RNA & Protein RNA & Protein SynthesisSynthesis

DNA Determines Protein Structure

The genetic information that is held The genetic information that is held in the molecules of DNA ultimately in the molecules of DNA ultimately determines an organism’s traits.determines an organism’s traits.

DNA achieves this control by DNA achieves this control by determining the structure of determining the structure of proteins.proteins.

DNA is the blueprint for protein DNA is the blueprint for protein synthesis.synthesis.

All actions depend on proteins All actions depend on proteins called enzymes.called enzymes.

Enzymes are critical for an Enzymes are critical for an organism’s function because they organism’s function because they control the chemical reactions control the chemical reactions needed for life.needed for life. Within the structure of DNA is the Within the structure of DNA is the information for the complete instructions information for the complete instructions for manufacturing all the proteins for an for manufacturing all the proteins for an organism.organism.

• Proteins fold into complex, three- dimensional shapes to become key cell structures and regulators of cell functions called enzymes.

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

• In fact, enzymes control all the chemical reactions of an organism.

• You learned earlier that proteins are polymers of amino acids.• The sequence of nucleotides in each gene contains information for assembling the string of amino acids that make up a single protein.

RNA like DNA, RNA like DNA, is a nucleic is a nucleic acid. RNA acid. RNA structure structure differs from differs from DNA structure DNA structure in three ways.in three ways. First, RNA is single strandedFirst, RNA is single stranded——it it looks like one-half of a zipper looks like one-half of a zipper ——whereas DNA is double stranded.whereas DNA is double stranded.

RNARNA

The sugar in RNA is ribose; DNA’s The sugar in RNA is ribose; DNA’s sugar is deoxyribose.sugar is deoxyribose.

Both DNA and RNA contain four Both DNA and RNA contain four nitrogenous bases, but rather than nitrogenous bases, but rather than thymine, RNA contains a similar thymine, RNA contains a similar base called uracil (U).base called uracil (U).

Uracil forms a base pair with Uracil forms a base pair with adenine in RNA, just as thymine adenine in RNA, just as thymine does in DNA.does in DNA.

There are three types of RNA that There are three types of RNA that help build proteins.help build proteins.

Messenger RNAMessenger RNA (mRNA), brings (mRNA), brings instructions from DNA in the nucleus instructions from DNA in the nucleus to the cell’s factory floor, the to the cell’s factory floor, the cytoplasm.cytoplasm.

On the factory floor, mRNA moves On the factory floor, mRNA moves to the assembly line, a ribosome.to the assembly line, a ribosome.

The ribosome, made of The ribosome, made of ribosomal ribosomal RNARNA (rRNA), binds to the mRNA and (rRNA), binds to the mRNA and uses the instructions to assemble uses the instructions to assemble the amino acids in the correct the amino acids in the correct order.order.

Transfer RNA Transfer RNA (tRNA) is the supplier. (tRNA) is the supplier. Transfer RNA delivers amino acids Transfer RNA delivers amino acids to the ribosome to be assembled to the ribosome to be assembled into a protein.into a protein.

http://www.youtube.com/watch?v=B6O6uRb1D38

TranscriptionTranscription

In the nucleus, In the nucleus, enzymes make enzymes make an RNA copy of an RNA copy of a portion of a a portion of a DNA strand in a DNA strand in a process called process called transcriptiontranscription..

http://www.youtube.com/watch?v=erOP76_qLWA

TranscriptionTranscription

The main difference between The main difference between transcription and DNA replication is transcription and DNA replication is that transcription results in the that transcription results in the formation of one single-stranded formation of one single-stranded RNA molecule rather than a double-RNA molecule rather than a double-stranded DNA molecule.stranded DNA molecule. The mRNA then leaves the nucleus The mRNA then leaves the nucleus and travels to the ribosome.and travels to the ribosome.

Translation: From mRNA to ProteinTranslation: From mRNA to Protein

The process of converting the The process of converting the information in a sequence of information in a sequence of nitrogenous bases in mRNA into a nitrogenous bases in mRNA into a sequence of amino acids in protein sequence of amino acids in protein is known as is known as translationtranslation..

Translation takes place at the Translation takes place at the ribosomes in the cytoplasm.ribosomes in the cytoplasm.

Translation: From mRNA to ProteinTranslation: From mRNA to Protein

In eukaryotic cells, mRNA is made In eukaryotic cells, mRNA is made in the nucleus and travels to the in the nucleus and travels to the cytoplasm.cytoplasm. In cytoplasm, a ribosome attaches In cytoplasm, a ribosome attaches to the strand of mRNA like a to the strand of mRNA like a clothespin clamped onto a clothespin clamped onto a clothesline.clothesline.

For proteins to For proteins to be built, the be built, the 20 different 20 different amino acids amino acids dissolved in dissolved in the cytoplasm the cytoplasm must be must be brought to the brought to the ribosomes.ribosomes.

This is the role of This is the role of transfer RNA.transfer RNA.

The role of transfer RNAThe role of transfer RNA