Transcription and Translation
Structure of RNA
• Similar to DNA
• 5 carbon sugar
• Phosphate group
• Nitrogenous base
• 3 main differences
• Ribose sugar rather than deoxyribose
• Single stranded rather than double stranded
• Bases are Adenine, Uracil, Guanine, Cytosine
• Disposable copy of DNA
Types of RNA
• mRNA
• The message of DNA to code for a gene
• tRNA
• Used to bring amino acids together when creating proteins
• rRNA
• Forms ribosomes, along with proteins
Transcription
• Production of RNA from DNA
• Requires RNA polymerase
• Function?
• Started by helicase proteins
• Promoters
• Regions of DNA that allows RNA polymerase to bind to it
• Signal points for the beginning of a gene
After Transcription
• RNA produced requires editing before it is an active form
• Introns: sequences of DNA found in eukaryotic genes
• Must be removed from RNA before it can be used to produce proteins
• Exons: segments of DNA that code for proteins
• Stay in DNA
• Both introns and exons are formed from DNA
Genetic Code
• Amino acids are joined together in long chains to form proteins
(polypeptides)
• Each combination of amino acids means the proteins have different
properties
• Codon
• Three nucleotides that code for a specific amino acid
• mRNA is read 3 bases at a time, each 3 bases is one codon
• UCGCACGGU  UCG-CAC-GGU  Serine – Histidine – Glycine
Translation
• Turning mRNA into a protein
• Requires ribosomes
• Occurs in 3 steps
• mRNA in cytoplasm attaches to a ribosome. mRNA moves through the
ribosome, each codon is read and a tRNA brings the matching amino acid and
attaches them together.
• Peptide bond is formed between amino acids to hold protein together. At the
same time, ribosome breaks the bond holding the amino acid to the tRNA
then releases the tRNA.
• Continues to grow until the ribosome reads a stop codon
Genes and Proteins
• Proteins control every physical characteristic
• Genes control production of enzymes to produce skin pigment
• Genes also control enzyme production that determines blood type
Activity
• Make a drawing showing the process of transcription and translation
• Underneath the picture, write a one paragraph summary of the
lecture notes.