1. NOTE SHEET 13 – Protein Synthesis

2. What are the “instructions” that are found in DNA?
DNA holds the instructions to build proteins
Proteins are important because they make up many of the structures in an organism and perform many functions
Human DNA holds the instructions to build about 30,000 different proteins!

3. Proteins Determine Traits
It is the presence of specific proteins that give an organism its characteristics and allow it to function
The instructions to build these specific proteins are in the organism’s DNA

4. Why are you a human?
The DNA in all your cells holds the instructions to make the specific proteins necessary to form the structures of and perform the functions of a human organism

5. How are proteins built by a cell?
Cells build proteins out of small molecules called amino acids – the amino acids are bonded together making a long protein chain
Proteins are built at the ribosomes
DNA instructions tell the cell which amino acids to use and where to put them in the chain
Protein Synthesis – the process where cells build protein using instructions stored in DNA

6. What is RNA?
RNA (ribonucleic acid) – a long, single-stranded molecule made out of nucleotides that helps cells build protein
RNA has ribose sugar, and the bases A, C, G, and U (uracil)

7. DNA vs RNA DNA is a double helix, RNA is a single strand
DNA has deoxyribose sugar in its nucleotides, RNA has ribose sugar in its nucleotides
RNA has the nitrogen base uracil (U) instead of thymine (T)

8. There are 3 types of RNA:
messenger (mRNA) – carries a copy of DNA instructions from the nucleus to the ribosome
transfer (tRNA) – brings amino acids to the ribosome and puts them in the correct order
ribosomal (rRNA) – bonds the amino acids together to make a protein chain

9. Building a protein is like building a house…
You need a blueprint (instructions) for the house in the construction office – this is like the DNA in the nucleus
You need a work site to build the house – this is like the ribosome
You need a copy of the blueprint that can travel to the work site – this is like the mRNA
You need workers to deliver the materials to build the house to the job site – this is like the tRNA
You need builders to put all the materials together and make the house – this is like the rRNA

11. Building a protein is like building a house…
The blueprint is copied and the copy is brought to the work site. Workers bring the correct materials to the work site and set them up according to the information in the blueprint. Builders put everything together building the house.
An mRNA copy is made of DNA and the mRNA travels to the ribosome. The tRNA brings the correct amino acids to the ribosome and lines them up according to the information in the mRNA. The rRNA puts the amino acids together forming the protein.

12. What are the 2 steps of protein synthesis?
Transcription – process where DNA instructions are copied in the nucleus
DNA unzips and a mRNA copy is made
Transcription takes place in the nucleus
The mRNA leaves the nucleus and travels to the ribosome

13. What are the 2 steps of protein synthesis?
Translation – process where a protein is built at the ribosome
tRNA “reads” the instructions in the mRNA, brings the correct amino acids to the ribosome and lines them up in the correct order
rRNA bonds the amino acids together making a protein chain
Translation takes place at the ribosome

14. DNA unzips

15. An mRNA copy is made of DNA

16. An mRNA copy is made of DNA

17. An mRNA copy is made of DNA

18. An mRNA copy is made of DNA

19. An mRNA copy is made of DNA

20. An mRNA copy is made of DNA

21. An mRNA copy is made of DNA

22. An mRNA copy is made of DNA

23. An mRNA copy is made of DNA

24. An mRNA copy is made of DNA

25. The mRNA leaves the nucleus and travels to the ribosome

26. tRNA “reads” the instructions in the mRNA, brings the correct amino acids to the ribosome and lines them up in the correct order

27. tRNA “reads” the instructions in the mRNA, brings the correct amino acids to the ribosome and lines them up in the correct order

28. rRNA bonds the amino acids together making a protein chain

29. rRNA bonds the amino acids together making a protein chain

30. A protein is a chain of amino acids just like a word is a chain of letters There are 20 amino acids and there are 26 letters in the English alphabet In order to spell a word you need to know which letters to use and what order to put them in, and likewise, to build a protein a cell needs to know which amino acids to use and what order to put them in

31. If you need to know how to spell a specific word, a dictionary will tell you what letters to use and what order to put them in If a cell needs to build a specific protein, DNA will “tell” the cell what amino acids to use and what order to put them in

32. The Genetic Code
Every 3 bases on an mRNA molecule stands for aan amino acid
These pieces of mRNA are called codons
Each codon in the mRNA tells a cell which of the 20 amino acids to use

33. How To Transcribe
DNA bases: A T C G
Bond with mRNA bases: U A G C

34. How To Transcribe – Example 1
DNA: TAC TCA CGC ATC
mRNA: AUG AGU GCG UAG

35. How to Translate
Every 3 mRNA bases together stand for 1 amino acid in the protein chain – these pieces of mRNA are called codons
Use the amino acid chart to figure out which amino acid each codon stands for

36. How to Translate – Example 1
mRNA: AUG AGU GCG UAG
AUG = Met (start codon)
AGU = Ser
GCG = Ala
UAG = STOP
Protein: Met-Ser-Ala-STOP

37. Transcribe and Translate –Example 2
DNA : TAC TGA ATA CCT CAA GGA GGC ACC TGG ACT
mRNA: AUG ACU UAU GGA GUU CCU CCG UGG ACC UGA
Protein: Met-Thr-Tyr-Gly-Val-Pro-Pro-Trp-Thr-Stop

38. Transcribe and Translate –Example 3
DNA : TAC AAA GGA CGA GTA GTT TAA GCA AGA ATT
mRNA: AUG UUU CCU GCU CAU CAA AUU CGU UCU UAA
Protein: Met-Phe-Pro-Ala-His-Glu-Ile-Arg-Ser-Stop

39. Mutation
Mutation – Any change in the DNA base sequence which leads to a change in a protein. Sometimes mutation are beneficial, but they usually lead to non-functioning or incorrectly functioning proteins.

40. Point Mutation – One base in sequence is changed
Original DNA: TAC AAA GGA CGA GTA GTT TAA GCA AGA ATT
Original Protein: Met-Phe-Pro-Ala-His-Glu-Ile-Arg-Ser-Stop
4th triplet in DNA, first base C changed to G
Mutated DNA: TAC AAA GGA GGA GTA GTT TAA GCA AGA ATT
Incorrect mRNA: AUG UUU CCU CCU CAU CAA AUU CGU UCU UAA
Mutated Protein: Met-Phe-Pro-Pro-His-Glu-Ile-Arg-Ser-Stop
The 4th amino acid is proline instead of alanine

41. Point Mutation

42. Frameshift Mutation – One base added or deleted from the DNA sequence
Original DNA: TAC AAA GGA CGA GTA GTT TAA GCA AGA ATT
Original Protein: Met-Phe-Pro-Ala-His-Glu-Ile-Arg-Ser-Stop
2nd triplet in DNA, first base A deleted
Mutated DNA: TAC AAG GAC GAG TAG TTT AAG CAA GAA TT
Incorrect mRNA: AUG UUC CUG CUC AUC AAA UUC GUU CUU AA
Mutated Protein: Met-Phe-Leu-Leu-Ile-Lys-Phe-Val-Leu
After the second amino acid, the protein is completely different

43. Frameshift Mutation

44. Why is it important to eat protein?
Your body needs 20 different amino acids to make all the necessary proteins
Your body is only able to produce 12 of these amino acids on its own
The other 8 amino acids come from foods you eat that contain protein (meat, nuts, dairy products, beans, etc.) – These are called essential amino acids because you cannot survive without eating them

45. The bottom line about DNA…
No DNA = No Protein = No Cells = No Life
Reproduction is all about passing DNA from one cell to another and from one generation of organisms to the next