2. Transcription
From DNA to RNA

3. Transcription- Where does this happen?
Where is the DNA?

4. Transcription- how RNA is made
location= nucleus
RNA polymerase runs along DNA strand in nucleus and makes RNA (mRNA)
mRNA = messenger RNA (sends message outside of nucleus)
mRNA leaves nucleus through a nuclear pore and meets up with a ribosome (rRNA) in the cytoplasm

5. Translation
From RNA to Protein

6. Translation- Where does this happen?
Where is the DNA?
Protein synthesis – the manufacture of proteins
Where are proteins made in the cell?

7. Translation- how proteins are made
location= ribosome in cytoplasm
Once mRNA is at a ribosome (rRNA), amino acids are assembled to make proteins
Transfer RNA (tRNA) brings the appropriate amino acid to the growing protein chain

8. Genetic Code
Genetic code – the language of mRNA instructions (blueprints)
Read in three letters at a time
Each letter represents one of the nitrogenous bases: A, U, C, G
Codon found on mRNA; consists of three bases (one right after the other)
64 codons for 20 amino acids
mRNA carries the codon (three base sequence that codes for an amino acid)
tRNA carries the anticodon which pairs up with the codon
tRNA brings the correct amino acid by reading the genetic code

9. Codon (cont’d) For example, consider the following RNA sequence:
UCGCACGGU
The sequence would be read three base pairs at a time:
UCG – CAC – GGU
The codons represent the amino acids:
Serine – Histidine - Glycine

10. Codons (cont’d) AUG – start codon or Methionine
UAA, UAG, UGA – stop codons; code for nothing; like the period at the end of a sentence

11. Protein formation Amino acids link together to form a protein
The new protein could become cell part, an enzyme, a hormone etc.

12. Translation
CODON
ANTI CODON

13. SO: Say the mRNA strand reads: tRNA would bring the amino acids:
mRNA (codon) AUG–GAC–CAG-UGA
tRNA (anticodon) UAC-CUG-GUC-ACU
tRNA would bring the amino acids:
Methionine-Aspartic acid-Glutamine-stop

14. SUMMARY
1)mRNA is transcribed in the nucleus and leaves the nucleus to the cytoplasm 2) mRNA attaches to the ribosome 3) The codon on the mRNA is read by the anticodon on the tRNA 4) tRNA brings the amino acid as it reads mRNA 5) The amino acids are joined together to form a polypeptide (protein) 6) When a stop codon is reached (UAA, UAG, UGA) protein synthesis stops

15. What if things go wrong? MUTATION!!!
If transcription or translation were to copy the wrong sequence, the incorrect amino acid could be added
This would change the overall protein structure and could make the protein ineffective
Example: Sickle cell anemia is caused by a single amino acid difference in the hemoglobin protein sequence

16. Gene Mutations
Point Mutations – only occur at a single point in the DNA sequence – only changes a few amino acids
Frameshift Mutations – shift the entire “reading frame” – change ALL the amino acids
Substitution – one base replaces another
Insertion – an extra base is inserted
Deletion – loss of a single letter (makes entire base disappear!)

17. Deletion
Substitution
Insertion

18. Chromosomal Mutations
Change in the number or structure of chromosomes
Ex. – Deletion, Duplication, Inversion, and Translocation

19. Deletion
Duplication
Inversion
Translocation