1. DNA (Deoxyribonucleic Acid)

2. (a library of about 1,000 books)
AMAZING DNA FACTS…
DNA from a single human cell extends in a single thread for almost 2 meters long!!!
It contains information equal to some 600,000 printed pages of 500 words each!!!
(a library of about 1,000 books)

3. WARM-UP #7

4. Genetic material of cells…
DNA is a NUCLEIC ACID
DNA is made up of repeating monomers called NUCLEOTIDES
GENES – units of genetic material that CODES FOR A SPECIFIC TRAIT
DNA controlls cell function by serving as a template for PROTEIN structure.

5. DNA Nucleotide O O=P-O Phosphate Group Nitrogenous base
(A, G, C, or T)
Sugar
(deoxyribose)

6. A HISTORY OF DNA Discovery of the DNA double helix
A. Frederick Griffith – Discovers that a factor in diseased bacteria can transform harmless bacteria into deadly bacteria (1928)
B. Rosalind Franklin - X-ray photo of DNA.
(1952)
C. Watson and Crick - described the DNA molecule from Franklin’s X-ray.
(1953)

7. Watson & Crick proposed…
DNA had specific pairing between the nitrogen bases:
ADENINE – THYMINE
CYTOSINE - GUANINE
DNA was made of 2 long strands of nucleotides arranged in a specific way
called the “Complementary Rule”

8. DNA Double Helix “Rungs of ladder” Nitrogenous Base (A,T,G or C)
“Legs of ladder”
Phosphate &
Sugar Backbone

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

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

12. Chargaff’s Rule Adenine must pair with Thymine
Guanine must pair with Cytosine
Their amounts in a given DNA molecule will be about the same. T A G C

13. BASE-PAIRINGS C G
H-bonds T A

14. See p. 297
DNA is wrapped tightly around histones and coiled tightly to form chromosomes

15. DNA Replication A-T, G-C DNA must be copied
The DNA molecule produces 2 IDENTICAL new complementary strands following the rules of base pairing:
A-T, G-C

16. DNA Replication Semiconservative Model: .
1. Watson and Crick showed: the two strands of the parental molecule separate, and each functions as a template for synthesis of a new complementary strand. .
DNA Template
New DNA
Parental DNA

17. The Code of Life… A T C G T A T G C G G…
The “code” of the chromosome is the SPECIFIC ORDER that bases occur.
A T C G T A T G C G G…

18. (1961) Watson & Crick proposed…
…DNA controlled cell function by serving as a template for PROTEIN structure.
3 Nucleotides = a triplet or CODON
(which code for a specific AMINO ACID)
AMINO ACIDS are the building blocks of proteins.

19. RNA
RNA is a nucleic acid that reads the DNA sequence and translates it to amino acids, which build proteins
mRNA “reads” – transcription
tRNA “builds” – translation

20. DNA Transcription
DNA can “unzip” itself and mNRA nucleotides match up to the DNA strand.
In an mRNA molecule, the base thymine is replaced by a new base called Uracil (U)

21. C=G A=U DNA Transcription The base pair rule for RNA transcription is:
T is simply replaced by U

22. DNA Translation
The cell uses information from transcripted mRNA to produce proteins
tRNA complements the mRNA using the base pair rule (C=G, A=U)

23. DNA Translation
tRNA then groups the sequence into triplets called codons
Codons code for amino acids, which are monomers that make proteins

24. Amino Acids and Proteins
There are 20 amino acids
Different nucleotide sequences code for different amino acids
The sequence of amino acids determine which kind of protein is produced

26. Genetic Diversity…
Different arrangements of NUCLEOTIDES in a nucleic acid (DNA) provides the key to DIVERSITY among living organisms.

27. Transcription/Translation Quiz
Why is transcription necessary?
Describe transcription.
Why is translation necessary?
Describe translation.
What are the main differences between DNA and RNA.
Using the chart on page 303, identify the amino acids coded for by these codons:
UGGCAGUGC

28. 1. Why is transcription necessary?
Transcription makes messenger RNA (MRNA) to carry the code for proteins out of the nucleus to the ribosomes in the cytoplasm.
2. Describe transcription.
RNA polymerase binds to DNA, separates the strands, then uses one strand as a template to assemble MRNA.
3. Why is translation necessary?
Translation assures that the right amino acids are joined together by peptides to form the correct protein.

29. 4. Describe translation.
The cell uses information from MRNA to produce proteins.
5. What are the main differences between DNA and RNA.
DNA has deoxyribose, RNA has ribose; DNA has 2 strands, RNA has one strand; DNA has thymine, RNA has uracil.
Using the chart on page 303, identify the amino acids coded for by these codons: UGGCAGUGC
tryptophan-glutamine-cysteine

30. LET’S REVIEW DNA… LM p.44
List the conclusions Griffith & Avery, Hershey & Chase drew from their experiments.
Summarize the relationship between genes & DNA.
Describe the overall structure of the DNA molecule.
What are the 4 kinds of bases?