From Gene to Protein

Transcription & Translation

I. PROTEINS: The NUCLEUS controls the ACTIVITIES in the

cell and the DNA inside is composed of genes that code for certain proteins

_PROTEIN codes for a particular trait or helps perform various activities within the cell or body

The processes explained here will show how the genetic message of DNA is able to leave the nucleus and reach ribosomes which assemble all the proteins

All in all, how you look and the activities of your body is largely determined by the proteins that are made!!

II. STRUCTURE OF RNA

DNA is too big to exit the nucleus, so its code must be read by RNA

RNA is the molecule that will be assembled to help make proteins and the ribosomes

Nuclear Pores

A. RNA: RIBONUCLEIC ACID

1. _SINGLE strand2. Nucleotide:–5 carbon sugar–Phosphate group–Nitrogen base

Pairs: A-U (not T!) C-G

B. 3 Types of RNA:

1. Messenger RNA (mRNA)• Reads DNA code and carries the MESSAGE for

making proteins out of the nucleus to the ribosome

B. 3 Types of RNA: (cont.)

2. Ribosomal RNA (rRNA)• Makes the structure of the RIBOSOME(remember from bio-a that ribosomes are the “workers” of the cell!!)

B. 3 Types of RNA: (cont.)

3. Transfer RNA (tRNA)• Transfers AMINO ACIDS to the ribosome for

protein assembly

III. DIRECTIONS FOR MAKING PROTEINS

A. Transcription happens in the Nucleus

• _MESSAGE of DNA is copied or TRANSCRIBED into mRNA, which can leave the nucleus

III. DIRECTIONS FOR MAKING PROTEINS (cont.)

A. Transcription happens in the Nucleus

• _MESSAGE of DNA is copied or TRANSCRIBED into mRNA, which can leave the nucleus

III. DIRECTIONS FOR MAKING PROTEINS (cont.)

Process of Transcription:

1. DNA UNZIPS

animation

III. DIRECTIONS FOR MAKING PROTEINS (cont.)

2. mRNA is TRANSCRIBED from the DNA message

mRNA bases are grouped into sets of 3 nucleotides called a CODON or triplet code

Codon: triplet code that represents an amino acid that will build a protein

III. DIRECTIONS FOR MAKING PROTEINS (cont.)

3. mRNA BREAKS AWAY from the DNA strand

III. DIRECTIONS FOR MAKING PROTEINS (cont.)

4. mRNA LEAVES the NUCLEUS and enters the cytoplasm to await attachment of the ribosome.

B. Translation:Happens in the cytoplasm, proteins built at ribosomes

Process of READING the mRNA codons and translating them into PROTEINS (by attaching amino acids together)

B. Translation (cont.):Happens in the cytoplasm, proteins built at ribosomes

Process of translation: mRNA leaves the nucleus to the cytoplasm

1. A RIBOSOME (rRNA) ATTACHES to the mRNA, which is the site for constructing proteins

mRNA ribosome

B. Translation (cont.):Happens in the cytoplasm, proteins built at ribosomes

2. mRNA CODONS will be READ by the ribosome

B. Translation (cont.):Happens in the cytoplasm, proteins built at ribosomes

3. A tRNA carrying an AMINO ACID in the cell will base pair its ANTICODON with the complimentary (matching) codon on the mRNA strand

ANTICODON: a codon’s COMPLEMENT that will help bring the correct amino acid to the ribosome

B. Translation (cont.):Happens in the cytoplasm, proteins built at ribosomes

4. Translation begins with a START codon, which is AUGAUG – Methionine…starts the process but

does not make the protein

B. Translation (cont.):Happens in the cytoplasm, proteins built at ribosomes

4. Translation ends when a STOP codon is read

B. Translation (cont.):Happens in the cytoplasm, proteins built at ribosomes

6. When each amino acid joins together at the ribosome, they are LINKED by a PEPTIDE bond which forms the PROTEIN