1. Unit 5: DNA and Protein Synthesis

2. Part 1: What is DNA? and History of DNA
Objectives:
Identify what DNA is
Trace the history of DNA and its discovery

3. What is DNA? DNA is an acronym that stands for deoxyribonucleic acid.
It indirectly controls all the functions of your body by telling ribosomes how to make proteins.

4. The history…
In the early 1950’s scientists thought that proteins were the genetic material.
In 1952 Alfred Hershey and Martha Chase performed an experiment with viruses that proved that DNA was the genetic material.

5. More history…
In 1953, James Watson and Francis Crick accurately described the structure of DNA.
They could never have done this without the help of Rosalind Franklin but, because she was a woman, she was denied credit for decades.

6. Summary Questions! What does DNA stand for?
What 2 people were credited with the discovery of DNA?
Who was also involved but received no credit?

7. Part 2: DNA Structure Objectives: Describe the structure of DNA
Identify the parts of a nucleotide
Describe base pairing

8. DNA structure DNA is a double helical structure. (double helix)
It looks like a twisted ladder.

9. A close-up…

10. DNA is Made of Nucleotides
Nucleotides are molecules that make up the structure of DNA.
A simple sugar (in DNA it’s called deoxyribose)
A phosphate group
A nitrogenous base pair (AT or CG)

11. How do the pieces fit together?
The sugar and phosphate groups make up the backbone or sides of the ladder.
The bases fit in the middle like the teeth of a zipper or the rungs of the ladder.

12. Nitrogenous Pairs There are two groups of base pairs. The purines:
Adenine (A)
Guanine (G)
The pyrimidines:
Thymine (T)
Cytosine (C)

13. Base Pairing Adenine (A) always pairs up with thymine (T).
Cytosine (C) always pairs with guanine (G).
Purines pair with pyrimidines

14. An Example…
DNA1: ATG CGC GGG ATT
DNA 2:
TAC
GCG
CCC
TAA

15. Summary Questions Pt. 2
The structure of DNA is called the _________ ___________.
A DNA Nucleotide contains ________, _________, and ___________.
Adenine always pairs with _______, Cytosine always pairs with ________.

16. Part 3: Replication Objectives: Describe the process of replication
Identify the products of DNA Replication

17. DNA replication
DNA replication is the process by which DNA copies itself.
It does this right before cell division so that the new cell has the same DNA as the original
This results in 2 identical strands of DNA, each with 1 of the original strands and 1 of the copies

18. How does it work?

19. The steps… 1. The double helix unzips.
2. The sugar and phosphates bond to make a new backbone.
3. Base Pairing: Free floating bases pair up with the bases on the DNA strands. (C-G, A-T)

20. Let’s see it again!
Play!

21. Summary (in class!) DNA Replication results in ____________.
The three steps of Replication are:
__________________

22. Part 4: Transcription and Translation
Objectives:
Identify the differences between RNA and DNA
Identify the different types of RNA molecules
Describe the processes of Transcription and Translation

23. What is RNA?
RNA, ribonucleic acid, is different from DNA in four major ways:
It is single stranded.
It can leave the nucleus
3. The sugar is ribose.
4. RNA has uracil (U) instead of thymine (T).

24. Types of RNA
mRNA = messenger RNA is made in the nucleus and, unlike DNA, can leave through the nuclear envelope.
rRNA = ribosomal RNA makes up ribosomes
tRNA = tranfer RNA delivers amino acids to the protein to be assembled.

25. Transcription
Transcription is the process by which mRNA is made from DNA.

26. Steps of Transcription
The process begins when enzymes unzips part of the molecule of DNA.
Free RNA nucleotides form base pairs with the DNA. The mRNA nucleotides bond together.
The mRNA strand breaks away and the DNA strands rejoin.

27. Translation
The process by which RNA is used to make proteins is known as translation.
It happens in five steps.

28. Steps of Translation 2. The first tRNA molecule attaches to the mRNA.
1. A ribosome attaches to the mRNA strand. tRNA approaches the ribosome.
2. The first tRNA molecule attaches to the mRNA.
3. A second molecule attaches and its amino acid peptide bonds to the amino acid of the first tRNA.
4. The ribosome moves down the mRNA and releases the tRNA that no longer has an amino acid attached to it.
5. The process repeats until the stop codon is reached.

30. What’s a codon?
A group of 3 bases that codes for a specific amino acid
Amino acids make up proteins

31. Find the amino acid or command:
ACC _______________________
UAG _______________________
AUG _______________________
GGG _______________________
UUA _______________________
AUC _______________________
CCC _______________________

32. Use the circular chart this time
AUG ___________________________
AAA ___________________________
UUU ___________________________
UAG ___________________________
CGC ___________________________
GGA ___________________________

33. Summary Questions Pt. 4 RNA differs from DNA in that:
______________
Transcription results in ______________
Translation results in ________________
The codon AUG codes for ____________