RNATranscription and Translation

Replication

Assemble the DNA

Follow base pair rules

Blue—Guanine Red—Cytosine Purple—

Thymine Green--Adenine

Replication

Assemble the DNA

Follow base pair rules

Blue—Guanine Red—Cytosine Purple—

Thymine Green--Adenine

Flow of information DNA stores information--blueprint.

› Replication to copy the information exactly. DNA to RNA is transcription—job

instructions.› Transcription to make a working template.

RNA to protein is translation—produce final product.› Translation to produce proteins for the cells.

Types of RNA

messenger RNA (mRNA). A copy of the gene that is being expressed.

ribosomal RNA (rRNA). Four different RNA molecules that make up the structure of the ribosome.

transfer RNA (tRNA). Small RNA molecules that act as adapters between the codons of mRNA and amino acids.

mRNA—single strand

mRNA is a complementary single strand that is transcribed from one DNA strand of one gene.

Working instructions to build one protein

One gene one mRNA One mRNA one protein

Editing messenger RNA A gene includes both

coding segments called exons and non-coding segments called introns.

Only exons are read for codons to produce proteins.

Introns are cut out and exons are spliced.

Reading the mRNA

The nucleotides are read in triplets called codons.

Reading starts at AUG, the start codon. Read groups of three until a STOP

codon is reached. Each codon is specific for a single

amino acid. There may be multiple codons for an

amino acid.

Transfer RNA

tRNA is a folded single strand of RNA which is able to bind to an amino acid. tRNA binds to one and only

one amino acid. tRNA has a series of three

nucleotides that make an anti-codon that matches up with the codon on mRNA

Ribosomes

Ribosomal RNA (rRNA) is a single strand RNA that folds.

2-4 rRNA join to make a ribosome

Ribosomes are the site of translation, an assembly machine for proteins.

Translation

Protein Synthesis--Preparation

Preparation: transcription of a gene in the DNA to mRNA

mRNA exits nucleus to cytoplasm.

Initiation Stage Step 1: mRNA joins a ribosome. Step 2: Read AUG start codon Step 3: tRNA brings in attached

amino acids. tRNA matches its anti-codon to the mRNA codon.

Attach methionine

Elongation

tRNA carries in amino acids Attach new amino acid to growing

polypeptide chain. Repeat

Termination--STOP The elongation of the protein continues

until a STOP codon is read by the rRNA. Separate protein from ribosome. Ribosomes, mRNA, tRNA can be

reused.

Amino Acids

64 codons total

1 start 3 stop codesAmino acids 20 amino

acids for humans

Review DNA—getting from data to structure

DNA is an information structure To make something the data needs to be

transcribed to a working template. Transcription is the process of copying

DNA to a messenger RNA, mRNA.› In the nucleus

Translation is the process of converting the data sequence in mRNA into amino acids linked together to make a protein.› In the cytoplasm

Review--Build a Protein

DNA to mRNA: transcription Add rRNA (ribosome) mRNA to protein: translation

› AUGstart: initiation› Use tRNA to transfer the amino acids to

the growing chain› Add amino acids: elongation› STOP: termination