The Central Dogma

• States: information flows in one direction from DNA to RNA to proteins.

• Includes 3 processes:

• RNA is the link between DNA and proteins.

– Replication– Transcription– Translation

replication

transcription

translation

• Single nucleotide strand

• Sugar: Ribose• 4 Bases:

–A: Adenine–G: Guanine–C: Cytosine–U: Uracil

• U replaces T• Three Types of RNA

• mRNA• Function:

Reads the DNA (ATCG) and carries its message to a ribosome

• Location: Starts in nucleus… moves to ribosome

• tRNA• Function: Transfers amino acids from the cytoplasm to

the ribosome• Ribosome will link amino acids together to form a protein• Location: Cytoplasm

Transfer RNAAmino acidProline

Amino acidSerine

• rRNA• Function: Used to

build ribosomes• Location: Cytoplasm• Ribosome: Makes

proteins

Transcription• Defined: Process of making mRNA from DNA

– Copying of a gene to eventually make a protein.

• Step 1: RNA Polymerase separates the DNA nucleotides

• Step 2: Free floating RNA nucleotides match with the DNAReminder: U replaces T

• Step 3: mRNA breaks free in separate pieces• Step 4: mRNA processing takes place

– Unused portions (introns) are removed and the used portions (exons) bond together

• Step 5: Final mRNA strand travels to ribosome• Step 6: DNA recombines to be used again

Transcription Animation

RNA

polymerase

DNA vs. RNA• Double Stranded• Sugar: Deoxyribose• Bases: A T C G• Location: Nucleus

• Single strand• Sugar: Ribose• Bases: A U C G• Location: Nucleus & Cytoplasm

Replication vs. Transcription• Complex enzymes are used• Base pairing rules guide

replication• A=T, G=C

• Copies DNA• Only one copy of DNA is

made• Location: Nucleus

• Complex enzymes are used• Base pairing rules guide

replication• A=U, G=C

• Copies a gene• Many copies and types of

RNA are made• Location: Nucleus

REview• Name three different ways that DNA and RNA differ.• Which RNA:

– is found inside the nucleus?– transports amino acids to the ribosome?– exits the nucleus to the ribosome?– copies the DNA code?– makes up the structure of ribosomes?

• Perform transcription by using the following piece of DNA. Introns are underlined. Write the final strand of mRNA created.

T A C C G T A C A A T G G G A T C