DNA Transcription and Translation! How cells “read” the DNA and use those instructions to make Proteins!

RNA RNA stands for Ribonucleic Acid RNA is very similar to DNA except… 3 differences between RNA and DNA is: RNA’s shape is a single strand! It has a backbone made of phosphate molecules and ribose sugars The four bases are Cytosine, Guanine, Adenine, and Uracil (takes the place of Thymine)

Three Types of RNA Messenger RNA (mRNA) Transfer RNA (tRNA) Ribosomal RNA (rRNA) *not pictured

Replication vs. Transcription DNA Replication is the process where a DNA makes a copy of itself before cell division Transcription is where only a small piece of DNA is transcribed (re-written) as a single strand of mRNA A transcript is a “written message” Helicase enzyme breaks the hydrogen bonds between the base pairs of DNA apart. RNA polymerase builds the new strand of mRNA Strand of mRNA

DNA Replication- when DNA splits and both sides are used to make 2 identical copies of DNA! Transcription- where a small section of DNA is used to form mRNA prior to protein synthesis! mRNA

Why Transcription? DNA cannot leave the nucleus… EVER (too big!) However, proteins are made by the ribosomes inside of cells, not the nucleus! To get the DNA instructions to the ribosomes, the message is sent out on a piece of mRNA (through the nuclear pores!) Once the ribosomes get the mRNA, they can translate the message and build the proteins! 5’ UAU CGC UAG CAU GAG CUC GCC AAA GAU 3’

Making an mRNA A lot like replication, only you use U’s rather than T’s! 5’ TAA CGG TAT CAG 3’-DNA original 3’ AUU GCC AUA GUC 5’ –mRNA copy 5’ TAC CAT GAC ATT 3’-DNA original 3’ AUG GUA CUG UAA5’ –mRNA copy

Translation “Translate” means to decode During translation, the instructions in mRNA are decoded to build a protein This happens one amino acid at a time (Remember- amino acids are the building blocks of proteins!) Ex: “CGC” codes for the amino acid “Arginine”

Here is the Codon Table

Step One-Translation First, the mRNA threads itself into the grooves of the ribosome (the protein makers) Every three bases is called a codon, which translates into one amino acid. Ex: “CGC” codes for the amino acid “Arginine” codons

Step Two-Translation A tRNA carries the amino acid “Arginine” over to the ribosome The ribosome recognizes the tRNA because of a complimentary anti-codon on the bottom (looks like a little 3 prong plug!) The ribosome attaches amino acids to the rest of the protein chain until it gets to a STOP codon (ex: UAA, UAG, etc)

Translation “Big Picture”

Protein Synthesis Synthesis (or synthesize) means “to make or build something” The process where amino acids are linked together to make protein chains is called protein synthesis. Ribosomes synthesize these proteins based on base pairs of the mRNA There are 20 Amino Acids in all!

This portion of DNA translates into what amino acid sequence? DNA original- 5’ TAC CGG TGA CAT GAC 3’ mRNA- 3’ AUG GCC ACU GUA CUG 5’ Amino Acids- methionine, alanine, threonine, valine, leucine

Amino Acid Translation Chart!