1. DNA Review

2. DNA structure Double helix – two parallel bands that spiral together
4 nucleotides – a molecule made up of a nitrogen base, a sugar, and a phosphate group
Sides of helix – sugar-phosphate group
“teeth” of helix – nitrogen bases
Bases – Adenine pairs with Thymine, Cytosine pairs with Guanine

3. DNA -> Protein
Replication
Transcription
Translation
~ 20,000 genes

4. DNA Replication
1. DNA strand separates and nitrogen bases are exposed.
2. Nucleotides move into place and form new nitrogen base pairs.
3. Two identical pairs of DNA are produced.
How do nucleotides form? We break down food into small of enough pieces for our cells to further break down the food and rearrange the molecules into bases.

6. DNA Transcription 1. mRNA nucleotides pair up with DNA nucleotides.
2. Completed mRNA can move into the cytoplasm
RNA is single-stranded. RNA switches Thymine for Uracil.

7. DNA Translation
1. tRNA (transfer RNA) carries amino acids to the ribosome
2. rRNA (ribosomal) helps form chemical bonds that attach one amino acid to the next
3. The first tRNA separates from its amino acid and from the mRNA. A third tRNA brings in another amino acid.
INITIATION -> ELONGATION -> TERMINATION

8. initiation: start codon (AUG) -> elongation: -> termination: stop codon (UAG)
Let’s make a PROTEIN!!!!.

9. The Code Proteins = arrangements of amino acids
Each series of three nitrogen bases on the mRNA molecule (AUU, AUC, UUG, etc.) is called a codon.
There are 64 codons (4 x 4 x 4) that code for 20 amino acids (some codons code for the same amino acid)
Codons signal where a protein begins and ends (3 codons signal STOP)

10. Cracking the Code
Codons are located on mRNA, Anticodons are located on tRNA.
Codon = three bases on the mRNA molecule (AUU, UGA, CCG, AUA, etc.)
Anticodon = three bases on the tRNA molecule that pair up with the mRNA molecule (if mRNA said UGA, the anticodon would read ACU)
THE CODON CODES FOR THE AMINO ACID, THE ENDS OF THE PROTEIN

11. Cracking the Code Ex. mRNA strand reads:
(AUG, GGU, AUU, AAA, GGG, CUG)
The tRNA anticodon sequence that matches with each codon is:
(UAC, CCA, UAA, UUU, CCC, GAC)
The Amino Acid order comes from the mRNA strand!

12. Question:
The anticodon UAC belongs to a tRNA that recognizes and binds to a particular amino acid.
What would be the DNA base code for this amino acid?

13. Answer:
tRNA - UAC (anticodon)
mRNA - AUG (codon)
DNA - TAC

15. Initiation 2-tRNA 1-tRNA anticodon mRNA hydrogen bonds G aa2 A U U A C

16. Elongation 3-tRNA 1-tRNA 2-tRNA anticodon mRNA hydrogen bonds
peptide bond
3-tRNA G A
aa3
aa1
aa2
1-tRNA
2-tRNA
anticodon U A C G A U A U G C U A C U U C G A
hydrogen
bonds
codon
mRNA

17. 1-tRNA 3-tRNA (leaves) 2-tRNA mRNA aa1 peptide bond G A aa3 aa2 U A C
Ribosomes move over one codon

18. 4-tRNA 2-tRNA 3-tRNA mRNA peptide bonds G C U aa4 aa1 aa2 aa3 G A U G

19. 2-tRNA 4-tRNA (leaves) 3-tRNA mRNA peptide bonds G C U aa4 aa1 aa2 aa3
Ribosomes move over one codon

20. 5-tRNA 3-tRNA 4-tRNA mRNA peptide bonds U G A aa5 aa1 aa2 aa4 aa3 G AC U G C U A C U U C G A A C U
mRNA

21. 5-tRNA 3-tRNA 4-tRNA mRNA peptide bonds U G A aa5 aa1 aa2 aa3 aa4 G AC U G C U A C U U C G A A C U
mRNA
Ribosomes move over one codon

22. Termination aa199 aa200 terminator 200-tRNA or stop codon mRNA aa5 aa4
primary
structure
of a protein
aa200
aa2
aa1
terminator
or stop
codon
200-tRNA A C U C A U G U U U A G
mRNA

23. JUNK DNA? NO!
Noncoding DNA – regulates gene expression, replication, centromeres, and telomeres.
Telomeres – region of reptitive sequences at the end of a chromosome, which protects the end of the chromosome – may prevent genetic material from being replicated and translated

24. MUTATIONS Mutation – a change in the nulceotide sequence of a gene
Can be triggered by X-rays, ultraviolet light, radioactive materials, and some chemicals

25. Types of Mutations
Substitution – Base pair (C-G, for example) has been replaced by A-T
Insertion – Base pairs have been added
Deletion – Base pairs have been removed
Mutations can cause amino acids coded by mRNA to be assembled incorrectly, making proteins function incorrectly or not at all

26. Hereditary and Acquired versions
Hereditary – inherited from parent, present in virtually all cells, error occurs in gametes during development
Acquired – cannot be passed to the next generation, caused by external factors or replicate errors