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Presentation on theme: "DNA."— Presentation transcript:


2 Contents of the Nucleus

3 DNA vocab Deoxyribonucleic acid Chromosomes Chromatin Genes Genome

4 DNA Structure What is the structure called?
Who received the Nobel Prize for working out the molecular structure?

5 Building blocks of DNA What are the building blocks of DNA? (4 types)
What are the building blocks made of? (3 parts)

6 Polymerization of Nucleotides:

7 How do they fit together?
POLYMERIZATION… “rungs of the ladder” “sides”

8 Try “replicating” this single strand of DNA

9 DNA Replication: 3 Stages: - Figure 10-9 - page 187
replication - it does have primerase and polymerase 1 DNA replication animation- v. realistic but hard to follow 1. Unwinding DNA helicase unwinds and separates the two strands of the molecule, exposing the bases. This is called the “Replication Fork”

10 2. Formation of the Complementary Strand
- the parental DNA strands act as a template - DNA polymerase attaches to the opened strands (one on each side)

11 - it “reads” the parental DNA strand and attaches the appropriate nucleotide to the template; A to T, G to C (and vise versa) DNA polymerase

12 - it also connects the sugars and phosphate sides of the new strand using dehydration synthesis reactions.

13 - DNA polymerase can only travel in one direction - from 3’ to 5’ , therefore, the 2 polymerases will travel in opposite directions in the replication forks


15 The pieces are joined together by DNA ligase
As the two DNA polymerases move along the DNA molecule, ONE will be following the DNA helicase, while the other one will be going in the opposite direction.

16 - the DNA polymerase that follows the helicase is on the “LEADING STRAND”
- the other polymerase is going to run into the “end” of the replication fork (where the helicase started to open the DNA helix) - it must detach at that point.

17 - a new polymerase will attach further up the “LAGGING STRAND” and synthesis a new daughter strand up to the point were the first polymerase began, and then IT will detach

18 - this process continues in steps until all of the lagging strand is replicated

19 - every time the polymerases detach, they leave a gap in the sugar-phosphate back-bone
- DNA ligase will travel along the newly synthesized strands, locate the gaps, and make the necessary connections to fill them.

20 Finally, both the leading strand and the lagging strands are “proof-read” by specific enzymes to ensure that the replication was accurate. ( if it wasn’t corrected, it would be called a MUTATION.)

21 What is the significance of the order of the nitrogenous bases?

22 Protein Synthesis DNA - a ____________ for making proteins. BLUEPRINT

23 A 2 Step Process: 1. Transcription: the information is copied form the DNA molecule to a mRNA molecule

24 Try Transcribing this piece of DNA into mRNA

25 2. Translation: the information in the mRNA is “read” in the ribosome and “translated” by a tRNA to make a protein.

26 Breaking “THE CODE”: DNA Molecules can be thought of as a type of “sentence”. - the bases, (A,T,G,C) make up the “letters” - these ‘letters” are arranged into “words” of three letters -called “triplets” - the triplets each have a specific “meaning” - they code of a specific amino acid THE CAT ATE THE RAT AUG CCG GCA AAG UAG Met pro ala lys stop

27 The Code: How do you follow the mRNA code?

28 Protein synthesis video
Protein synthesis video Youtube videos - protein synthesis

29 Therefore, the DNA molecule simply tells the cell the order of amino acids necessary to make proteins.

30 NucleicAcids: Material: DNA vs RNA - compare and contrast.

31 RNA: an intermediate between DNA and ribosomes
The same as DNA except: the sugar is RIBOSE instead of DEOXYRIBOSE  RNA is SINGLE-stranded the base “THYMINE” is replaced by URACIL.

32 The 3types of RNA are all created the same way: by TRANSCRIPTION of the DNA molecule.
1. RiBOSOMAL: together with some proteins, they make up the structure of RIBOSOMES

33 2. MESSENGER: used to deliver the instructions from the DNA to the RIBOSOMES for protein synthesis

34 3. TRANSFER: ”reads” the instructions and deliver the appropriate AMINO ACID to the ribosome.

35 Why doesn’t the mRNA just stay inside the nucleus?

36 DNA in the nucleus is safe
DNA in the cytoplasm can be destroyed




40 Try “DECODING” this piece of DNA Code
mRNA U Amino acids Methi-onine proline valine isoleucine stop DNA T A C G mRNA Amino acids

41 Great video on a cell’s life functions:
Here is the explanation of what is happening: Protein Production

42 Protein Structure


44 Recap: Genes WHAT are they? WHERE are they? How many genes do we have?
WHY are we storing the information for PROTEINS???

45 Preview: Enzymes WHAT are they? What do they do?
Why do our DNA molecules store the instructions to make them?

46 One Gene = One Protein? Human genome = approximately 25,000 genes
Number of proteins humans make is approximately 90,000. NOT SURE HOW THIS CAN BE!

47 Mutations - Define

48 Types of Mutations Deletion Addition Substitution Positive Neutral
Example: Deletion The result can be a completely non-functional protein…doesn’t make sense. i.e THE CAT ATE THE RAT--- If you delete a base (letter) ‘C’ ---THE ATA TET HER AT----- Deletion Addition Substitution Positive Neutral Negative Mutagens

49 Changing the sequence Another example: Original message:

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