Protein Synthesis

DNA begins the process

• DNA found inside the nucleus

• Proteins are made inside cytoplasm of cells (through ribosomes)

• Ribosomes may be free in the cystol or attached to surface of rER

• DNA’s code must be copied and taken to cystol

• In the cytoplasm, the DNA code must be read so amino acids can be assembled to make polypeptides

Roles of DNA and RNA

• DNA is the blueprint

• RNA is the disposable copy of a section of the blueprint

RNA differences from DNA

• RNA has a sugar ribose while DNA has sugar deoxyribose

• RNA contains Uracil over Thymine

• RNA is single-stranded while DNA is double-stranded

3 Types of RNA

• Messenger RNA (mRNA)

• Ribosomal RNA (rRNA)

• Transfer RNA (tRNA)

Messenger RNA

• Long straight chain of Nt

• Made in the nucleus

• Copies DNA and that copy leaves through the nuclear pores

• Contains the Nt bases (A,U,G,C)

• Carries info for a specific protein

• Sequence of 3 bases called a codon

Ribosomal RNA

• Single strand of Nt (100 - 3000 long)

• Globular in shape

• Made inside nucleus

• Associated with proteins to form ribosomes

• Site of protein synthesis

Transfer RNA

• Clover leaf shaped

• Single stranded molecule with attachment site at one end for an amino acid

• Opposite end has three Nt bases called the anticodon

Genetic Code

• A codon (3 Nt long) designates an amino acid

• 64 possible codons (20 different amino acids)

• Some codons tell ribosomes to stop translating

• Redundant : Amino Acids have multiple codons that code for them

Codons and Antiocodons

• The 3 bases of an anticodon are complementary to the 3 bases of a codon (EX : Codon - GCC / Anticodon - CCG)

• Start Codon is TAC in DNA - which becomes AUG during transcription and translation

Central Dogma

DNA → pre-mRNA → mRNA → Protein

• Transcription in between DNA and pre-mRNA

• RNA processing in between pre-mRNA and mRNA

• Translation in between mRNA and protein