DNA Replication: 3 Stages: - Figure 10-9 - page 187 1. Unwinding DNA helicase unwinds and separates the two strands of the molecule, exposing the bases. This is called the “Replication Fork” DNA replication animation- v. realistic but hard to follow replication - it does have primerase and polymerase 1
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)
- 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
- it also connects the sugars and phosphate sides of the new strand using dehydration synthesis reactions.
- 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
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.
- 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.
- 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
- this process continues in steps until all of the lagging strand is replicated
- 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.
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.)
What is the significance of the order of the nitrogenous bases?
Protein Synthesis DNA - a ____________ for making proteins. BLUEPRINT
A 2 Step Process: 1. Transcription: the information is copied form the DNA molecule to a mRNA molecule
2. Translation: the information in the mRNA is “read” in the ribosome and “translated” by a tRNA to make a protein.
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
http://www.youtube.com/watch?v=NJxobgkPEA o&mode=related&search= http://www.youtube.com/watch?v=NJxobgkPEA o&mode=related&search Protein synthesis video Youtube videos - protein synthesis
Therefore, the DNA molecule simply tells the cell the order of amino acids necessary to make proteins.
Nucleic Acids: Material: DNA vs RNA - compare and contrast.
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.
The 3types of RNA are all created the same way: by TRANSCRIPTION o The 3types of RNA are all created the same way: by TRANSCRIPTION of the DNA molecule. 3 types of RNA: 1. RiBOSOMAL: together with some proteins, they make up the structure of RIBOSOMES
2. MESSENGER: used to deliver the instructions from the DNA to the RIBOSOMES for protein synthesis
3. TRANSFER: ”reads” the instructions and deliver the appropriate AMINO ACID to the ribosome.
Why doesn’t the mRNA just stay inside the nucleus?
DNA in the nucleus is safe DNA in the cytoplasm can be destroyed
Try “DECODING” this piece of DNA Code DNATACGGACAGTAAATT mRNA Amino acids DNATACGGACAGTAAATTmRNAAUGCCUGUCAUUUAA Methi- onine prolinevaline isoleuc ine stop
Great video on a cell’s life functions: http://www.studiodaily.com/main/searchlist/685 0.html http://www.studiodaily.com/main/searchlist/685 0.html Here is the explanation of what is happening: http://sparkleberrysprings.com/innerlifeofcell.ht ml http://sparkleberrysprings.com/innerlifeofcell.ht ml Protein Production
Types of Mutations Deletion Addition Substitution Positive Neutral Negative Mutagens 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-----
Another example: Original message: THE BIG DOG BIT TED AND RAN OFF --- --- ADDITION/FRAMESHIFT THE BIG FDO GBI TTE DAN DRA NOF F-- Changing the sequence