Chapter 13: RNA and Protein Synthesis. Chapter 13.1 (Pgs. 362-365): RNA.

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