12.3 DNA, RNA, & Protein

Chain of events:

DNA→ RNA→ Synthesis of ProteinOccurs in ALL living things – from bacteria to humans

RNA – Ribonucleic AcidSingle stranded helixContains ribose sugar (not deoxyribose)Uracil replaces thymine3 types of RNA

1. mRNA (messenger RNA)

2. rRNA (ribosomal RNA)

3. tRNA (transfer RNA)

Messenger RNA (mRNA)Carries genetic information from DNATravel from nucleus to the ribosome Direct protein synthesis

Ribosomal RNA (rRNA)Helps join the mRNA codons to the tRNA

anticodons in the ribosomes. It produce enzymes needed to bond amino acids together during protein synthesis

Transfer RNA (tRNA)Transport amino acids to the ribosome

Transcription- The process of transferring genetic information from DNA to RNA

forms one single-stranded RNA molecule

Steps of TranscriptionStep 1: DNA molecule unzips. RNA polymerase

binds where mRNA will be synthesized.

Step 2: Free RNA nucleotides attach to DNA nucleotides by base pairing

Step 3: mRNA strand breaks from DNA

Step 4: mRNA leaves nucleus and goes to cytoplasm to the ribosomes

Transcription Clip

Codon- 3 base code in DNA or mRNA. Each base of a codon in DNA is transcribed in to the mRNA code.

The order of nitrogen bases in mRNA will determine the type and order of amino acids in a protein

The code is universal - the codons represent the same amino acids in all organisms

Three nucleotides code for one amino acid

Example – UUU codes for phenylalanine

•64 possible codons •20 different amino acids

Codons

Codons

Start CodonAUG

Stop CodonsUGAUAAUAG

Translation- the process of converting the information in mRNA into amino

acid chains (proteins)It occurs at the ribosome in the cytoplasmtRNA - brings amino acids to the

ribosomesEach mRNA codon joins to the correct

tRNA anticodon (complement to the mRNA codon)

the end result of translation is the formation of an amino acid chain (protein)

Steps of Translation

Step 1: tRNA picks up amino acids in cytoplasm and takes to mRNA attached to the ribosome

Step 2: The anticodon on the tRNA connects to the complementary codon on the mRNA strand

Step 3: The amino acids attach to one another by peptide bonds forming long chains

Step 4: When stop codon is reached, translation ends and amino acid strand released

Nitrogen Base Sequence

Quick Molecular Genetic Terminology

Replication= DNA DNA Transcription= DNA RNA Translation= RNA Amino Acids Polypeptide= Chain of amino acids Adenine, cytosine, & guanine= DNA & RNA Thymine= DNA Only Uracil= RNA Only

Transcription/Translation Clip