1. DNA - Transcription, Translation, and Mutations

2. DNA Two strands coiled called a double helix
Sides made of a pentose sugar Deoxyribose bonded to phosphate (PO4) groups by phosphodiester bonds
Center made of nitrogen bases bonded together by weak hydrogen bonds 2

3. DNA Double Helix “Rungs of ladder” Nitrogenous Base (A,T,G or C)
“Legs of ladder”
Phosphate &
Sugar Backbone 3 3

4. Antiparallel Strands One strand of DNA goes from 5’ to 3’ (sugars)
The other strand is opposite in direction going 3’ to 5’ (sugars) 4

5. DNA P O 1 2 3 4 5 P O 1 2 3 4 5 G C T A 5 5

6. Synthesis Phase (S phase)
S phase during interphase of the cell cycle
Nucleus of eukaryotes
Mitosis
-prophase
-metaphase
-anaphase
-telophase G1 G2 S
phase
interphase
DNA replication takes
place in the S phase. 6

7. DNA Replication Begins at Origins of Replication
Two strands open forming Replication Forks (Y-shaped region)
New strands grow at the forks
Replication
Fork
Parental DNA Molecule 3’ 5’ 7 7

8. Proofreading New DNA
DNA polymerase initially makes about 1 in 10,000 base pairing errors
Enzymes proofread and correct these mistakes
The new error rate for DNA that has been proofread is 1 in 1 billion base pairing errors 8

9. DNA Damage & Repair
Chemicals & ultraviolet radiation damage the DNA in our body cells
Cells must continuously repair DAMAGED DNA
Excision repair occurs when any of over 50 repair enzymes remove damaged parts of DNA
DNA polymerase and DNA ligase replace and bond the new nucleotides together 9

10. The three-base code in DNA or mRNA is called a codon.
DNA, RNA, and Protein
The Code
Experiments during the 1960s demonstrated that the DNA code was a three-base code.
The three-base code in DNA or mRNA is called a codon. 10

11. Central Dogma DNA is copied as RNA – Transcription
RNA uses U instead of T
RNA is read to make proteins – Translation
Read by using the reverse of RNA, similar to DNA’s 2nd strand

12. Each anticodon is complementary to a codon on the mRNA.
DNA, RNA, and Protein
Translation
In translation, tRNA molecules act as the interpreters of the mRNA codon sequence.
At the middle of the folded strand, there is a three-base coding sequence called the anticodon.
Each anticodon is complementary to a codon on the mRNA. 12

13. Activity
The first number tells you where the mutation starts, followed by the number or what is deleted
Ex: 487del7 means starting at base bases are deleted.

14. What Are Mutations? Changes in the nucleotide sequence of DNA
May occur in somatic cells (aren’t passed to offspring)
May occur in gametes (eggs & sperm) and be passed to offspring 14

15. Chromosome Mutations Five types exist: Deletion Inversion
Translocation (don’t worry)
Nondisjunction (don’t worry)
Duplication 15

16. Deletion
Due to breakage
A piece of a chromosome is lost 16

17. Inversion Chromosome segment breaks off Segment flips around backwards
Segment reattaches 17

18. Duplication
Occurs when a gene sequence is repeated 18