1. Protein Synthesis
The production (synthesis) of polypeptide chains (proteins)
Two phases: Transcription & Translation
mRNA must be processed before it leaves the nucleus of eukaryotic cells

2. Pathway to Making a Protein
DNA
mRNA
tRNA (ribosomes)
Protein

3. RNA Differs from DNA DNA has a sugar deoxyribose
1. RNA has a sugar ribose
DNA has a sugar deoxyribose
2. RNA contains the base uracil (U)
DNA has thymine (T)
3. RNA molecule is single-stranded
DNA is double-stranded

4. Structure of RNA
Like DNA, RNA is a polymer of nucleotides. In an RNA nucleotide, the sugar ribose is attached to a phosphate molecule and to a base, either G, U, A, or C. Notice that in RNA, the base uracil replaces thymine as one of the pyrimidine bases. RNA is single-stranded, whereas DNA is double-stranded.

6. Three Types of RNA .
Messenger RNA (mRNA) carries genetic information to the ribosomes
Ribosomal RNA (rRNA), along with protein, makes up the ribosomes
Transfer RNA (tRNA) transfers amino acids to the ribosomes where proteins are synthesized

7. Messenger RNA (mRNA) carries copies of instructions for assembling amino acids into proteins.
The three main types of RNA are messenger RNA, ribosomal RNA, and transfer RNA.

8. Ribosomes are made up of proteins and ribosomal RNA (rRNA).
The three main types of RNA are messenger RNA, ribosomal RNA, and transfer RNA. Ribosomal RNA is combined with proteins to form ribosomes.
Ribosomes are made up of proteins and ribosomal RNA (rRNA).

10. The three main types of RNA are messenger RNA, ribosomal RNA, and transfer RNA.
During protein construction, transfer RNA (tRNA) transfers each amino acid to the ribosome.

11. Protein Synthesis DNA molecule DNA strand (template) 3¢ 5¢
TRANSCRIPTION
mRNA 5¢ 3¢
Codon
TRANSLATION
Protein

12. Genes & Proteins
Proteins are made of amino acids linked together by peptide bonds
20 different amino acids exist
Amino acids chains are called polypeptides
Segment of DNA that codes for the amino acid sequence in a protein are called genes

13. Two Parts of Protein Synthesis
Transcription makes an RNA molecule complementary to a portion of DNA
Translation occurs when the sequence of bases of mRNA DIRECTS the sequence of amino acids in a polypeptide

14. Genetic Code Every three bases on DNA stands for ONE amino acid
Each three-letter unit on mRNA is called a codon
Most amino acids have more than one codon!
The code is nearly universal among living organisms
The fact that the genetic code is about universal in living things suggests that the code dates back to the first organisms on earth and that all living things are related.

15. Notice that in this chart, each of the codons (white rectangles) is composed of three letters representing the first base, second base, and third base. For example, find the rectangle where C for the first base and A for the second base intersect. You will see that U, C, A, or G can be the third base. CAU and CAC are codons for histidine; CAA and CAG are codons for glutamine.

16. Transcription Translation
Transcription occurs when DNA acts as a template for mRNA synthesis. Translation occurs when the sequence of the mRNA codons determines the sequence of amino acids in a protein.
Translation

17. Overview of Transcription
During transcription in the nucleus, a segment of DNA unwinds and unzips, and the DNA serves as a template for mRNA formation
RNA polymerase joins the RNA nucleotides so that the codons in mRNA are complementary to the code in DNA

18. Transcription
DNA is copied in the form of RNA
This first process is called transcription.
The process begins at a section of DNA called a promoter.

19. RNA Polymerase Enzyme found in the nucleus
Separates the two DNA strands by breaking the hydrogen bonds between the bases
Then moves along one of the DNA strands and links RNA nucleotides together

20. RNA
During transcription, RNA polymerase uses one strand of DNA as a template to assemble nucleotides into a strand of RNA.

21. Messenger RNA (mRNA) Carries the information for a specific protein
Made up of 500 to 1000 nucleotides long
Sequence of 3 bases called codon
AUG – methionine or start codon
UAA, UAG, or UGA – stop codons

22. A codon consists of three consecutive nucleotides on mRNA that specify a particular amino acid.
A codon is a group of three nucleotides on messenger RNA that specify a particular amino acid.

23. Messenger RNA (mRNA) Primary structure of a protein 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

24. Copyright Pearson Prentice Hall
The Genetic Code
The genetic code shows the amino acid to which each of the 64 possible codons corresponds. To decode a codon, start at the middle of the circle and move outward.
Copyright Pearson Prentice Hall

25. Transfer RNA (tRNA)
Picks up the appropriate amino acid floating in the cytoplasm
Transports amino acids to the mRNA
Have anticodons that are complementary to mRNA codons
Recognizes the appropriate codons on the mRNA and bonds to them with H-bonds

26. Translation Synthesis of proteins in the cytoplasm
Involves the following:
1. mRNA (codons)
2. tRNA (anticodons)
3. ribosomes
4. amino acids

27. Copyright Pearson Prentice Hall
Translation
Translation is the decoding of an mRNA message into a polypeptide chain (protein).
Translation takes place on ribosomes.
During translation, the cell uses information from messenger RNA to produce proteins.
Nucleus
mRNA
Copyright Pearson Prentice Hall

28. The ribosome binds new tRNA molecules and amino acids as it moves along the mRNA.
Lysine
Phenylalanine
tRNA
Methionine
Ribosome
During translation, or protein synthesis, the cell uses information from messenger RNA to produce proteins. The cell uses all three main forms of RNA during this process.
mRNA
Start codon

29. Protein Synthesis Translation
During translation, or protein synthesis, the cell uses information from messenger RNA to produce proteins. The cell uses all three main forms of RNA during this process.

30. The process continues until the ribosome reaches a stop codon.
Polypeptide
Ribosome
During translation, or protein synthesis, the cell uses information from messenger RNA to produce proteins. The cell uses all three main forms of RNA during this process.