1. DNA → RNA→ Protein Sec. 12.3, DNA, RNA, and Protein
Main Idea—DNA codes for RNA, which guides protein synthesis.
The central dogma of biology:
DNA codes for RNA, which guides the making of proteins (which determines the traits!).
DNA → RNA→ Protein

2. RNA (Ribonucleic Acid)
There are 3 main differences between DNA and RNA:
RNA is single stranded
RNA has ribose sugar
RNA has uracil instead of thymine

3. 3 Types of RNA
Messenger RNA (mRNA)—formed complementary to 1 strand of DNA
Travels from the nucleus to the ribosome to “direct” the making of protein.

4. Ribosomal RNA (rRNA)—associates with ribosomes to “read” the messenger RNA

5. Transfer RNA (tRNA)—small segments that transport amino acids to the ribosome
Amino acids are the subunits (smaller parts) that make up proteins.

6. Transcription Transcription—mRNA is made from DNA
mRNA is made in the nucleus but can leave through the nuclear pores.
mRNA has U instead of T.

7. The Code
DNA is used to make mRNA, and mRNA codes for amino acids that make up proteins.
There are 20 amino acids that are used to make proteins.

8. Amino Acids
Amino acids are coded for by 3-base sequences called codons.
Example—GCG (codon) codes for alanine (amino acid)

9. Since there are 4 bases, there are 64 codons. (43 = 64).
So, most amino acids have more than 1 codon.

10. There are special codons to signal “start” and “stop.”
AUG is the start codon (it also codes for methionine).
UAA, UGA, and UAG are stop codons.

11. Translation
Translation—the mRNA code is read and translated to make protein
tRNA carries amino acids to the mRNA/ribosome unit to join the protein.
tRNA has an anticodon that allows it to temporarily join with mRNA during this process.