1. From DNA to Proteins
Lesson 1

2. Lesson Objectives State the central dogma of molecular biology.
Describe the structure of RNA, and identify the three main types of RNA.
Give an overview of transcription.
Describe the genetic code.
Explain how translation occurs.

3. Central Dogma of Biology
DNA is found in chromosomes.
eukaryotic cells, chromosomes always remain in the nucleus
proteins are made at ribosomes in the cell
How do the instructions in DNA get to the site of protein synthesis outside the nucleus?
Another type of nucleic acid is responsible.
RNA, or ribonucleic acid
RNA is a small molecule that can squeeze through pores in the nuclear membrane

4. Central dogma of molecular biology
RNA carries the information from DNA in the nucleus to a ribosome in the cell and then helps assemble the protein
Central dogma of molecular biology
DNA → RNA → Protein
the phase itself was coined by Francis Crick

5. RNA and Protein Synthesis
Genes are coded DNA instructions that control
the production of proteins within the cell.
RNA molecules then carry out processes of making
proteins.

6. Structure of RNA Backbone => 5-C sugar and phosphate group
DNA  deoxyribose
RNA  ribose
Single- stranded
DNA  double-stranded
4 Nitrogenous bases
Adenine
Uracil
Cytosine
Guanine
Note: Change in Nitrogenous bases…What do you think Uracil pairs up with????
In essence RNA is a disposable copy segment of DNA; usually a working copy of a single gene
Thus a single gene can produce 100s or 1000s of RNA molecules from the segment of DNA

7. Types of RNA 3 main types of RNA messenger RNA (mRNA)
Carry copies of instructions for assembling amino acids into proteins
Keep in mind the major job of RNA is protein synthesis (the making of proteins)
What is the monomer of a protein????????
IT also controls the assembly of amino acids into proteins…

8. ribosomal RNA (rRNA) Proteins are assembled on ribosomes
What are ribosomes made of? Several dozen proteins and ribosomal RNA

9. transfer RNA (tRNA)
Transfers each amino acid to the ribosomes as specified by the coded message of mRNA

10. Recall replication makes a complementary copy of the
entire DNA molecules before
cells reproduce or divide
What does it mean to transcribe something? Write a copy of it….DNA is transcribed to produce a molecule of RNA

11. Transcription
RNA molecules are complementary copies of part of a nucleotide sequence in DNA that are made through the process of transcription
RNA polymerase
catalyzes
transcription
During transcription, RNA polymerase binds to DNA and separates the DNA (unzips it partially) strands. RNA polymerase then uses one strand of the DNA as a template from which nucletides are assembled into a strand of RNA.

12. sites known as promoters
RNA polymerase binds
to DNA at very specific
sites known as promoters
promoters have specific
base sequences to start
and stop transcription
Where is DNA located in eukaryotes? Nucleus
Where does transcription take place? Nucleus

13. RNA Editing
Compiles the final mRNA molecule after many eukaryotic genes are transcribed
Introns pieces that are removed
Removed while RNA molecule still in nucleus
Exons remaining portions
Spliced back together to form final mRNA
Where do you find rRNA molecules?? Ribosomes
rRNA molecules are produced from larger RNA molecules that are cut and trimmed to their final size through the process of RNA editing.
What happens to the introns? Biologists suggest they may play a role in evolution; making possible small changes in DNA sequences

14. The Genetic Code
Proteins made by joining amino acids into long chains called polypeptides.
Each polypeptide contains a combination of any or all 20 amino acids
Properties of proteins determined by order in which amino acids are joined together

15. Reading the Genetic Code
‘Language’ of mRNA is the GENETIC CODE
RNA  4 different nitrogenous bases:
A, U, C, G
Genetic Code is read 3 letters at a time
Each ‘word’ is 3 bases long
Each 3 letter ‘word’ in mRNA is known as a  codon
The 4 nitrogenous bases write for 20 amino acids
Codons consists of three consecutive nucleotides that specify a single amino acid that is to be added to a polypeptide

16. Examples of Genetic code
RNA sequence
UCGCAGGGU
Read 3 bases at a time
UCG- CAG- GGU
UCG = Serine
How many possible combinations (codons)? 4 bases; 3 letters each codon= 4 x 4 x 4 = 64
Handout codon wheel ….explain decode my codons above
What amino acid is specified by CAU? Histidine
Codon for tryptophan? UGG
Codon(s) for glutamine? CAG, CAA
Notice some amino acids have more than one codon
Look at AUG= only Methionine or ‘start’ codon
There are 3 ‘stop’ codons= UAA, UAG, UGA
HANDOUT Quick LAB
HANDOUT: Similarities & Differences between DNA & RNA = Homework
CAG = Glutamine
GGU = Glycine

17. Translation
Ribosomes read mRNA and put together polypeptides decoding= translation
Translation takes place on the ribosomes
Cell uses information form messenger RNA to produce proteins; protein synthesis

18. Recap of Transcription/ Translation
mRNA transcribed (CLICK, click) from DNA in nucleus and released to cytoplasm (CLICK, click)
Translation begins when mRNA molecule in cytoplasm attaches to a ribosome (CLICK, click). As each codon moves through the ribosome, proper amino acid is brought into the ribosome and attached to the growing polypeptide chain (CLICK, click. Ribosome does not know which amino acid to match to each codon. Transfer RNA does that job; each tRNA molecule has an amino acid attached to one end (CLICK) and a region of three unpaired bases at the other end. The three bases on the tRNA molecule called anticodon & are complemetary to one of the mRNA codons. (CLICK).
Ribosomes form a peptide bond between the first and second amino acids, then at the same time breaks the bond that had held the first tRNA molecule to its amino acid and releases the tRNA molecule. Ribosome then moves to 3rd codon, tRNA brings its amino acid etc.
Polypeptide chain continues to grow until ribosome reaches a stop codon on mRNA molecule. Ribosome releases newly formed polypeptide and the mRNA molecule…translation is complete… new protein synthesized
GO TO HIPPOCAMPUS SHOW ANIMATION…..
HANDOUT: Making a protein= Homework

19. The Roles of RNA and DNA DNA “ master plan” RNA “blueprints”
Remains in nucleus
RNA “blueprints”
Goes to protein-building sites in cytoplasm
ribosomes

20. Genes and Proteins
Most genes contain only instructions for assembling proteins
Genes that code for enzymes can produce pigments for eye color, etc.
Other enzyme-coding genes produce your red blood cell surface antigen thus determining your blood type
Genes can also regulate rate of growth
Many proteins are enzymes, which catalyze and regulate chemical reactions
Proteins are the key to almost everything living cells can do