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Chapter 13: RNA and Protein Synthesis
Chapter 13.1 (Pgs. 362-365): RNA
DNA
Protein
Characteristics
Protein Synthesis
Ribonucleic Acid (RNA)
- A nucleic acid that consists of a long chain of nucleotides
- Helps put the genetic code into action
- Part of DNA base sequence turned into RNA
- Helps makes proteins
- Has ribose sugar- Has one strand- Has C, G, A and U (Uracil) bases
RNA
DNA vs RNA
DNA- Has deoxyribose sugar- Has two strands (double-helix)- Has C, G, A, and T bases
Functions of RNA
- Main job: protein synthesis- Controls assembly of amino acids
into proteins
- Disposable copy of DNA segment
- DNA is the master plan and RNA is a copy of that plan
Protein made up of amino acids
Three Types of RNA
- Messenger RNA (mRNA)- Carries information from DNA in
the nucleus to ribosomes in the cytoplasm
- Ribosomal RNA (rRNA)- Combines with protein to form
ribosomes
- Transfer RNA (tRNA)- Transfers amino acids to
ribosomes to help build proteins
RNA Synthesis
- Also called Transcription
- Segments of DNA serve as templates to produce complementary RNA molecules
- Occurs in the nucleus
- Requires the enzyme RNA polymerase
- Adds RNA nucleotides
Transcription
1) Initiation- RNA Polymerase binds to DNA and separates DNA
strands
2) Elongation- RNA Polymerase adds base pairs- Uses one strand of DNA as a template- Uracil (U) replaces T on RNA strand
3) Termination- RNA Polymerase stops adding nucleotides- Forms one complementary strand of RNA
4) Editing- RNA molecule is edited before used
Promoters
- Regions of DNA that have specific base sequences
- Tells RNA Polymerase where to start/stop making RNA
- RNA binds to promoter and starts adding complementary bases
Editing the RNA Strand
- Completed RNA molecule needs to be modified before becoming a protein
- Called pre-mRNA
- Little pieces, called introns, are cut out of the mRNA strand and discarded
- Remaining pieces, called exons, are re-connected back together- Protective cap and tail put on either end
