1. PROTEIN SYNTHESIS AND MUTATIONS

2. Review Questions What organelle makes proteins?
Where do these organelles get their directions?
What are the monomers of proteins?
Can mistakes occur in the DNA?
What are those mistakes called?
What are the two different types of nucleic acids?
What are the monomers of nucleic acids?

3. Protein Synthesis Protein Synthesis occurs in four steps:
Transcription – DNA is re-written into mRNA
mRNA is edited
mRNA leaves the nucleus
Translation – mRNA is read and a protein is made

4. What is RNA? RNA is different from DNA in 3 ways
1) The sugar in RNA is Ribose where in DNA it is Deoxyribose
RNA = Ribonucleic acid
2) RNA is usually single stranded; DNA is double stranded
3) RNA includes the nucleotide
Uracil INSTEAD of Thymine
A – U G-C

5. 3 types of RNA Messenger RNA (mRNA) Ribosomal RNA (rRNA)
Carries the genetic code from the DNA, out of the nucleus, to the ribosomes
Ribosomal RNA (rRNA)
RNA found inside of the ribosomes that make up their structure
Transfer RNA (tRNA)
RNA that carries the amino acids into the ribosomes to make a protein

6. Protein Synthesis
Step 1: Transcription-Copy/re-write/transcribe DNA into mRNA
Step 2: Unimportant parts of mRNA (introns) get taken out of mRNA
Step 3: mRNA leaves the nucleus and goes to the ribosomes
Step 4: Translation- Ribosomes read the mRNA and hook on the correct amino acid

7. Step 1- Transcription Transcribes DNA into mRNA DNA is opened up
RNA polymerase hooks onto DNA
Makes complementary strand of mRNA
A hooks to T
U hooks to A
G hooks to C

8. Transcribe the following DNA strand:
TAGTTAGCCAGT

9. Step 2: Unimportant parts of mRNA are removed
Introns (unimportant parts of mRNA) are removed
Exons are spliced back together

10. Step 3: mRNA leaves the Nucleus and goes to a ribosome

11. Step 4: Translation
Ribosomes hook onto the mRNA and read the mRNA code in groups of 3 nucleotides
Codons-groups of 3 nucleotides
tRNA anticodon matches up with a START codon (AUG) on the mRNA sequence and tRNA begins to bring in the correct amino acids

12. Amino acids hook together by peptide bonds
Codons are read until a stop codon is reached

13. 20 possible amino acids Codons code for one of 20 amino acids
Proteins that are formed are based on the amino acid sequence

14. mRNA-AUGCUAGGCCCA
Figure out the order of amino acids using the mRNA strand above

15. Do the whole process!
DNA: T T A G C G A A T T C A
mRNA:
Amino Acids:

16. To RECAP
The DNA is opened up by RNA polymerase and the DNA is transcribed into mRNA.
Unimportant pieces of RNA called introns are removed from the mRNA, and the exons are spliced together.
The mRNA leaves the nucleus and binds to a ribosome in the cytoplasm.
The ribosome reads that mRNA code in groups of 3 called codons, and tRNA hooks on the correct amino acids that is coded for.
Once a stop codon is read, the polypeptide chain is released and a new protein is formed.

17. Mistakes can OCCUR!!! Mistakes in the DNA are known as mutations.
Not all mutations are necessarily bad, but many are detrimental (harmful)
Two Types of Mutations
Chromosomal mutations-large pieces of the DNA
Gene mutations-Individual nucleotide errors

18. Chromosomal Mutations
Deletion – loss of a piece of chromosome
Duplication – an extra piece of an already existing piece chromosome is produced
Inversion – the direction of parts of chromosome are reversed
Translocation – when part of a chromosome breaks off and attaches to a different chromosome

19. Chromosomal Mutations

20. Chromosomal mutation-Nondisjuction
Nondisjunction- the failure of a chromosome to separate from its homologous pair during gamete formation in meiosis.

21. Nondisjunction in Real Life
Ex: Klinefelter’s syndrome-caused by the nondisjuction of the XX chromosomes during egg formation, causing the boy to end up with XXY

22. Gene Mutations
Point Mutations – gene mutations involving in one or a few nucleotides.
Silent Mutation
Nonsense Mutation
Frameshift Mutation
Missense Mutation

23. 1) Silent Mutations Single nucleotide changes in the DNA sequence.
This nucleotide error, however, does not make a difference because the codon still codes for the same amino acid as it would have before.

25. 2) Nonsense Mutations
Point mutation in a DNA sequence that causes a premature stop codon.
This results in an incomplete protein which usually cannot complete its function.

26. 3) Frameshift Mutation
If a nucleotide is added or deleted, the bases are still read in groups of three, but now those groupings are shifted for every codon that follows.
By shifting the reading frame, frameshift mutations may change every amino acid that follows the point of the mutation.

27. 4) Missense Mutations
Mutation that occurs in an amino acid codon which results in the use of a different, but sometimes chemically similar, amino acid.
The similarity between the two is enough that little or no change is often rendered in the protein structure.

28. Sickle Cell Anemia
Sickle cell anemia is an example of a missense mutation that DOES change the protein .
Substitutes A for T. Results in a defective form of the protein hemoglobin (carries oxygen in the red blood cells), causing the cells to be sickle shaped