2.  DNA (deoxyribonucleic acid).
 All living things contain DNA.
 Source of genetic traits.
 DNA is a nucleic acid.
 Nucleic acids are made of
nucleotides.

3. Nucleotides
 Made of three
things:
1. Phosphate
(PO4)
2. Sugar
(deoxyribose).
3. Nitrogen base.

4. Nitrogen Bases
Four nitrogen bases
makes four different
nucleotides:
–Guanine
–Cytosine
–Adenine
–Thymine

5. Chargaff’s Rule
 He measured amounts of each
base in various organisms and
found:
amt of adenine (A) = thymine (T)
amt of cytosine (C) = guanine (G)
 This meant that A bonds to T
and C bonds to G
 If 20% of strand is A, what %T?
%C?

6. Structure of DNA
 Discovered by Watson and Crick
 Double helix- “spiral staircase”, 2
strands of nucleotides
 Siderails-sugar and phosphate
 Rungs-nitrogen bases
– A----T
– C----G
Hydrogen bonds (glue)

7. What is DNA Replication?
 Replicate = make “exact” copies.
 All DNA must be replicated before a cell can
divide. Why?
 Why do cells need to divide?
1.Growth.
2.Repair or replace
damaged cells.
3.Regenerate body parts
(not all things can do this).

8. Enzymes and Replication
 Helicase- unwinds DNA
 DNA polymerase-moves along each strand
and brings in bases for new strand copy

9. DNA Replication
 Can be a mistake in replication
 Mutations-change in DNA
 Caused by mutagens, such as X-rays,
toxins, drugs, UV light, etc.
 Can cause disease, such as cancer,
cystic fibrosis, etc.
 Can be:
– insertions of extra bases
– deletions of bases
– substitutions of the wrong bases.

10. Mutations
Substitution

11. How Much DNA Is In Our Cells?
 Chromosome-strands of DNA coiled tightly
 Human cell has 46 (23 pair 2 sets of 23)
 23 from Mom
 23 from Dad

13.  If all body cells contain the same # of
chromosomes, why are all cells so
different?
 Different cells make different proteins.
 Different “active” segments of DNA.
 During early stages of development, cells
become “specialized.”

14.  The first few cells that develop from
the zygote are called stem cells.
 Stem cells differentiate into other
cells.

15. 2 Types of Cells
 Body cells somatic
 diploidchromosomes are in pairs (23 pairs)
 Reproductive cellsgametes
 egg & sperm
 haploid no pairs (23)

16. What is the Purpose of DNA?
 The cell “factory” makes proteins.
 Gene- a segment of DNA that codes for a
protein.
 DNA has 1000’s of genes to make many
different types of proteins.
– Fingernails, hair, enzymes, hemoglobin, etc.
 Protein - polymer of amino acids

17. What is the Purpose of DNA?

18. RNA (Ribonucleic acid)
 _____RNA____vs._____DNA___
single strand double strand
sugar= ribose sugar= deoxyribose
A, C, G, U (uracil) A, C, G, T
mRNA, rRNA, tRNA “DNA is DNA”
all over nucleus only

19. Structure RNA

20. Part 1of Protein Synthesis:
Transcription
 Transcription: DNA  RNA (messenger)
 Occurs in nucleus
 DNA complementary to mRNA
 DNA: ATA-CGG-AAT
transcription in nucleus
mRNA: UAU-GCC-UUA

22. Part 2 of Protein Synthesis:
Translation:
 Translation: mRNA  protein
 Occurs at ribosomes in cytoplasm
 Codon-Three bases on mRNA that code for
an amino acid
 mRNA: UAU-GCC-UUA (3 codons)
translation in cytoplasm
protein: a.a.---a.a---a.a.
 mRNA needs the help of tRNA to bring in
the amino acids

23. Whole Process
DNA: ATA-CGG-AAT
transcription in nucleus
mRNA: UAU-GCC-UUA(3 codons)
translation in cytoplasm
protein: a.a.-a.a-a.a.
How do we know what amino acid results?
The Codon chart or wheel!!!

25. The Codon Wheel