1. CHAPTER 12 DNA (Deoxyribonucleic Acid)

2. BUILDING BLOCKS (MONOMERS)
DNA is made up of repeating units called NUCLEOTIDES.
Each NUCLEOTIDE contains 3 parts
1. SUGAR GROUP—(deoxyribose) always the same
2. PHOSPHATE GROUP- always the same
3. NITROGEN CONTAINING BASE these vary
(Can be ADENINE, GUANINE, CYTOSINE, or THYMINE)

3. DNA Nucleotide O O=P-O N CH2 O C1 C4 C3 C2 Phosphate Group
Nitrogenous base
(A, G, C, or T)
CH2 O C1 C4 C3 C2 5
Sugar
(deoxyribose)

4. MONOMERS becoming POLYMERS
NUCLEOTIDES form long chains by the phosphate group of one nucleotide forming a COVALENT BOND with the SUGAR GROUP of another NUCLEOTIDE (this can occur in any random order of ACTGCTAAATCGC) “Remember that COVALENT BONDS are VERY STRONG “

6. NITROGENOUS BASES
PURINES- nitrogenous bases that have TWO rings of carbon (EXAMPLES- ADENINE and GUANINE)
PYRIMIDINES- nitrogenous bases that have only one ring of carbon (EXAMPLES- THYMINE and CYTOSINE)

7. Nitrogenous Bases A or G T or C PURINES 1. Adenine (A) 2. Guanine (G)
PYRIMIDINES
3. Thymine (T)
4. Cytosine (C)
A or G
T or C

8. Combining strands of DNA
PURINES always form HYDROGEN BONDS with PYRIMIDINES in a specific way
**Remember hydrogen bonds can be easily broken
We call this the “COMPLEMENTARY BASE PAIR RULES”
ADENINE can only bond with THYMINE
GUANINE can only bond with CYTOSINE

9. DNA Double Helix P O 1 2 3 4 5 P O 1 2 3 4 5 G C T A

10. Two strands together form a DNA DOUBLE HELIX shape
Nitrogenous
Base (A,T,G or C)
“Rungs of ladder”
“Legs of ladder”
Phosphate &
Sugar Backbone

11. WATSON and CRICK
The first scientists to identify the shape of DNA as a DOUBLE HELIX.
Won the Nobel Prize in 1962

12. DNA Replication DNA must be copied
The DNA molecule produces 2 IDENTICAL new complementary strands following the rules of base pairing:
A-T, G-C
Each strand of the original DNA serves as a template for the new strand See p. 298

13. DNA Replication DNA must be copied
The DNA molecule produces 2 IDENTICAL new complementary strands following the rules of base pairing:
A-T, G-C
Each strand of the original DNA serves as a template for the new strand See p. 298

14. STEPS IN REPLICATION (pg 188)
TWO DNA STRANDS SEPARATE due to an ENZYME called HELICASES
TWO strands of DNA are used as TEMPLATES for new strands
ENZYMES called DNA POLYMERASE help to “GLUE” the proper nucleotides in place
TWO IDENTICAL DNA STRANDS are formed

15. DNA Replication
DNA Template
New DNA
Parental DNA

16. ASSIGNMENT Draw a strand of DNA—in pen
Draw a second strand of DNA with the proper COMPLIMENTARY BASE PAIRS
SHOW your DNA go thru one round of REPLICATION

17. RNA vs. DNA DNA Double stranded Deoxyribose sugar Bases: C,G A,T RNA
Single stranded
RIBOSE SUGAR
Bases: C,G,A,URACIL
Both contain a sugar, phosphate, and base.

18. Types of RNA (3)
MESSENGER RNA- carries info from the DNA outside the nucleus to the ribosome
TRANSFER RNA- carries amino acids made outside the ribosome
RIBOSOMAL RNA- found attached to the ribosome that helps make proteins

19. Major players in transcription
mRNA- is made during transcription and carries the exact information from the DNA to encode for a specific protien.
mRNA then travels outside the nucleus and attaches to a ribosome

20. TRANSCRIPTION- taking the genetic code in DNA and transferring it into RNA
Process is nearly identical to replication except…….
RNA forms base pairs with DNA
C-G
A-U

21. Steps in Transcription
Step Helicase enzyme splits up (unzips) double stranded DNA
Step 2- DNA is used as a template to make RNA
Step 3- RNA polymerase attaches to specific nucleotides called PROMOTERS and begins to make a long chain Messenger RNA then stops at specific nucleotides called TERMINATION SIGNALS
Step 4- used to make mRNA, tRNA, and rRNA- which will all leave the nucleus

22. TRANSLATION- turning the code of RNA and making it a PROTEIN—PROTEIN SYNTHESIS
2 types of RNA are needed
MESSENGER RNA- long chain that has the proper CODE from the DNA
TRANSFER RNA- that reads the code and attaches the proper amino acid

23. TRANSFER RNA
Chain of RNA that has a specific shape and carries an AMINO ACID to the mRNA

24. CODONS and ANTICODONS
Follow the “rule of threes”- reads 3 nucleotides at a time and has a specific amino acid for that codon
START CODON—AUG
STOP CODON---UGA, UAA, UAG

25. AMINO ACIDS (pg 194)
the monomers for building proteins that are held together by peptide bonds (covalent bonds). There are 20 amino acids that are coded for by one or more codons (64 codons possible)
AUG- the START CODON- codes for the amino acid METHIONINE
UGA, UAA, and UAG- do not code for any amino acids and are considered STOP CODONS

26. RIBOSOMES role in translation
They are the glue that holds the transfer RNA in place at the correct location on the messenger RNA. It then moves along “reading” the mRNA and adding the correct tRNA.
***** More than one RIBOSOME may be “reading” the same mRNA to speed up protein production.

27. ERRORS in DNA, TRANSCRIPTION or TRANSLATION
MUTATIONS- any errors in the DNA or mRNA – this may or may not lead to a major change in the protein made.
POINT MUTATION- a single nucleotide is inserted (paired up) incorrectly
DELETION or INSERTION of a NUCLEOTIDE can lead to a FRAME SHIFT

28. FRAMESHIFT MUTATION
The changing of all the codons due to the addition or subtraction of a nucleotide. Leads to many amino acids being changed.