1. Review

2. Replication occurs in the S-Phase of Interphase
Two strands are separated by enzymes called helicases
New bases are added to each strand by enzymes called DNA polymerases

3. What do you get?
When Replication is completed, two exact copies of the original DNA molecule are produced
Then the cell is ready for to undergo cell division
Mitosis
Cytokinesis

4. Is it Accurate?
Yes, thanks to enzymes that proofread and repair incorrect DNA
1 error per 1 billion nucleotides
BUT it only takes ONE error to cause a mutation in the DNA

5. DNA Replication

6. DNA vs RNA DNA Sugar Bases Size RNA Sugar Bases Size Deoxyribose
Adenine
Thymine
Guanine
Cytosine
Size
Two Strands (Double Helix)
RNA
Sugar
Ribose
Bases
Adenine
Uracil
Guanine
Cytosine
Size
One Strand
A copy of the DNA called mRNA

7. DNA and RNA

8. Types of RNA Messenger RNA (mRNA) Transfer RNA (tRNA)
The copy of the DNA message for making proteins
Takes it from the nucleus to the cytosol
Transfer RNA (tRNA)
Different kinds
Each bonds to a specific type of Amino Acid
Ribosomal RNA (rRNA)
Makes up the ribosomes where proteins are made

9. Transcription
The process of copying the message on DNA and taking it from the nucleus to the cytosol
Think of it as the Recipe for making proteins
To SCRIBE means to COPY

10. How does it happen?
RNA Polymerase (enzyme) binds to a region of DNA called a Promoter
The DNA molecule separates
Only one strand of DNA is transcribed. This is called the template.
RNA Polymerase adds complementary RNA nucleotides to the template strand
Uracil bonds with Adenine
Cytosine bonds with Guanine

11. When is it Finished?
The process stops when RNA polymerase reaches a DNA region called the termination signal
A specific sequence of nucleotides that marks the end of a gene------the STOP sign
When it reaches the stop sign, it releases the DNA molecule and the newly made RNA

12. Why does DNA have to give the information to RNA?
Because DNA is in the nucleus and cannot leave. It is to big.
Ribosomes are in the cytosol and that is where proteins are made.
mRNA is only one strand big, so it can leave the nucleus.
mRNA is the copy of the information found on DNA.

13. Transcription

14. Protein Synthesis Amino Acids are the building blocks of proteins
There are 20 different kinds
Most of them end in -ine
Each protein is made of one or more polymers called polypeptides
Polypeptide----long chain of amino acids
Peptide Bond----covalent bond holding polypeptide together

15. Codon A specific group of three bases on mRNA
Each codon pairs with a specific Amino Acid
The amino acid is carried by the tRNA which has three bases on it
The bases on tRNA pair up with the bases on mRNA
Each Amino Acid has several codons
Some codons do NOT pair with amino acids. These are the START and STOP codons.

16. Start and Stop Codons AUG UAA, UAG, UGA The universal START codon

17. Translation
The process of making proteins using the message from DNA found in mRNA, and the Amino Acids picked up by tRNA.
It begins when mRNA leaves the nucleus and moves to a ribosome in the cytosol. This is where protein production takes place.
The information that was tranSCRIBED has to be TRANSLATED

18. Anticodon The sequence of three bases found on tRNA
It pairs up with the Codon on the mRNA
Codon pairs with Anticodon

19. Making Proteins Amino Acids are floating in the cytoplasm
They are “transferred” to the ribosome by tRNA
Each tRNA has a region that bonds to a specific Amino Acid
On the opposite end is a loop. It has the anticodon sequence of bases on it.

21. Look at codon sequence

22. Translation---Protein Synthesis

23. Polypeptide Chain An AUG start codon on the mRNA begins the chain
AUG codon pairs with UAC anticodon on the tRNA
tRNA carries the amino acid Methionine and is therefore ALWAYS the first amino acid in a protein, because there is only ONE start codon.

24. How does it stop?
An enzyme in the ribosome speeds up a reaction that binds each new amino acid to the chain.
When the ribosome reaches a STOP codon, the process ends and the polypeptide chain is complete.

25. What is a GENE?
The sequence of mRNA is complementary to a specific region of DNA because they were one bonded.
GENE- The segment of DNA that contains the code (recipe) for making a polypeptide or protein. It is a unit of hereditary information.

26. Review