1. From DNA to Protein

2. Bellringer 11/4/10
Based on the picture on the board, where does transcription occur?
Where does translation occur?

3. Section 2: Genes and Proteins
The sequence of nucleotides in DNA contain information. This information is used to make proteins
Proteins make cells and regulate their functions.
Proteins are made of subunits/monomers called amino acids
The sequence of DNA nucleotides determine the amino acids used to build proteins

4. RNA-Ribonucleic Acid Full name: Ribonucleic Acid
In base pairing, thymine (T) is replaced by uracil
Function: plays a role in making proteins
RNA Nucleotide Structure:
Ribose (sugar)
Phosphate
Nitrogen bases
A pairs with U
C pairs with G

5. Types of RNA
mRNA: messenger RNA; made from DNA & it carries DNA information from the nucleus to the cytoplasm
rRNA: ribosomal RNA; combines with ribosomes to make proteins
tRNA: transfer RNA; carries amino acids to the ribosomes

6. Types of Bases/Base Pairs
Comparing DNA and RNA
DNA
RNA
Strands 2 1
Sugar
Deoxyribose
Ribose
Types of Bases/Base Pairs
A-T
C-G
DNA – RNA RNA-RNA
A-U U-A
C-G C-G
So why is RNA important? Because DNA is too big to leave the nucleus and it uses RNA to take its message out into the cytoplasm.

7. Transcription Location: Nucleus Purpose: DNA information is
copied into mRNA.
Caused by RNA Polymerase (an enzyme)
DNA is safe in the nucleus
Uses mRNA
To send a message to the cytoplasm

8. FYI: How does this happen?
Unzip one gene in DNA
Match up bases to one side of gene in DNA
A binds with U, C binds with G.
mRNA detaches from the DNA
mRNA moves out of the nucleus and into the cytoplasm
DNA: GAG AAC TAG TAC
RNA: CUC UUG AUC AUG

9. Translation Location: Cytoplasm at the Ribosomes
Purpose: tRNA matches to the mRNA to make a specific amino acid chain which is a protein.

10. How are the Nucleotides of Messenger RNA Translated into a Protein?
Events of translation:
The first three bases of mRNA (codon) join the ribosome. Its usually AUG – considered the start codon).
tRNA brings the “amino acid” down to the ribosome. The three bases on tRNA (anticodon) match the complementary bases on mRNA.
Each tRNA has an amino acid, which is determined by its anticodon. Ex: codon (AUG) is for the amino acid - methionine
The amino acids are joined by polypeptide bonds.
The resulting chain of amino acids are called a PROTEIN.

11. Codons & Anticodons
CODON: mRNA bases needed to call an amino acid to the ribosome
Start codon: AUG and it codes for the amino acid methionine
Stop codon: mRNA that means the end of the AA chain has been reached
ANTICODON - segment of three bases on tRNA that is complementary to the mRNA codon.

12. Practice with Protein Synthesis

13. DNA DNA with DNA mRNA DNA with RNA mRNA with tRNA
Process
Information for process
Product
Type of Base Pairing Required
Replication (synthesis of DNA)
Entire length of double helix
DNA
DNA with DNA
Transcription (synthesis of RNA)
Small part of a DNA strand
mRNA
DNA with RNA
Translation (synthesis of protein)
Protein
mRNA with tRNA

14. But What Happens When Any of These Processes Goes Wrong…

15. Mutations… What is a mutation? Any change in the DNA sequence
What is a mutagen?
Any agent that can cause a change in DNA
How can mutations happen?
Spontaneous mistakes in base pairings
radiation
chemicals
high temperatures

16. Types of Mutations
Point Mutation: a change in a single base (like a substitution)
GAG
CTC CUC Leucine
Correct DNA Correct mRNA Correct AA
GCG
CTC CGC Arginine
A should pair with T, but instead C is mismatched to T
Point mutation mutated mRNA Wrong AA

18. Mutations
Example: Sickle Cell Anemia

19. Frameshift mutation: when one or more bases are added or deleted from DNA.
Correct DNA: ATA CCG TGA
TAT GGC ACT
Correct mRNA: UAU GGC ACU
Correct amino acids: Tyrosine Glycine Threonine
Extra inserted base SHIFTS how we read the codons (3 bases), which changes the amino acids
Frameshift mutation ATG ACC GTG A
in DNA: TAC TGG CAC T
Mutated mRNA: UAC UGG CAC U
Wrong amino acids: Tyrosine Tryptophan Histadine

20. Frameshift Mutations: Insertions

21. Frameshift Mutations: Deletions

22. Chromosomal Mutations
Structural changes in chromosomes
Caused by four types of mistakes

23. Insertion- When a part of a chromatid breaks off and is added to its sister chromatid so that the gene is duplicated

24. Deletion- When a part of a chromosome is left out

25. Translocation & Inversion
Translocation: When a part of the chromosome breaks off and is added to a different chromosome
Inversion: When a part of the chromosome breaks off and is reattached backwards

26. Mutations
Frameshift mutations can have catastrophic effects on genes because ALL the codons that follow the shift will be altered, not just one.
Proofreading enzymes are able to repair some damages to DNA