes to A site

Elongation step 2

Enzyme joins 2 adjacent amino acids together with a peptide bond

Elongation step 3

1st tRNA detatches and moves to E site to be released

Elongation step 4

2nd tRNA slides over to P site bringing mRNA and amino acid chain along

Elongation step 5

New codon in A site is ready for new tRNA

Elongation step 6

Elongation repeats until the stop codon is reached

Termination step 1

Stop codon in A site and release protein attaches

Termination step 2

Ribosome complex splits apart releasing new polypeptide

Polysome

Series of ribosomes reading the same strand of mRNA