Section 11-2Section 11-2

From DNA to ProteinsFrom DNA to Proteins

Enzymes control all the chemical Enzymes control all the chemical reactions of an organismreactions of an organism

Thus, by encoding the instructions form Thus, by encoding the instructions form making proteins, DNA controls cells.making proteins, DNA controls cells.

RNA vs. DNARNA vs. DNA

DNA:DNA: Double StrandedDouble Stranded

Sugar is DeoxyriboseSugar is Deoxyribose

Contains Thymine to Contains Thymine to pair with Adeninepair with Adenine

RNA:RNA: Single StrandedSingle Stranded

Sugar is RiboseSugar is Ribose

Contains Uracil to Contains Uracil to pair with Adeninepair with Adenine

RNA takes RNA takes instructions from instructions from DNA on how to DNA on how to assemble proteins assemble proteins and then they and then they assemble the protein assemble the protein one amino acid at a one amino acid at a time.time.

3 Types of RNA3 Types of RNA

Messenger RNA (mRNA) – bring the Messenger RNA (mRNA) – bring the information from the nucleus to the information from the nucleus to the cytoplasmcytoplasm

Ribosomal RNA (rRNA) – makes up Ribosomal RNA (rRNA) – makes up ribosomesribosomes

Transfer RNA (tRNA) – transports amino Transfer RNA (tRNA) – transports amino acids to the ribosome to be assembled acids to the ribosome to be assembled into a protein.into a protein.

TranscriptionTranscription Occurs in the nucleusOccurs in the nucleus Changes DNA to RNAChanges DNA to RNA

1. Enzymes unzip the DNA molecule1. Enzymes unzip the DNA molecule

2. Free RNA nucleotides pair with 2. Free RNA nucleotides pair with complementary DNA nucleotides on one complementary DNA nucleotides on one of the DNA strands.of the DNA strands.

Transcription cont.Transcription cont. 3. When the process of base pairing is 3. When the process of base pairing is

completed, the mRNA breaks away as completed, the mRNA breaks away as the DNA strands rejoin. The mRNA the DNA strands rejoin. The mRNA leaves the nucleus and enters the leaves the nucleus and enters the cytoplasm.cytoplasm.

DNA to RNADNA to RNA

DNA: T G A T C G C T ADNA: T G A T C G C T A

RNA: A C U A G C G A URNA: A C U A G C G A U