1. How cells follow DNA directions on how to make proteins
Protein Synthesis
How cells follow DNA directions on how to make
proteins

2. DNA = the directions in code
Each chain of nucleotides is a line of code
Each chain contains directions for making many different proteins
Each set of directions is
a gene
1 gene = 1 protein =1 trait

3. Steps in making a protein
1) Copy the Directions for one protein onto RNA
(one gene)
Transcription
2) Use the RNA directions to make a protein
Translation

4. 1) Transcription
A) RNA polymerase scans the DNA to find the gene it needs to copy
B) RNA polymerase has 4 jobs
1) unwind the DNA double helix
2) breaks hydrogen bonds to separate chains
3) match RNA nucleotides to the DNA gene
4) fuse the RNA nucleotides together to make a chain of RNA

5. The chain of RNA that is made is called mRNA
Or messenger RNA

6. Messenger RNA Carries coded directions out into the cell.
Where mRNA binds to a ribosome.

7. 2) Translation A) Translates nucleotide code of RNA into
the amino acid code of a protein
B) Takes place in the cytoplasm
C) Is done by a ribosome

8. mRNA
mRNA = chain of nuclotides that make up the coded directions for making the protein
Every 3 nuclotides of mRNA is a codon
Each codon is the code for 1 amino acid

10. Ribosomes Made of 2 subunits.
Subunits bind onto mRNA chain at start codon
3 codons at a time are inside the ribosome
E is for Exit
Codons in P and A sites are the ones being read

11. tRNA bring amino acids to the ribosome
Match the correct amino acid in place by matching their
anti-codon to the
mRNA codon
Fit into the E, P and A sites

12. tRNA Each tRNA only picks up ONE kind of amino acid
tRNA drops off amino acids at the ribosome then moves back into the cytoplasm to pick up another amino acid(but always the same kind)

13. Steps to Translation A) Initiaion 1) Ribosome subunits bond to mRNA
2) tRNA that matches start codon binds at site P

14. 3) tRNA that matches 2nd codon binds at site A
B) Elongation
3) tRNA that matches 2nd codon binds at site A
4) ribosome attaches the 2 amino acids those tRNAs carry to each other by a
peptide bond

15. 5) Ribosome moves down mRNA chain by
one codon
6) the first tRNA
Moves into the E
site and exits
the ribosome

16. 7) the next tRNA moves into place

17. Termination 8) Ribosome moves down mRNA to stop codon
9) Release factors bind to stop codon instead of a tRNA
10) Ribosome, mRNA, tRNAs and protein all break apart

18. Mutations= changes in a cell’s DNA
Caused by:
1) spontaneous errors
2) mutagens: chemicals/radiation
Can happen in body cells (somatic cells) or
In reproductive cells (egg & sperm)

19. Somatic cell mutations
May cause no change = if mutated gene is one that is not use by that particular cell
May cause cell to die
May cause cancer
Not passed on to children

20. Reproductive Cell Mutations
Passed on to children
Every cell of the child is mutated
May cause miscarriage
May cause a genetic disorder in child
May have no effect at all

21. 2 types of mutation Gene mutation = DNA coding error
Chromosome Mutation = change in chromosome number, missing or extra chromosome pieces.

22. Gene Mutations 1) point mutations – change only 1 base pair
a) substitution of 1 nucleotide for another
b) AATT becomes AATG
c) may not cause any change
d) may change 1 amino acid
e) can cause disorder

23. 2) Frameshift mutations- change all the codons
a) insertion
b) deletion
c) THE FAT CAT = HEF ATC AT
d) most always ruins protein

24. 3) tandem repeats – codons repeated over & over
most often ruins protein
more repeats = more problems