1. Nucleic Acids and Protein Synthesis
Modern Biology – Chapter 10

2. I. Molecular Biology Processes
A. Replication -- copying of DNA
1. Occurs in nucleus
2. Identical DNA strand is made
B. Transcription -- DNA to mRNA
1. (mRNA) copied to move outside
nucleus
C. Translation -- of message into protein
sequence
1. Occurs in the cytoplasm at the
ribosome
2. Amino acids are assembled to
a. Proteins - physical structure
b. enzymes - catalyze other molecules in body

3. Scientists involved with discovering the double helix
Many scientists figured out a piece to the puzzle 1. Most notable: Watson and Crick 2. Also: Rosalind Franklin and Maurice Wilkins

4. DNA – Deoxyribonucleic Acid
Organic molecule that carries the blueprints of living organisms
1. Stores and transmits the genetic information
2. Controls the production of protein
B. Composed of repeating subunits - nucleotides

5. Nucleotides A. Each nucleotide has three parts
1. A five – carbon sugar called deoxyribose
2. A phosphate group (phosphorous
surrounded by oxygen)
3. A nitrogen base (4 kinds)
a. adenine, guanine, thymine, cytosine

6. Nitrogen Bases 4. Purines 5. Pyrimidines a. Adenine and guanine
b. Contain a double ring of carbon and nitrogen
5. Pyrimidines
a. Thymine and cytosine
b. Contain a single ring of carbon and nitrogen

7. DNA Structure

8. DNA Structure DNA is a double helix – like a spiral staircase
Complementary Base Pairing - A weak hydrogen bond holds nitrogen bases together:
Adenine bonds with thymine to form a step
Cytosine bonds with guanine to form a step
Deoxyribose sugar and phosphate are backbone or sides of the ladder – covalently bonded together

9. DNA Replication
Cells that divide must pass exact copies of their DNA to offspring cells
Complementary base pairing allows for complementary nucleotide chains
This led to the discovery of how DNA copies itself
The two nucleotide chains must unwind and each chain serves as a template for a new chain

10. DNA Replication
First Step – the separation of the two nucleotide chains
They separate at a point called the replication fork
The chains are separated by helicase enzymes, which break the hydrogen bonds between the nitrogen bases

12. Replication of DNA
Next Step – the addition of nucleotides to each side of the unwound DNA molecule
DNA polymerase enzymes add nucleotides by covalently bonding a sugar to a phosphate
Each strand reacts with complimentary bases floating in the nucleus
The bases are joined through hydrogen bonding
Copying occurs at many points on DNA

14. Accuracy and Repair of DNA
DNA replication is accurate - usually only 1 error in every 10,000 paired nucleotides
But any error, called a mutation, can have serious effects
Radiation, chemicals , heat can damage DNA (mutation)
Cell has proofreading techniques – like spell check
Over 20 or more repair enzymes fix errors

15. Do Now What is the function of DNA?
What are the 4 nitrogen bases in DNA nucleotides and how do they pair up?
What are the two main enzymes involved in DNA replication?

16. RNA
The DNA that contains the genetic code to make all of your proteins is trapped in the nucleus
The ribosomes, enzymes, and amino acid building blocks of protein are out in the cytoplasm
RNA is responsible for getting the code from the nucleus to the cytoplasm
Copies DNA and then moves outside the nucleus to synthesize proteins

17. RNA – Ribonucleic Acid
Like DNA it is made up of repeating nucleotides Differences between DNA and RNA: RNA single stranded RNA has ribose sugar rather than deoxyribose RNA uses Uracil nitrogen base rather than Thymine to pair with Adenine

18. Types of RNA
A. Messenger RNA B. Transfer RNA C. Ribosomal RNA

19. Messenger RNA (mRNA)
Single uncoiled chain of RNA that transmits DNA’s information from nucleus to cytoplasm

20. Transfer RNA (tRNA) 80 RNA nucleotides folded into a hairpin shape
There are ~ 45
different ones
that bind to
specific amino acids

21. Ribosomal RNA (rRNA)
Consists of RNA nucleotides in globular form – most abundant RNA type
Along with proteins,
rRNA makes up the
ribosomes where
proteins are made

22. Transcription
Process by which genetic information is copied from DNA to mRNA
An enzyme – RNA polymerase – initiates transcription by binding to promoter regions on DNA
As RNA polymerase binds to promoter, the DNA molecule separates
Only one of the DNA strands acts as a template

23. Transcription
RNA polymerase connects RNA bases to the growing RNA strand
The same as when DNA is replicated but uracil is used instead of thymine
It continues until it reaches a termination signal

24. Do Now How is RNA different from DNA? What are the three types of RNA?
What is the purpose of Transcription?

25. Translation - Protein Synthesis
Proteins are polymers of amino acids
There are 20 different amino acids
The sequence of amino acids determines the structure of the protein
The function of the protein depends on its structure

26. Translation - Protein Synthesis
A. The sequence of nucleotides in an mRNA strand is translated into a sequence of amino acids to make a protein
B. A series of three nucleotides on RNA, or codon, codes for one amino acid.
C. There are 64 codons and only 20 amino acids, so several codons can code for the same amino acid
D. There are also a start codon (AUG) and stop codons (UAA, UAG, UGA)

27. Translation - Protein Synthesis
mRNA carrying the genetic code from DNA enters the cytoplasm and meets up with a ribosome
Ribosomes bind to mRNA and tRNA
Amino acids floating in the cytoplasm are brought to the ribosome by tRNA

29. Translation - Protein Synthesis
Each tRNA molecule has a region that bonds to a specific amino acid
Each tRNA also has a sequence of three nucleotides called the anticodon
The anticodon is complementary to and pairs up with a corresponding mRNA codon.

33. Translation
A. mRNA moves out of the nucleus B. mRNA goes to ribosomes and attaches to start codon (AUG) C. tRNA moves amino acids in cytosplam to ribosome D. tRNA anticodon bases pair with codon and drag amino acid to add to polypeptide E. Ribosome enzymes create peptide bonds between amino acids F. Amino acids are added until stop codon is reached