1. Inheritance and the Structure of DNA

2. Deoxyribonucleic Acid

3. DNA Discovery Timeline
1928-Frederick Griffith
transforming factor (material carrying genetic info)
1944-James Watson and Francis Crick
discovered that DNA was the transforming factor 
1952-Rosalind Franklin and Maurice Wilkins
took x-ray photographs of the DNA molecule
1953-Watson and Crick
created a three-dimensional 3-D model of DNA 
1962-Watson, Crick, and Wilkins
received the Nobel Prize in Medicine

4. What is DNA? Genetic material used to express traits Nucleotide units
Deoxyribose (sugar)
Phosphate
Base
Purines (double ring)
Thymine ( T )
Cytosine ( C )
Pyrimidine (one ring)
Adenine ( A )
Guanine ( G )

5. Complementary Strands
Order of bases on the nucleotides in one strand of DNA complements the order of bases on the opposite strand
Anti - parallel
5’ -> 3’
Refers to where sugar & phosphate attach
Direction which new DNA is made
Sugar and phosphate alternate
Make up the sides
base sequence (ATGC)
attach to sugar

6. DNA Replication/Synthesis pg200
DNA stores and transmit information
tells cells which proteins to make and when to make them
DNA located in the nucleus and cannot leave.
Replication is duplication or making more of DNA
Occurs during S phase of interphase
2 main enzymes involved DNA Helicase and DNA Polymerase

8. DNA Helicase and DNA Polymerase
Helicase unzips the DNA by breaking the hydrogen bonds between the two strands
Binding proteins stabilize the strands keeping them open
Nucleotide units are added from a 3’->5’direction(5’->3’ new complementary strand direction), this leading edge is continuous

9. 4. On the other strand of DNA, the 2nd strand called the lagging strand)
nucleotides are added from the 5’ end; creating a complementary strand of 3’->5’sporadically
since polymerase moves in a 5’->3’ it will move around to find location on the original strand that it can match up with to create segments on the new complementary DNA
this leaves gaps (called Okazaki fragments) that are later filled by the enzyme ligase
5. DNA Polymerase proof reads each strand sealing the molecules

10. RNA (Ribonucleic Acid)
RNA differs from DNA
Sugar is ribose
The nitrogen base THYMINE is replaced by URACIL
RNA U bonds with DNA A
RNA is single-stranded
There are three types of RNA
Messenger RNA (mRNA)
Transfer RNA (tRNA)
Ribosomal RNA (rRNA)

11. RNA (created from DNA) Messenger RNA (mRNA) Transfer RNA (tRNA)
copies the information from the DNA in the nucleus
Transfer RNA (tRNA)
reads the information from mRNA
carries amino acids to the ribosome
Ribosomal RNA (rRNA)
Links up with mRNA to read the “message” from DNA and to reveal codons for tRNA

12. Transcription vs Translation pg 206
DNA information to mRNA, tRNA, rRNA
Occurs in nucleus
Translation
mRNA to tRNA and rRNA
Polypeptide bonds are created between amino acids
Twist and turn of these chains create specific proteins
Result in phenotypes of organisms
in cytoplasm

13. Transcription pg 206 Reading the gene RNA polymerase
occurs on only one strand of DNA
RNA polymerase
Transcribed information has created a complementary strand of mRNA from DNA
A=U, C=G

14. Transcription illustration

15. Transcription RNA polymerase, binds to the promotor
Promoter is particular sequence of DNA that RNA polymerase binds
DNA molecule unwinds and strands separate
RNA polymerase adds free nucleotides on one of the DNA strands
Complementary bases (AUGC)
As polymerase moves over DNA the strands rewind
RNA polymerase reaches termination signal indicated by sequence of bases
Releases DNA and RNA (mRNA,tRNA,rRNA)

16. Transcription

17. Genetic Code pg 207 Gene Expression
Amino acids are created from instructions found in the nucleotide sequence on mRNA
Genetic Code term used to describe how the sequence of nucleotide units (bases) corresponds to a particular amino acid
Three letter (bases) word is referred to as a codon
mRNA has the codon

18. Codons in mRNA
Each sequence of 3 bases on mRNA encodes for either an amino acid or stop/start signal
Some amino acids will have 1,2,or 3 different codons
No codon codes for more than one amino acid
64 mRNA codons
There are special codons that act as start and stop to the sequence
For example, AUG acts as a start codon codes for the amino acid Methionine
Others like (UAA, UAG, or UGA) are stop codons that don’t code for amino acids but are the end of the translating sequence
Reading the mRNA table pg 207, let’s try a few

19. Translation
RNA molecules (tRNA, rRNA, and mRNA) take information from DNA to proteins
Translates the sequence of bases found in the gene into material that the body can “read” (visible traits)
Occurs in Cytoplasm

20. RNA molecules

21. How it comes together in cytoplasm

22. Translation pg207 Revisit Protein structure pg 208 Polypeptides
20 different types amino acids
Twist and fold into 3-D structure
Shape critical for function

23. Steps of Translation rRNA, mRNA, and tRNA join together
Enzyme attaches amino acid to one end of tRNA
Other end of tRNA (anticodon) attaches to complementary bases on mRNA
AUG (methionine) begins the sequence
mRNA continues to “read” mRNA codons
tRNA brings the appropriate amino acids
Starting from the 1st codon, tRNA brings in the start amino acid (methionine)
Then as the 2nd tRNA attaches it’s amino acid to the 1st amino acid (creating a peptide bond) the 1st tRNA leaves
This process continues until the stop codon is reached

24. Initiation and Elongation
Textbook pg 208
Initiation and Elongation

25. rRNA reaches the stop codon (UAA, UAG, or UGA)
Polypeptide chain continues to grow as the rRNA “reads” the codons on mRNA
rRNA reaches the stop codon (UAA, UAG, or UGA)
New polypeptide chain is released
The components of translation come apart

26. Elongation, Termination, Disassembly

27. Another view of Protein Synthesis

28. FYI - Deoxyribose vs Ribose sugars
2-Deoxy-Ribose in DNA is replaced by Ribose in RNA.
The difference is a hydroxy group ( -OH ) in RNA versus a single proton ( -H ) in DNA.
The extra -O- in the ribose backbone prevents formation of stable double-helices in RNA.