DNA

1. DNA Functions In Life processes

2. DNA Bases • All life is composed of 4 DNA bases: • Adenine • Guanine • Cytosine • Thymine

3. Three Parts to a DNA Monomer • DNA is composed of monomers called nucleotides. • Nucleotides have 3 parts: • Base (A,T,C,G) • Sugar (Deoxyribose) • Phosphate group

5. Chargaff’s Rules • Explain’s DNA base pairing. • Due to molecular configuration….. A = T C = G

6. Types of Bases • Purines: Adenine and Guanine • Larger, two ring structures • Pyrimidines: Thymine and Cytosine • Smaller single ring structures

8. Chargaff's Rules

9. DNA Replication • Process of copying DNA. Example: During chromosome duplication. • The DNA UNZIPS! Literally. It separates into two nucleotide chains. • The point at which DNA strands begin to separate is called the replication fork.

10. Remember: DNA is two strands that are wound together. • Enzymes called helicases unwind the DNA, it breaks the weak hydrogen bonds between bases. • Another enzyme, DNA polymerase, attaches to the replication fork site.

11. Free nucleotides are available within the nucleus, A – T – C – G. • DNA polymerase gathers these nucleotides and attaches them to both sides of the unziped DNA strands. • DNA polymerase moves like a train on a track, attaching complimentary base pairs to the original DNA.

12. Two new DNA strands eventually result. Exact copies of each other!

15. Protein Synthesis DNA’s Other Function

16. RNA • RNA is the genetic messenger boy for the cell. • RNA is made by the nucleolus. • RNA transfers genetic instructions out of the nucleus so protein products for life can be made.

17. RNA has four bases: • Adenine • Guanine • Cytosine • Uracil • Uracil replaces Thymine.

18. DNA NEVER LEAVES THE NUCLEUS! NEVER – NEVER! • Think of changing thymine to uracil as a safety precaution to keep DNA from escaping. • Complimentary bases for RNA are: • C = G • A = U

19. Types of RNA • Messenger RNA: (mRNA) A single, uncoiled chain of nucleotides that is copied from the nucleus. • Transfer RNA: (tRNA) Gathers amimo acids outside the nucleus to build protein. • Ribosomal RNA: (rRNA) Forms the ribosomes, site of protein synthesis.

21. Transcription • mRNA enters the nucleus and copies the part of DNA it needs to make a protein product. • Making a master blueprint. • This blueprint is the compliment (opposite) of the original.

22. A spot on a DNA strands that codes for a protein product is called a promoter. • RNA polymerase attaches to the promoter and signals DNA to unzip. • RNA copies one side of the open DNA molecule. • This continues till RNA reaches a termination signal molecule.

23. Translation • The blueprint that mRNA made leaves the nucleus. • This is used to build a protein product life needs to function. • Proteins are made of amino acids strung in long polypeptide chains.

24. In the nucleus, mRNA made 3-nucleotide sequence copies called codons. • Example: ACT – TTA – GCC. • Each codon stands for a particular amino acid. • It’s like reading a book!

25. mRNA meets up with rRNA (the ribosome) and attaches there. rRNA directs protein production. • tRNA comes along and reads the mRNA – actually it makes a complementary copy of the codon called an anti-codon. • The anti-codon is exactly the same as the original DNA strand!

26. tRNA carries an amino acid around with it that matches a specific nucleotide anti-codon. • tRNA attaches to its complimentary mRNA sequence, carrying its amino acid. • A second tRNA meets up with its mRNA compliment. • Attached amino acids form bonds.

27. Trasnslation begins with the start codon: AUG. • Translation ends with the stop codon: UAG (or UUA, or UGA) • When translation ends, a completed protein product – like insulin – drops off the tRNA.

30. Amino Acids • There are only 20 amino acids that code for protein. • There are 64 possible codon combinations. • Thousands of proteins are made!

32. Additional Facts • DNA inside the nucleus has regions that code for proteins and regions that do not. • Exons: DNA that codes for protein. • Introns: DNA that does not code. Nonsense DNA? We’re not sure yet.

33. Life regulates how much of a protein product is made. • Inducer or promoter enzymes signal when a product is needed, and activates the unzipping of DNA. • Repressor proteins won’t let DNA zip if enough of a protein product is available.

34. This Whole Process Is Called Gene Expression