RNA

RNA RNA = RiboNucleic Acid Structural units = nucleotides Nucleotide – 3 part: A sugar – ribose A phosphate group A nitrogen base

RNA Nitrogen Bases – name source for the nucleotides A = adenine U = uracil C = cytosine G = guanine

RNA Types 3 types of RNA: Messenger RNA (mRNA) – carries genetic information from DNA in nucleus to ribosome; three base sequence called a codon Ribosomal RNA (rRNA)- makes up ribosomes, where protein is made Transfer RNA (tRNA)- transfers amino acids from the cytoplasm to the ribosome; its three base sequence is called an anitcodon

Differences between… DNA & RNA Deoxyribose Sugar 2 strands Thymine Remains in nucleus Ribose Sugar 1 strand Uracil Can leave nucelus

Transcription

Transcription DNA  mRNA (occurs in the nucleus) a. The complementary strand of RNA is built by the enzyme RNA Polymerase RNA polymerase binds to & separates the DNA strands at promoter sites Promoter - 3 base sequence that serves as a starting and ending points for RNA to be made

Transcription RNA polymerase uses one strand of DNA as a template to make the complementary strand of mRNA

DNA contains… Introns – nucleotide sequences that do NOT code for proteins   Exons – nucleotide sequences that do code for proteins

RNA polymerase copies both introns and exons, but before mRNA leaves the nucleus… Introns are cut out of the sequence Exons are spliced (glued) back together to form the final mRNA

mRNA travels to the ribosomes (outside of nucleus)