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Chapter 12 DNA and RNA. What is DNA?. DNA (De-oxy-ribo-nucleic Acid) is the nucleic acid that stores the genetic code. What is a Genetic Code? Genetic Codes are programs of the cell. In other words how cells store information they pass from one generation to the next. - PowerPoint PPT Presentation
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What is DNA?
• DNA (De-oxy-ribo-nucleic Acid) is the nucleic acid that stores the genetic code.
What is a Genetic Code?
• Genetic Codes are programs of the cell. In other words how cells store information they pass from one generation to the next.
WHAT IS DNA MADE OF?
• DNA is a polymer (Large Molecule) formed from units called nucleotides.
– A nucleotide is made up of three parts:1. Nitrogen base
2. Deoxyribose (5 carbon sugar)
3. Phosphate group
NITROGEN BASES• There are 4 different nitrogen bases:
• Adenine (A) and Guanine (G) which are the purines
• Cytosine (C) and Thymine (T) which are the pyrimidines
BASE PAIRING RULES
• Erwin Chargaff discovered the base pair ruling that in DNA:
– Adenine (A) pairs with Thymine (T) by 2 hydrogen bonds– Cytosine (C) pairs with Guanine (G) by 3 hydrogen bonds
REMEMBER
• AT and GC – OR ELSE!!!!!
Testing Your SkillCan you write the corresponding Nitrogen Base?
1. GAC TAT ATT GAC ATT GAG CCC TTA
2. ATA GAG CAC GCA TAT CCG AGT TAT
Do you understand how to match up the bases??? IF NOT ASK FOR HELP NOW!!!
STRUCTURE OF DNA:
• Is called a double helix (resembles a twisted ladder): has 2 strands
Watson and Crick
• Made the first model of the DNA ladder called the Double Helix in 1953.
• They used X-ray crystalography pictures created by Rosalind Franklin and Chargaff’s rule to develop their ladder.
• They won the nobel prize in 1962 for their accomplishments.
ROSALIND FRANKLIN
• Rosalind Franklin also played a major role in the ladder’s discovery because Watson and Crick used her photos of the DNA ladder to figure out and assemble the model. (Unfortunately she died 4 years before the nobel prize was awarded at the age of 37 of ovarian cancer. Her contributions were made known later after the award was given. According to Nobel Prize Rules, the individual must be alive in order to receive the award )
History of DNA (CONT)
1.Fredrick Griffith (microbiology research with nucleic acids)
2.Oswald Avery (colleague that completed/supported Griffith’s work)
3.Alfred Hershey and Martha Chase (proved that DNA and not protein is the genetic material of life)
4.Erwin Chargaff (A-T, G-C)5.Rosalind Franklin (x-ray pics-DNA)6.Francis Crick and James Watson (double
helix model)
Born: London, England, July 25, 1920
Died: London, England, April 16, 1958
Pioneer Molecular Biologist There is probably no other woman scientist with as much controversy surrounding her life and work as Rosalind Franklin. Franklin was
responsible for much of the research and discovery work that led to the understanding of the structure of
deoxyribonucleic acid, DNA.
DNA Replication (synthesis)
DNA replication is an important process because as cell divide, it is critical that the two daughter cell are identical to the original cell.
Now we will look at how DNA replication take place.
Process of DNA Replication
1. Each strand (side) of DNA serves as a template for a new strand of DNA
2. Steps of replication:
a) Enzymes unzip DNA breaking hydrogen bonds between bases.
b) The two strands unwind.
c) Each DNA strand serves as a template for complementary bases.
Example: TEMPLATE DNA: TAC-GTT
NEW DNA: ATG-CAA
d) DNA replicates itself exactly so that each new cell will have an identical copy of the original DNA ladder.
DNA REPLICATION VIDEO
REPLICATION VIDEO (ADVANCED)
RNAThere are 3 different types:
1.mRNA
2.tRNA
3.rRNA
mRNA• mRNA is the nucleic acid that
acts as a messenger between DNA and ribosomes and carries the genetic code for making protein from amino acids.
mRNA
Just like DNA, RNA is made of Nucleotides: A, U, C, G.
Notice, RNA does not contain thyamine (T) as a base, but instead has uracil (U).
So in RNA its AU and CG
PROTEIN SYNTHESIS
Why make protein?
Proteins are needed for cell structure and movement, makes enzymes and nucleotides.
TRANSCRIPTION• Transcription is the process
in which a molecule of DNA is copied into a complementary strand of RNA.– DNA is in the nucleus and can’t
leave, so a messenger RNA-(mRNA) must bring the genetic information from the nucleus to the ribosomes in the cytoplasm
Steps in Transcription
1. RNA polymerase attaches to DNA and moves along it unwinding the two strands
2. RNA nucleotides match up with the bases of DNA
Ex: DNA TGCACGCA
mRNAACGUGCGU
CODONS• Codon- is a 3 letter word composed of 3
nucleotides on mRNA.– Each codon codes for a particular amino acid while
chains of amino acids form proteins.– There are 64 different codons; there can be more
than 1 codon for each amino acid.– There are start and stop codons.
EXAMPLES OF CODONS
AUG-CCC-GAA-GGG-UAA
CAN YOU IDENTIFY THE CODONS IN THE PROBLEMS
BELOW?
1. AUGCCCAUAGACUAG
2. AUGGACCGGCUUUAA
YOUR TEACHER WILL TEACH YOU HOW TO USE THE CODON TO IDENTIFY THE AMINO ACID
PROTEIN SYNTHESIS VIDEO
STILL CONFUSED?
• Imagine that you are a mechanic. The repair manual that you use is the DNA ladder.
• If you wanted to copy the instructions to install a radio in your car, would you copy the entire repair manual? (RAISE YOUR HAND TO ANSWER)
• NO!!! You would only copy the portion pertaining to installing the radio. That is what transcription does.
CONTINUED• Enzymes open the DNA ladder and the needed
portion is copied in the form of mRNA.
• Why is it called mRNA? It carries the message or instructions on how to assemble something.
• What’s next? This message is carried from the nucleus to a ribosome which is located outside of the nucleus.
(HINT: M=Messenger)
translation
• is the process of building a protein molecule according to code in mRNA.
Translation cont.
A. During the process, transfer RNA (tRNA) carries amino acids to ribosomes where the amino acids are joined to form the protein. (**ribosomes are the place where protein are made)
Translations cont.
B. Steps of translation:
1. tRNA bind to the mRNA.
2. a “start” codon start the protein synthesis.
3. tRNA contains 3 complementary nucleotides to the mRNA called the anticodon; once it matches it leaves behind amino acid and next codon is read.
Translation cont.
4. More tRNA molecules will come together to create the _____________.
5. Once a “stop” codon is read, the new polypeptide chain is released as a new protein.
Translation Video
