The Flow of Genetic Information

From Gene to Protein

It All Begins with DNA• DNA: in the

nucleus• Polymer of

nucleotides– Deoxyribose sugar– Phosphate group

(negative charge)– Nitrogen base (A,T,

C,G)

Importance of Nucleotide Sequences

• Different organisms : different order of nucleotides in DNA strands

• Closely related organisms: order of nucleotides in their DNA is more alike

Central Dogma

Codons• Sequence of 3

bases needed to code for an amino acid

• Amino acids are monomers for proteins

Transcription

• Transcription: DNA to mRNA

• Occurs in the nucleus

Important Aspects of Transcription

• RNA Polymerase : pries DNA strands apart, adds RNA nucleotides (only in a 5’ to 3’ direction)

• Promoter: DNA sequence where RNA polymerase attaches and begins transcription

• Transcription unit: stretch of DNA that is transcribed

For each gene only one DNA Strand is Transcribed

Process of Transcription

Eukaryotic Cells Modify RNA

• 5’ end is capped off with a 5’ cap• 3’ end contains a poly-A tail• Introns (noncoding sequences are

removed)/RNA splicing• Exons are joined together

From Pre-mRNA to mRNA

Transcription Overview

• Transcription occurs in the nucleus, mRNA is transported to cytoplasm

• Transcription results in pre-mRNA and RNA processing yields finished mRNA

Translation

• mRNA brings its message to the ribosome and the message is interpreted by tRNA

Ribosomes• Found in the cytoplasm• Facilitate the coupling of mRNA

codons and tRNA anticodons• Made of 2 subunits: large and small

subunits• Constructed of proteins and rRNA

Ribosome Structure

Translation Overview

Protein Synthesis Overview