1. Journal 3/7 ATCCGG Don’t forget to write the questions!
No homework!
Don’t forget to write the questions!
Describe the structure of DNA.
Draw the complementary DNA strand:
ATCCGG
Agenda:
Structure of DNA worksheet

2. Journal 3/8 Don’t forget to write the questions!
No homework!
Don’t forget to write the questions!
What two components make up the backbone of DNA?
What are the 4 nitrogenous bases?
Agenda:
Have your DNA and eat it too! lab

3. With 1 partner:
Build your DNA molecule as per the instructions on your handout. 1 model per pair.
Label the sugar phosphate backbone, 1 adenine, thymine, cytosine, and guanine. Use masking tape & toothpicks.
Answer the questions. Everyone fills in their OWN answer sheet.

4. Journal 3/6 Don’t forget to write the questions!
No homework!
Don’t forget to write the questions!
Describe what you know about the structure and function of DNA.
Agenda:
Notes on DNA
Structure of DNA worksheet

5. CHAPTER 10: DNA,RNA & Protein Synthesis

6. So - What is DNA? It’s in the nucleus of most cells in your body.
A DNA molecule is a double strand of nucleotides
The Double Helix shape is formed by base pairs attached to a sugar-phosphate backbone.

7. I. Discovery of DNA 1. Fredrick Griffith 2. Oswald Avery
Many scientists had wrongly believed PROTEINS would be the molecules which contained hereditary information.
Some scientists who did experiments that proved DNA had genetic information:
1. Fredrick Griffith
2. Oswald Avery
3. Hershey & Chase

8. James Watson & Francis Crick
In 1953 DNA structure discovered
Double Helix model.
(2 chains of DNA)
Showed how DNA could replicate.
Relied on work of other scientists:
Rosalind Franklin & Maurice Wilkins took X-ray photos of DNA structure
( BUT- Franklin died 1958 before Watson & Crick received Nobel Prize )

9. II. DNA structure
Double Helix shape is formed by base pairs attached to a sugar-phosphate backbone.
The 4 “ letters” in the genetic code are the 4 nitrogenous bases inside the molecule. (A, T, G, C)

10. B. Parts of Nucleotides 1. 5 carbon sugar in DNA- deoxyribose
(in RNA= ribose)
2. phosphate group
3. nitrogenous bases ( there are 4 different ones)
Adenine
Guanine
Cytosine
Thymine
(in RNA- no thymine- Uracil is the base)

11. C. How Chemical Bonds hold DNA together
Covalent bonds- on the “Backbone” between sugar & phosphates of 2 nucleotides
Hydrogen bonds- zips down the middle- between complementary nitrogenous bases – holds A to T , G to C.

12. Nitrogenous bases Pairing Rules: the letters: A,T,G,C
These 4 letters make up the genetic alphabet
Base Pairing Rules:
Adenine always bonds with Thymine (AT)
Guanine always bonds with Cytosine (GC)

13. Quick write: AAACTGCGTAA
Draw the complementary strand for the following DNA molecule:
AAACTGCGTAA

14. Answer AAACTGCGTAA TTTGACGCATT
Draw the complementary strand for the following DNA molecule:
AAACTGCGTAA
TTTGACGCATT

15. Quick write:
Draw the complementary strand for the following DNA molecule:
CGCGAATA

16. ANSWER CGCGAATA GCGCTTAT
Draw the complementary strand for the following DNA molecule:
CGCGAATA
GCGCTTAT

17. Must have 1 purine (a 2 ring shape) plus 1 pyriomidine (1 ring shape) in each pair or they would not “fit” inside ladder of DNA
Purines (A, G) double C ring
Pyrimidines (T, C) single C ring

18. Quickwrite
How are purines and pyrimidines different?

19. III. DNA Replication
A. Is the process by which DNA is copied in a cell before a cell divides by mitosis, meiosis or binary fission.

20. B. Steps in Replication
1. Separate- Helicase enzymes separate hydrogen bonds in strands & create replication fork
2. Attach- DNA polymerase enzyme -adds nucleotides
3. Release –DNA polymerase enzyme – now have 2 identical DNA strands
oak.cats.ohiou.edu/.../Heredity/Heredity.htm

21. DNA Replication Fork:
DNA synthesis occurs in 2 directions (see blue arrows) from the
5 prime end to the 3prime end on both strands, but in 1 direction overall.
The leading strand is the 5 to 3 end and the lagging strand is put together
with sections called Okazaki fragments.

22. DNA unzips & copies itself
The original DNA is shown all in blue. The red strands in the daughter DNA are the ones which have been built on the original blue strands during the replication process.

23. "semi-conservative replication"
Each of the daughter molecules is made of half of the original DNA plus a new strand.
“Semi-conservative replication" means half of the original DNA is conserved (kept) in each of the daughter molecules.

24. DNA replication practice:
If a DNA strand had the following nucleotide
sequence what would the sequence of the
complementary daughter strand be?
5'-ATGCGGCTAGAATATTCCA-3'
TACGCCGATCTTATAAGGT

25. C. Errors
DNA replication is very accurate.
Errors occur ~ 1 in 1 billion paired nucleotides.
“Proofreading” enzyme checks for “spelling” errors.
*If a mistake does occur- new DNA is different:
Mutation- a change in the nucleotide sequence of a DNA molecule.
Caused by chemicals, radiation,UV rays.
Mutations can be favorable
- or harmful. (examples- sickle cell, cancer)

26. IV Protein Synthesis Flow of Information (DNA to RNA to Proteins)
Before protein can be synthesized, the instructions in DNA must first be copied to another type of nucleic acid called messenger RNA.
Then -a group of 3 nucleic acids codes for an amino acid & it is built at the ribosomal RNA with help from the transfer RNA

27. RNA differs from DNA in the following ways:
RNA is single stranded while DNA is double stranded.
RNA has a sugar called ribose while DNA has a sugar called deoxyribose.
RNA has the nitrogenous base uracil while DNA has the base thymine.

28. B types RNA:
1. messenger RNA(mRNA) – is the “list” of amino acids needed to build the protein
2. transfer RNA (tRNA) – is the “hook” –picks up amino acids needed to build a protein.
3. ribosomal RNA (rRNA) -is the “place” building occurs

29. Messenger RNA, or mRNA. Transfer RNA or tRNA. Ribosomal RNA or rRNA
carries the code for building a protein from the
nucleus to the ribosomes in the cytoplasm. It acts
as a messenger. IT’S THE “LIST”
Transfer RNA or tRNA.
picks up specific amino acids in the cytoplasm &
brings them into position on ribosome where
they are joined together in specific order to
make a specific protein. IT’S THE “HOOK”
Ribosomal RNA or rRNA
place for protein synthesis. IT”S THE “PLACE”

30. C. Steps in Transcription-making RNA
1. Attach enzyme: RNA polymerase (enzyme)– binds to promoter area on DNA
2. Add: Nucleotides added & joined by the enzyme (RNA polymerase)
Stop: Termination signal -stop- RNA polymerase releases both DNA & new RNA molecules

31. Transcription: making RNA from DNA

32. TRANSCRIPTION practice:
Which nitrogen base CAN’T you use during transcription ? _____________
Use the DNA code provided below to copy an m-RNA:
1. ACTGGATAC
________________
2. ACGGATCGTGCCTA
______________________

33. D. Proteins Review of protein structure
-recall that proteins are made of amino acid monomers (building blocks) joined together with peptide bonds
-there are 20 different amino acids, the order they are joined determines the structure & function of the proteins.
-proteins can be very large, complicated molecules

34. mRNA codons for specific amino acids
Each 3 nucleotide sequence (letters) in mRNA encodes for 1 specific amino acid, or a “start” or “stop” signal.
Each 3 nucleotide group is called a codon.
The genetic code- means the rules that relate how a particular sequence of nitrogenous bases corresponds to a particular amino acid. (3 letters = 1 amino acid)

36. teachline.ls.huji.ac.il/72693/weekly2.html

37. E. Steps in Translation (Making Proteins from RNA)
Initiation- tRNA & mRNA join together.
(The codon is on the mRNA, the “anticodon” is on tRNA)
The tRNA has an amino acid attached to it)
Elongation- continued as ribosome moves the distance of 1 codon on mRNA
Protein- is built with new tRNAs attaching each amino acid as it reads the codons on the mRNA.
Termination- ribosome reaches “stop” codon on the mRNA
Disassembly – each piece is free.
(see sequence page in textbook)

38. How a protein is translated:

39. mRNA, tRNA & ribosomal RNA all work together to add amino acids to a polypeptide (a protein)

41. Remember:
Replication- copying DNA from DNA
Transcription- making RNA from DNA
Translation- making proteins