1. Protein synthesis

2. Beginning with dna
DNA is found in the nucleus, but making a protein occurs at the ribosome (either floating in the cytoplasm or attached to the rough ER
The DNA code must be copied and moved from the nucleus out to the cytoplasm
Once in the cytoplasm, the code must be read so amino acids (building blocks of protein) can be assembled

3. DNA to RNA
In order to get the DNA code out of the nucleus and into the cytoplasm, it must be turned into another nucleic acid called RNA

4. DNA to RNA
RNA does not contain the base thymine – instead it has the base uracil
A goes with U
C goes with G
The RNA molecule is single-stranded

5. types of RNA
Messenger RNA (mRNA) – copies the DNA code and carries the information to the ribosomes outside the nucleus
Transfer RNA (tRNA) – transfers amino acids to the ribosome, where proteins are made

6. Messenger RNA Long, straight chain of nucleotides
Made in the nucleus - copies DNA and then exits out the nuclear pores
Contains the nitrogen bases A, G, C, and U
Carries information for a specific protein
A sequence of 3 bases is called a codon
AUG – start codon (amino acid is methionine)
UAA, UAG, or UGA – stop codons

7. Transfer RNA
Single-stranded molecule with an attachment site at one end for an amino acid
The other end has three nucleotide bases called the anti-codon (complementary to the codon)
amino acid
attachment site U A C
anticodon

8. The Genetic Code
A codon designates a specific amino acid, however an amino acid may have more than one codon
There are 20 amino acids and 64 possible codons
One codon tells the ribosome to start translating (AUG), and three tell the ribosome to stop translating (UAA, UAG, or UGA )

9. The Genetic Code

10. The Genetic Code

11. Pathway to Protein

12. Protein Synthesis The production, or synthesis, of a polypeptide chain
Polypeptide chain = protein
A string of amino acids held together with peptide bonds
There are two phases to making protein – transcription and translation

13. Transcription
DNA  RNA

14. Transcription
The process of copying the sequence of one strand of DNA (the template strand)
mRNA copies the template strand

15. Transcription
Practice: what would be the complementary RNA strand for the following DNA sequence?
DNA 5’ – GCGTATG – 3’

16. RNA 3’ – CGCAUAC – 5’ Transcription
Practice: what would be the complementary RNA strand for the following DNA sequence?
DNA 5’ – GCGTATG – 3’
RNA 3’ – CGCAUAC – 5’

17. TransLATION
RNA  PROTEIN

18. Translation
The process of decoding the mRNA and turning it into a polypeptide chain (protein)
Ribosomes read mRNA 3 bases (one codon) at a time

19. Translation End Product
The end product of protein synthesis is a protein
A sequence of amino acids bonded together with peptide bonds (also called a polypeptide)
aa1
aa2
aa3
aa4
aa5
aa200
aa199

20. Overall Process Primary structure of a protein T A C G DNA A U G C
mRNA
start
codon
codon 2
codon 3
codon 4
codon 5
codon 6
codon 7
codon 1
methionine
glycine
serine
isoleucine
alanine
stop
codon
protein
Primary structure of a protein
aa1
aa2
aa3
aa4
aa5
aa6
peptide bonds

21. Turning genes on and off
Gene Expression
Turning genes on and off

22. Gene Expression
Gene = a specific sequence of nucleotides at a specific spot on a chromosome
ALL body cells contain a complete copy of an organism’s genome (genome = all genes)
What kind of cells do NOT contain a complete copy?
However, not all genes are turned on in all cells
Why?
Each cell transcribes and translates certain genes from the DNA depending on the function of that cell

23. Mutations
When genes change

24. Mutations Mutation means change
There are several different types of mutations that can affect the DNA strand
If the DNA strand is affected, the protein can also be affected?

25. Point Mutations Only a single nucleotide is changed (one point)
This can also be called a substitution mutation
Three things can result from a point mutation
Silent mutation: no change in the amino acid
Missence mutation: a change from one amino acid to another
Nonsense mutation: one amino acid is changed to a STOP codon
May have a smaller impact on the overall protein

26. Point Mutations

27. Frameshift Mutations
Causes a change to the codon where the mutation is located AND to all the codons that come after it
Two types of frameshift mutations
Deletions – removal of a nucleotide
Insertions – addition of a nucleotide
Will likely have a larger impact since it likely changes the whole amino acid sequence (protein)

28. Frameshift Mutations

29. Impact of Mutations
The impact of a mutation on an individual depends on where and when it occurs
If there was a mutation in the DNA of a zygote, how would that impact the individual?
How might a mutation in a skin cell affect an individual?

30. Mutation Examples