Protein Synthesis and Gene Expression

zDNA: deoxyribonucleic acid--contains sugar deoxyribose. zDNA is double stranded. zDNA contains bases adenine, thymine, guanine, cytosine. zDNA never leaves the nucleus. zRNA: ribonucleic acid-- contains sugar ribose. zRNA is SINGLE stranded. zRNA contains bases adenine, guanine, cytosine and URACIL. zRNA can leave the nucleus. Lets Review DNA & RNA

Remember there are three types of RNA zmRNA: messenger RNA mRNA tRNA towing Amino acid zrRNA: ribosomal RNA ztRNA: transfer RNA.

Overall process of protein synthesis transcriptiontranslation DNA RNAProtein

TRANSCRIPTION Takes place in the nucleus translation Moves out of nucleus into the cytoplasm & attach to ribosome

DNAs tragedy zDNA contains volumes of information about making protein. zUnfortunately, DNA is too huge to leave the nucleus. If I could only get out there… Id show them a thing or two! ribosomes nucleus

How does the cell solve this problem….transcription zThats where mRNA comes in. zmRNA helps get DNAs message out to the ribosomes... How do I tell those guys what I want them to do? I can help!

First, DNA unzips itself... zDNA unzips itself, exposing free nitrogen bases.

First, DNA unzips itself... zDNA unzips itself, exposing free nitrogen bases.

First, DNA unzips itself... zDNA unzips itself, exposing free nitrogen bases.

First, DNA unzips itself... zDNA unzips itself, exposing free nitrogen bases.

First, DNA unzips itself... zDNA unzips itself, exposing free nitrogen bases.

Next, mRNA is made... zmRNA is made from the DNA template zmRNA matches with free DNA nitrogen bases in a complimentary fashion

Next, mRNA is made... zmRNA is made from the DNA template zmRNA matches with free DNA nitrogen bases in a complimentary fashion

Next, mRNA is made... zmRNA is made from the DNA template zmRNA matches with free DNA nitrogen bases in a complimentary fashion

Next, mRNA is made... zmRNA is made from the DNA template zmRNA matches with free DNA nitrogen bases in a complimentary fashion

Next, mRNA is made... zmRNA is made from the DNA template zmRNA matches with free DNA nitrogen bases in a complimentary fashion

Next, mRNA is made... zmRNA is made from the DNA template zmRNA matches with free DNA nitrogen bases in a complimentary fashion

Next, mRNA is made... zmRNA is made from the DNA template zmRNA matches with free DNA nitrogen bases in a complimentary fashion

Next, mRNA is made... zmRNA is made from the DNA template zmRNA matches with free DNA nitrogen bases in a complimentary fashion

Next, mRNA is made... zmRNA is made from the DNA template zmRNA matches with free DNA nitrogen bases in a complimentary fashion

Next, mRNA is made... zmRNA is made from the DNA template zmRNA matches with free DNA nitrogen bases in a complimentary fashion

Next, mRNA is made... zmRNA is made from the DNA template zmRNA matches with free DNA nitrogen bases in a complimentary fashion

Next, mRNA is made... zmRNA is made from the DNA template zmRNA matches with free DNA nitrogen bases in a complimentary fashion

Next, mRNA is made... zmRNA is made from the DNA template zmRNA matches with free DNA nitrogen bases in a complimentary fashion

Next, mRNA is made... zmRNA is made from the DNA template zmRNA matches with free DNA nitrogen bases in a complimentary fashion

Next, mRNA is made... zmRNA is made from the DNA template zmRNA matches with free DNA nitrogen bases in a complimentary fashion

Next, mRNA is made... zmRNA is made from the DNA template zmRNA matches with free DNA nitrogen bases in a complimentary fashion

Next, mRNA is made... zmRNA is made from the DNA template zmRNA matches with free DNA nitrogen bases in a complimentary fashion

Next, mRNA is made... zmRNA is made from the DNA template zmRNA matches with free DNA nitrogen bases in a complimentary fashion

mRNA leaves the nucleus... zDNAs code is copied to mRNA in three letter groups called codons. After mRNA is made from the DNA template, it is ready to leave the nucleus. I hope he can tell them what to do!

The next step...Translation mRNA meets the Ribosomes! (No, its not a new sitcom on Fox…)

mRNA tries to talk to the ribosomes… zmRNA leaves the nucleus and travels to the cytoplasm, where the ribosomes are located. I have a message for you! Its from DNA! What does he want now? Its always something! Once there, mRNA meets up with the ribosomes

mRNA tries to talk to the ribosomes…but is unsuccessful. zHowever, the ribosomes cannot understand the message mRNA is carrying. Why dont they get Why cant we tell what hes saying? We need a translator!

tRNA Saves the Day! Now the cell can make a protein! The boss will NOT be happy about this... We wont work until we know what to do! Where is that translator? Looks like trouble for this cell… Id better help! Tyrosine

tRNA: Transfer RNA Tyrosine zChemically, tRNA is clover-leaf shaped. zAt one end, it carries an amino acid. zAt the other end, it has a three letter code known as an anticodon.

Anticodon? Whats that? zThis anticodon is the complement to the codons contained within mRNA. Can you find the mRNA complement to the anticodon on tRNA? Tyrosine

Some notes about Amino Acids zThere are 20 known amino acids present in living things. zHow is it possible to get a group of four letters to code for 20 things? zPut them into groups of three… y4 3 = 64 codes Number of nitrogen bases Number of members in a group of nitrogen bases

Whats a codon, anyway? zHere is what a codon looks like. It is a sequence of 3 bases. zHow we determine what amino acid each codon codes for must be read off of a codon chart. zThis is also known as the genetic code.

Codon chart UCA G U Phenylalanine Leucine Serine Tyrosine Stop Cysteine Stop Tryptophan UCAGUCAG C Leucine Proline Histidine Glutamine Arginine UCAGUCAG A Isoleucine Methionine Threonine Asparagine Lysine Serine Arginine UCAGUCAG G Valine Alanine Aspartic Acid Glutamic Acid Glycine UCAGUCAG First Base Second Base Third Base

The Wonderful World of Amino Acids zIt is possible for some amino acids to have more than one codon. zThere are three stop codons…they are UAA, UGA and UAG. zThere is also one START codon…AUG.

How a Translator works… zFirst, the anticodons on tRNA meet up with the mRNA start codon (AUG) at the ribosome zNext, another tRNA meets up with its corresponding mRNA. zEach tRNA carries an amino acid. Tyrosine

How a Translator works… zOnce two amino acids are made, a bond forms between them zThis process continues until a stop codon on mRNA is reached. Tyrosine