1. DNA
The Code of Life

2. Topics Covered The DNA Molecule DNA Replication How DNA works
Transcription
Translation

3. DNA Deoxyribonucleic acid Discovered by Watson and Crick
Made up of nucleotides
Double helix
2 coiled strands (twisted ladder)
Strands are complimentary

4. Nucleotide NB S P THREE PARTS Sugar Phosphate group Nitrogen Base
Deoxyribose (in DNA)
Ribose (in RNA)
Phosphate group
Nitrogen Base NB S P

5. The Four Nucleotides PURINES Guanine (G) Adenine (A) PYRIMIDINES
Cytosine (C) T
Thymine (T)

6. Two Complimentary Strands
BASE PAIRING
(Chargaff’s Rule)
A – T or T – A
G – C or C - G C G A T G C T A

7. The Double Helix

8. DNA Replication Why does DNA need to replicate (copy) itself?
MITOSIS
Replication preserves the sequence of bases in an organism’s DNA

9. DNA Replication: Step 1 T A C G T A C G
The DNA molecule unzips

10. Replication: Steps 2 & 3
DNA polymerase adds the correct complimentary nucleotide to each exposed strand
A complimentary strand is created for each original strand T A C G A T T A G C C G T A

11. DNA, Genes & Chromosomes
long strands of DNA
How many chromosomes do humans have?
Genes
part of a chromosome
Each gene codes for a different protein

12. Proteins Gene Expression Amino Acids
The use of genetic material to make a protein
Protein ultimately determines a trait
Amino Acids
Building blocks of proteins

13. How does DNA code for a protein?
Nucleotide bases “spell out” the message
ORDER is important
OIGLOBY
BIOLOGY
DNA alphabet has 4 letter
G A T C

14. Protein Synthesis Transcription An RNA copy of DNA is made Translation
RNA is translated in to a protein
RNA
transcription
Protein
translation
DNA

15. RNA Ribonucleic acid Messenger for DNA Single stranded
No thymine (T) has uracil (U) instead A G U

16. Transcription An RNA copy of DNA is made Occurs in the Nucleus
Called mRNA
Only one side of DNA is copied
Occurs in the Nucleus
Once mRNA is made it leaves the nucleus (through a pore)

17. TRC: Step 1 T A C G T A C G
The DNA molecule unzips

18. TRC: Step 2
RNA polymerase binds to one strand of DNA at the promoter site T A C G

19. TRC: Step 3
RNA pol. Pairs each nucleotide base with its complimentary base
One strand Only!! T A C G A U G C U A

20. TRC: Step 4
New messenger RNA (mRNA) leaves the nucleus through a nuclear pore
nucleus
cytoplasm
A U G C U A A U U

21. Translation RNA translated into a protein
Two types of RNA work together
mRNA – messenger
tRNA – transfer
Occurs in the cytoplasm
Genetic Code is the translator
Each “word” is 3 letters
GCA = alanine (see genetic code)

22. Genetic Code CODON ANTICODON three letter “word” in mRNA
Specify a particular amino acid
ANTICODON
Three leter “word” in tRNA
Complimentary to the codon

23. The Genetic Code

24. TRL: Step 1 mRNA “start” codon binds to a ribosome AUG = start
AUG = methionine
ribosome
A U G C U A A U U

25. TRL: Steps 2 & 3
tRNA picks up an amino acid in the cytoplasm and carries to ribosome
tRNA anticodon binds to complimentary mRNA codon
A U G C U A A U U
U A C
met
U A C
met

26. TRL: Steps 4 & 5
Amino acid detaches from the tRNA and attaches to a growing protein chain
tRNA leaves to find another amino acid
A U G C U A A U U
U A C
met
U A C
met

27. TRL: Step 6
Continues as mRNA passes through ribosome and one tRNA after another is selected to match the mRNA codons
G A U
leu
met
A U G C U A A U U
met
G A U
leu
A U G C U A A U U
met
G A U
leu
G A U
leu

28. TRL: Step 7
Ends when a “stop” codon is reached and the newly assembled protein is released into the cell
leu
met
A U G C U A A U U
stop

29. G G C C T A A C G A T T