1. DNA, RNA, & Protein Synthesis
Unit4 – Lecture3

2. DNA DNA = De-oxy-ribo-nucleic Acid “blueprint” for traits
double helix shape
composition:
polymer of nucleotide monomers
nucleotide [3 parts]:
sugar [deoxyribose]
phosphate
nitrogen base

3. Nitrogen Bases Nitrogen Bases: are complementary:
adenine [A] bonds with
thymine [T]
cytosine [C] bonds with
guanine [G]

4. Nitrogen Bases – cont’d
amount of A = amount of T
amount of C = amount of G
purines: A & G
pyrimidines: C & T

5. Discuss
With what you just learned, find the answer to the following math problem:
If your cells contained 12% adenine, how much of each of the other nitrogen bases do your cells contain?

6. 76 / 2 = amount of C or amount of G
Discuss
If your cells contained 12% adenine, how much of each of the other nitrogen bases do your cells contain?
if A = 12% then T = 12%
total = 24% A&T
100% - 24% = amount of C&G
76% = amount of C&G
76 / 2 = amount of C or amount of G
C = 38%, G = 38%

7. DNA – cont’d Watson & Crick [1953] proposed the structure of DNA
stole the work of Rosalind Franklin
X-Ray Crystallography

8. DNA Replication
happens in the cell nucleus
occurs during interphase

9. DNA Replication – cont’d
enzyme unzips DNA double strand by breaking the hydrogen bonds between bases
free-floating bases bond to open DNA

10. DNA Replication – cont’d
continues…
end result = 2 strands, ½ new & ½ old DNA
repeat.

11. RNA RNA – Ribo-nucleic Acid sugar = ribose [instead of deoxyribose]
single stranded
has nitrogen base Uracil instead of Thymine
A bonds with U
C bonds with G

12. Discuss
Restate to your partner what the three differences are between RNA and DNA.

13. RNA – cont’d [RNA] three types: mRNA – messenger complementary to DNA
ferries DNA’s message out of the nucleus
contains codons
codon – segment of three bases in mRNA
1 codon = 1 amino acid or “start” or “stop”
20-some of them exist

14. Codon Chart

15. RNA – cont’d [RNA] [three types:] tRNA – transfer
ferries amino acids to ribosome
contains “anticodons”
complementary to mRNA
rRNA – ribosomal
makes up the ribosomes

16. RNA – cont’d [RNA] [three types:] rRNA – ribosomal
makes up the ribosomes

17. Name and explain the three types of rna to your partner.
Discuss
Name and explain the three types of rna to your partner.

18. Protein Synthesis transCription DNA  mRNA occurs in the nucleus
process begins at “promoter”
promoter tells where to start copying DNA sequence

19. Protein Synthesis transCription
enzyme unzips DNA but RNA bases pair instead of DNA bases
complementary bases are added

20. Protein Synthesis transCription
continue adding bases until a “termination sequence” is located.
mRNA carries message outside of the nucleus through nuclear pores into the cytoplasm

21. Protein Synthesis transLation mRNA  protein
ribosomes read mRNA and use tRNA to make proteins
steps:

22. Protein Synthesis transLation ribosomes clamp onto mRNA strand
finds “start” codon [AUG]
tRNA molecule containing matching anti-codon moves to ribosome
tRNA enters ribosome; attaches to strand

23. Protein Synthesis transLation another tRNA enters ribosome
ribosome bonds amino acids [peptide bond]
first tRNA leaves, another enters
repeat until “stop” codon is reached

24. Write this down!
Any nitrogen bases that are BEFORE the “start” or AFTER the “stop” are NOT translated into amino acids.

25. Protein Synthesis transLation
result – chain of amino acids linked by peptide bonds
= polypeptide
= protein
polypeptide processed and shipped using ER & Golgi.

26. Let’s Try It C C A T A C G G T G T C T C C G A T A T T T T A
is this DNA or RNA? how do you know?
transcribe the DNA into mRNA
C C A T A C G G T G T C T C C G A T A T T T T A
G G U A U G C C A C A G A G G C U A U A A A A U
find the start codon [AUG]

27. Let’s Try It G G U A U G C C A C A G A G G C U A U A A A A U
beginning with AUG, separate your mRNA into codons.
A U G / C C A / C A G / A G G / C U A / U A A / A A U
beginning with your AUG, translate your mRNA into amino acids
keep translating until “stop” codon is reached

28. Codon Chart

29. Let’s Try It A U G / C C A / C A G / A G G / C U A / U A A / A A U
MET / PRO / GLN / ARG / LEU / (stop) 