Making Sense of DNA

DNA is a code for making proteins

DNA (Gene) Protein Trait

DilemmaDNA

• Contains sequence for protein

• Risky/Dangerous for DNA to leave nucleus

Protein• Made by ribosomes• Ribosomes stuck in

cytoplasm

Solution– SEND MESSENGER!

Step 1- Copy DNA Info on mRNA

• DNA creates a message for the ribosome called mRNA.

• Messenger RNA (mRNA):– Same structure as DNA (except different

type of sugar; ribose instead of deoxyribose)

Step 1- Copy DNA Info on mRNA

• DNA creates a message for the ribosome called mRNA.

• Messenger RNA (mRNA):– Same structure as DNA (except different

type of sugar; ribose instead of deoxyribose)

– Single stranded

Step 1- Copy DNA Info on mRNA

• DNA creates a message for the ribosome called mRNA.

• Messenger RNA (mRNA):– Same structure as DNA (except different

type of sugar; ribose instead of deoxyribose)

– Single stranded– Uracil replaces all the thymines.

Step 1- Copy DNA Info on mRNA

• Write the corresponding RNA strand

TAAGCTACCGAATGGACAACACTTCGACTAAUUCGAUGGUUACCUGUUGUGAAGCUGA

Step 1- Copy DNA Info on mRNA

• Transcription video• http://www.youtube.com/watch?

v=ztPkv7wc3yU

Step 1- Copy DNA Info on mRNA

Similarities between DNA and RNA:1. Sugar and phosphate make up the backbone2. They both have base pairs3. They both carry the same protein messages

Step 2- mRNA leaves nucleus

Step 3- mRNA attaches to ribosome at START codon (AUG)

• Ribosome finds the START sequence in the mRNA: AUG

Remember?

• Ribosome- ___________________

Remember?

• Ribosome- makes protein

Step 4- tRNA brings the correct amino acid

Step 4- tRNA brings the correct amino acid

• Each sequence of 3 bases corresponds to 1 amino acid

• Codon- sequence of 3 bases that codes for an amino acid

Step 4- tRNA brings the correct amino acid

• Transfer RNA (tRNA)- brings amino acids to the ribosome.

(Why sequence of 3?)

• There are 20 common amino acids.• Could you make 20 different combinations

with 2 bases?

• How many different combinations can you make with 3 bases?

Step 5- Amino Acids link to form Protein

Step 5- Amino Acids link to form Protein

• tRNA brings the next amino acid.• Peptide bonds- connect amino acids together to form

a protein• Protein- chain of amino acids that fold into a specific

shape.

Step 6- tRNA reaches STOP codon

• The process continues until the STOP codon: UAG, UAA, UGA

• Then the protein is complete.

Putting it all together

• Video 1

• Video 2

Ticket

1. How does the DNA code get to the ribosome?

2. Which amino acid would match the mRNA code: CCA?

Short cut

Practice

DNA code:TACGTTCGAATT

mRNA code:

Amino acid code:

Project-Based Assessment #3

Project choices:Cancer (any genes)