1. DNA Replication, Transcription, & Translation
Nestor T. Hilvano, M.D., M.P.H.
(Images Copyright Discover Biology, 5th ed., Singh-Cundy and Cain, Textbook, 2012.)

2. Learning Objectives Define key terminologies.
DNA replication, transcription, translation, codon, anticodon, introns, exons, and nucleotide
Compare the structure of DNA and RNA and its functions.
Describe the process of DNA replication.
Describe the locations, reactants, and products of transcription.
Describe the locations, reactants, and products of translation.
Describe major types of mutations and their possible consequences.

3. Wordstem co- together liga- bound or tied pleio- more poly- many
centesis- a puncture

4. DNA Discovery
Rosalind Franklin (1950)- diffracted helical shape of DNA when performing X-ray crystallography using samples of uniformly oriented strands created by Maurice Wilkins
Watson (U.S.) and Crick (Great Britain)- used quantum mechanics and x-ray crystallography (Wilkin and Franklin) to determine DNA structure; double helix model; won the Nobel Prize in medicine
Rosalind Franklin: July 25, 1920 – April 16, 1958

5. Figure 14.3 The DNA Double Helix and Its Building Blocks
A nucleotide consists of three types of chemical groups: a phosphate, a sugar, and a nitrogen-containing base. DNA contains four types of nucleotides, varying only in the type of base found in them. DNA consists of two complementary strands of nucleotides that are twisted into a spiral around an imaginary axis, rather like the winding of a spiral staircase. The two strands are held together by hydrogen bonds between their complementary bases. (Inset) James Watson (left) and Francis Crick, with a model of the DNA double helix.

6. 5 end 3 end P HO A T C G OH 5 4 3 2 1 1 Figure 10.5B
Figure 10.5B The opposite orientations of DNA strands 6

7. DNA Replication Semiconservative; DNA unwound into 2 template strands
New base pairs (complimentary base pairing)
Adding at the end of 3’ end of the template toward the 5’ end (leading strand) or at 5’ end toward the 3’ end (lagging strand= okazaki fragments)
DNA polymerase and DNA ligase

8. Figure 14.5 The Replication of DNA Is Semiconservative
In this overview of DNA replication, the template DNA strands are blue, and the newly synthesized strands are orange. One strand (blue) from the parent double helix is conserved in each newly made daughter double helix (blue and orange).

9. . helicase-unwinds DNA, req. ATP
b. single-stranded binding proteins-keep DNA from rebinding to self
c. origin of replication (1 in proks, multi in euks)
d. primase-synthesiaex RNA primer-short strand-where DNA polymerase attaches to strand
e. DNA polymerase III-open right hand: palm = active site; fingers = recognize bases
f. DNA polymerase I-knocks off RNA/makes DNA (lagging strand)
g. DNA ligase-makes phosphodiester bond-joins sugar phosphate backbone together at gaps (lagging strand)
Build-new DNA built off of template 3` end toward 5` end-only one strand has this orientation = leading strand
other strand = lagging strand= thread thru, add primer and work back toward earlier primer-okazaki fragments

10. Flow of Genetic Information from DNA to RNA to Protein
Organism’s genotype – is carried in its sequence of bases triplet (ex. TAC)
Transcription is= DNA to mRNA
Translation is = mRNA to protein (polypeptide)
Codon – triplets of bases found in mRNA (ex. AUG), which determines A.A. sequence on a polypeptide, 64 possible codons
- 61 code for amino acids
- start codon= AUG (Methionine)
- 3 stop codons = UAG, UGA, UAA

11. Figure 15.5 The 64 Possible Codons Specify Amino Acids or Signals That Start or Stop Translation

12. Figure 15.2 Genetic Information Flows from DNA to RNA to Protein during Transcription and Translation
The transcription of a protein-coding gene produces an mRNA molecule, which is then transported to the cytoplasm, where translation occurs and the protein is made with the help of ribosomes. Different amino acids in the protein being constructed at the ribosome are represented here by different colors and shapes.

13. Transcription What is transcription? RNA polymerase
RNA splicing – introns (nonsense), exons (sense)
Given a DNA template of TACCGC. What is the corresponding codon in mRNA transcribed? _________________
RNA polymerase
DNA of gene
Promoter
DNA
Terminator
Area shown
In Figure 10.9A
Growing
RNA
Completed RNA
polymerase
initiation
elongation
termination
Exon Intron Exon Intron Exon
DNA
Cap
Transcription
Addition of cap and tail
RNA
transcript
with cap
and tail
Introns removed
Tail
Exons spliced together
mRNA
Coding sequence
Nucleus
Cytoplasm

14. DNA Transcription RNA Codon Translation Polypeptide Amino acid A A A C
Figure 10.7_1
DNA A A A C C G G C A A A A
Transcription U U U G G C C G U U U U
RNA
Codon
Translation
Figure 10.7_1 Transcription and translation of codons (partial)
Polypeptide
Amino acid 14

15. Figure 15.3 RNA Polymerase Transcribes DNA-Based Information into RNA-Based Information

16. Translation Ribosome attaches to mRNA
tRNA (anticodon)- interprets the message; delivers amino acids specified by mRNA codons
* 3 stages – initiation, elongation, termination
* Elongation adds amino acids to the polypeptide chain until a stop codon terminates translation
Met
Initiator tRNA 1 2
mRNA
Small ribosomal subunit
Start codon
Large ribosomal subunit
A site U A C
A U G
P site
Figure 10.13B

17. Figure 15.7 Transfer RNA Delivers Amino Acids Specified by mRNA Codons
A space-filling-model (left) and a diagrammatic version (right) illustrate the general structure of all tRNA molecules. Similar regions in the space-filling model and on the diagram are shown in matching colors. Each tRNA carries a specific amino acid (serine in this example) and has a specific anticodon sequence (UCG in this example) that binds to a complementary three-base sequence (the codon) in the mRNA.

18. *anti-codon end- pairs with codon on mRNA *amino acid on 3` end
Fig 3
tRNA:
*anti-codon end- pairs
with codon on mRNA
*amino acid on 3` end
* clover leaf shape base pairs
Amino acid
attachment site 5
Hydrogen
bonds
Anticodon
(a) Two-dimensional structure 5
Amino acid
attachment site 3
Figure The structure of transfer RNA (tRNA)
Hydrogen
bonds 3 5
Anticodon
Anticodon
(c) Symbol used
in this book
(b) Three-dimensional structure

19. (b) Schematic model showing binding sites
Fig b
P site (Peptidyl-tRNA
binding site)
A site (Aminoacyl-
tRNA binding site)
E site
(Exit site) E P A
Large
subunit
mRNA
binding site
Small
subunit
(b) Schematic model showing binding sites
Growing polypeptide
Amino end
Next amino acid
to be added to
polypeptide chain
Figure The anatomy of a functioning ribosome E
tRNA
mRNA 3
Codons 5
(c) Schematic model with mRNA and tRNA

20. Figure 15.8 (Part 1) In Translation, Information Coded in mRNA Directs the Synthesis of a Protein That Has a Particular Amino Acid Sequence

21. Figure 15.8 (Part 2) In Translation, Information Coded in mRNA Directs the Synthesis of a Protein That Has a Particular Amino Acid Sequence

22. Figure 15.8 (Part 4) In Translation, Information Coded in mRNA Directs the Synthesis of a Protein That Has a Particular Amino Acid Sequence

23. http://www. youtube. com/watch
(go to 4:36)
Figure 15.8 (Part 5) In Translation, Information Coded in mRNA Directs the Synthesis of a Protein That Has a Particular Amino Acid Sequence

24. Mutation
Change in the nucleotide sequence of DNA; somatic (body cells; passed on during cell division); germ-line (during gametes development; passed on to offspring)
Caused by errors in DNA replication or recombination, or by mutagens
Point mutation- changes in one base pair of genes (1 gene); substitution, insertion, or deletion
Chromosomal mutation- entire section of chromosome, affects multiple genes; caused by free radicals breaking sugar-phosphate bonds, UC radiation, and chemical affecting structure of bases. C T A
Normal hemoglobin
Mutant hemoglobin DNA G U
Sickle-cell hemoglobin
Normal hemoglobin DNA
Glu
Val
mRNA
Figure 10.16A

25. Point Mutation Can results to:
silent- no change/effect due to redundancy
Mis-sense- change of one A.A. (different A.A. sequence); low efficiency
Non-sense- lead to change one A.A. to stop codon; polypeptide synthesis stop, non-functional protein
Frameshift (insertion or deletion)- entire 3 base codon affected; major difference causing non-functional proteins

26. Figure 15.9 A Change in the DNA Sequence Translates into a Change in the Amino Acid Sequence of the Protein
Two kinds of mutations are shown here: a substitution and an insertion. In each case, the mutation and its effects on transcription and translation are shown in red.

27. Figure 15.10 Mutations in a Single Base in the Hemoglobin Gene Can Lead to Sickle-Cell Anemia

28. Nucleotide substitution
Figure 10.16B
Normal gene A U G A A G U U U G G C G C A
mRNA Protein
Met
Lys
Phe
Gly
Ala
Nucleotide substitution A U G A A G U U U A G C G C A
Met
Lys
Phe
Ser
Ala U
Deleted
Nucleotide deletion A U G A A G U U G G C G C A U
Figure 10.16B Types of mutations and their effects
Met
Lys
Leu
Ala
His
Inserted
Nucleotide insertion A U G A A G U U G U G G C G C
Met
Lys
Leu
Ala
His 28

29. Homework
Define terms: nucleotide, translation, transcription, DNA replication, introns, exons, codons, anticodons, mutation, point mutation, chromosomal mutation.
Describe the 3 types of RNA: mRNA, tRNA, and rRNA.
Give the bases of CATAAG DNA template, what is the corresponding bases in DNA replication?
Given the above DNA template in #3 question, what is the corresponding codons (mRNA) in transcription?
Given AGG codon (mRNA), what is the corresponding anti-codon (tRNA) in translation?
Describe types of point mutation.