Protein Synthesis

Transcription and Translation

DNADNA

RNARNA

ProteinProtein

Scientists call this the:

Making Proteins

Where are the three

stages of the central

dogma in this

picture?

DNA

mRNA

tRNA

rRNA

protein

I’m DNAI’m

RNA.

How are we

different?

1. RNA is single stranded. DNA is double stranded.2. RNA and DNA has the same bases. But, RNA has

“U” for Uracil, instead of “T” or thymine.

4. The sugar in RNA is called “ribose” instead

of “deoxyribose” in DNA.

3. RNA’s base-pairing rule is A – U and C – G;

while DNA’s base-pairing rule is A – T and C - G

3 types of RNA

mRNA = DNA transcripttRNA = type of RNA that carries the amino acids to the

ribosome

rRNA = RNA that, combined with protein, makes up the

structural component of a ribosome

Making protein involves 2 steps

1. Transcription: creating

mRNA from DNA

2. Translation: creating

polypeptide (protein

polymer) from RNA

First, we’ll study transcription

transcription

DNA

mRNA

translation

polypeptide

ribosome

DNA Transcription

Making mRNA from DNA

To better understand

transcription, let’s first watch

an animation.

Steps for DNA transcription

1. DNA unzips at the gene of interest

2. RNA polymerase (enzyme) matches RNA nucleotide bases to the template strand of DNA, using A – U and C – G rule.

3. The mRNA strand is created and moves out of nucleus to the ribosome in the cytoplasm.

4. DNA zips back up.

Let’s practice being RNA polymerase by

playing CODON bingo!

DNA Translation

Making polypeptide (protein

polymer) from RNA

To better understand translation,

let’s first watch an animation.

Key Players in Translation

rRNA = RNA that makes up a ribosome

tRNA = RNA that transfers specific amino acids

mRNA = RNA transcribed from DNA

Codon = 3 nucleotides in a row on a strand of

mRNA that code for an amino acid

Anticodon = 3 nucleotides in tRNA that base

pair with the codon

Amino Acids = monomers of proteins (20 in humans)

Steps to Translation

Making proteins from mRNA1. Ribosomes attach to the “start” codon of

mRNA (AUG), signaling the start of translation

2. mRNA codons base-pairs with tRNA anticodons. The t-RNAs bring in the appropriate amino acids to be strung together.

3. Dehydration synthesis occurs between the amino acids, and they join, making a polypeptide (protein chain)

4. Ribosomes detach when they come across a “stop” codon (UAA, UAG, UGA). Protein synthesis is complete.

How do you

read an mRNA

table to figure

out the correct

sequence of

Amino Acids?

DNA template:

TAC GGC AAT ACT

mRNA:

AUG

Start – PRO – LEU - Stop

mRNA:

AUG CCG

mRNA:

AUG CCG UUA

mRNA:

AUG CCG UUA UGA

Start –Start – PRO –Start – PRO – LEU -

Amino Acid Sequence:

Translation

Activity

• You and your

classmates need to

discover the

hidden protein in

your bag.

• Follow the

instructions in the

bag to unlock the

mystery protein.

What if a single base is changed?

What if a single base is changed?

What if a single base is changed?

Individual Activity:

Decoding from DNA

On your own, use a slightly different table

to decode the secrets of Foothill.

tttacccatagc

Translation: FTHS