1. RiboNucleic Acid (RNA) -Contrast RNA and DNA. -Explain the process of transcription. - Differentiate between the 3 main types of RNA -Differentiate between Introns and Exons -Function of a Promoter

2. What is RNA??? RNA, like DNA, is a nucleic acid that consists of a long chain of nucleotides. RNA stands for RiboNucleic Acid, while DNA stands for DeoxyriboNucleic Acid; the name is based on the sugar. RNA uses the base sequence copied from DNA to direct the production of proteins.

3. Comparing RNA and DNA Each nucleotide in both DNA and RNA is made up of a 5- carbon sugar, a phosphate group, and a nitrogenous base. There are three important differences between RNA and DNA: (1) The sugar in RNA is ribose instead of deoxyribose. (2) RNA is single-stranded, not double-stranded. (3) RNA contains uracil* in place of thymine. *Uracil, like Thymine is a Pyrimidine.

4. DNA vs RNA…

5. Types of RNA The three main types of RNA are: 1. messenger RNA (mRNA) 2. ribosomal RNA (rRNA) 3. transfer RNA (tRNA).

6. Messenger RNA (mRNA) The RNA that carries copies of the DNA’s instructions are known as messenger RNA (mRNA). Their task is to carry information/instructions for protein synthesis from DNA in the nucleus to the ribosome in the cytoplasm.

7. Ribosomal RNA (rRNA) Proteins are assembled on ribosomes. These ribosomes are made up of several ribosomal RNA (rRNA) molecules and as many as 80 different proteins. rRNA molecules are synthesized in the nucleolus region of the nucleus. rRNA molecules are extremely abundant and make up at least 80% of the RNA molecules found in a typical eukaryotic cell. The rRNA binds mRNA to the ribosome and to carry out protein synthesis.

8. Transfer RNA (tRNA) For a protein to be built, a transfer RNA (tRNA) molecule must transfer each amino acid to the ribosome by matching the mRNA’s CODON to the tRNA’s ANTICODON. tRNA has sites for both amino- acid attachment and an anticodon region that binds to a specific sequence (codon) on the mRNA chain through hydrogen bonding. It is a type of non-coding RNA.

9. Transcription The making of the RNA molecule takes place during a process known as transcription. Transcription of an RNA molecule is catalyzed by the enzyme - RNA polymerase. Transcription begins with the binding of the enzyme to a promoter* sequence in the DNA (usually found "upstream" of the desired gene). The DNA double helix is unwound and unzipped by the helicase enzyme. The enzyme then progresses along the template strand in the 3’ -> 5’ direction, creating a complementary RNA molecule that can be “read” in the 5’ -> 3’ direction. The DNA sequence also dictates where termination of RNA synthesis will occur.

10. What are Promoters? Promoters are regions of DNA that promote transcription - in eukaryotes, they are found approximately 30-90 base pairs upstream from the transcription start site. Transcription factors are proteins that bind to these promoter sequences and facilitate the binding of RNA Polymerase.

11. Where does transcription take place? In prokaryotes, RNA synthesis AND protein synthesis take place in the cytoplasm. In eukaryotes, RNA synthesis takes place in the cell’s nucleus and then protein synthesis happens at the ribosomes in the cytoplasm.

12. RNA Editing RNA molecules sometimes require bits and pieces to be cut out of them. The portions that are cut out and discarded are called introns or interrupting segments of DNA (formerly referred to as “junk DNA”). The remaining pieces, known as exons, are then spliced back together to form the final mRNA.