KEY CONCEPT DNA structure is the same in all organisms.

1. KEY CONCEPT DNA structure is the same in all organisms.

2. We love D N A Made of nucleotides Sugar, Phosphate and a Base Bonded down one Side Adenine and Thymine Make a Lovely Pair Cytosine without Guanine Would feel very bare • O-O-O deoxy-ribo-nucleic acid • R-N-A is ribo-nucleic acid

3. phosphate group nitrogen-containing base deoxyribose (sugar) • DNA is made up of a long chain of nucleotides • Each nucleotide has three parts • Sugar – deoxyribose • Phosphate group • a nitrogen-containing Base

4. The nitrogen containing bases • - Adenine (A) • - Thymine (T) • - Cytosine (C) • - Guanine (G) • * Purines – have 2 rings = Adenine & Guanine • * Pyrimidines – have 1 ring = Cytosine & Thymine

5. Watson and Crick determined the three-dimensional structure of DNA • 1953 • Two nucleotide chains that wrap around each other to form a double spiral (double helix) • Temperature liable – a change in T can break apart the DNA strand

6. Rosalind Franklin and Erwin Chargaff. • Franklin’s x-ray images suggested that DNA was a double helix of even width. • Chargaff’s - Complementary Base Pairing - A=T and C=G

7. G C A T Nucleotides always pair in the same way. • Because a pyrimidine (single ring) pairs with a purine (double ring) • A-T • C-G

8. covalent bond hydrogen bond • The backbone is connected by covalent bonds • Very Strong • The bases are connected by hydrogen bonds • Easily formed & easily broken

9. 8.3 DNA Replication • DNA is replicated during theS phase of interphase • Inside the nucleus

10. 8.3 DNA Replication nucleotide The DNA molecule unzips in both directions. DNA serves as a template. 1. Helicase – (Enzyme) breaks the Hydrogen bonds between the bases • Replication Fork– point at which the two chains separate (last bond broken)

11. 8.3 DNA Replication nucleotide new strand DNA polymerase • New complimentary nucleotide bases pair up on both sides of old DNA template • A pairs up with complement T • C pairs up with complement G • DNA polymerase(Enzyme) forms new Hydrogen bonds between the nucleotides

12. 8.3 DNA Replication new strand original strand Two molecules of DNA • Two new exact copies of DNA are formed, each with an original strand and a newly formed strand.

13. 8.3 DNA Replication Replication is fast and accurate. • DNA replication starts at many points in eukaryotic chromosomes. • Mutation – change in the nucleotide sequence • DNA polymerases can find and correct errors. • One error per 1 billion nucleotides

14. 8.4 Transcription • RNA differs from DNA in three major ways. • RNA • Sugar = Ribose • Base - Uracil instead of thymine. • U - A • 3. Shape - single-stranded

15. 8.4 Transcription Three types of RNA. Mesenger RNA (mRNA) – single uncoiled chain • carries genetic information from the DNA in the nucleus to the cytoplasm Transfer RNA (tRNA) – single chain of about 80 nucleotides • folded into a hairpin shape • binds to specific amino acids Ribosomal RNA (rRNA) – makes up the ribosomes where proteins are made

16. 8.4 Transcription transcription complex start site nucleotides • Process of copying DNA into mRNA • Transcription starts when • RNA polymerase (enzyme) - binds to a Promoteron DNA • breaks H-bonds and makes H-bonds • One chain is used as a template • mRNA = transcript • Transcription stops when • RNA polymerase reachesa Terminator

17. 8.4 Transcription one gene growing RNA strands DNA Transcription vs Replication. • Replication copies all the DNA • Transcription copies only a gene.

18. 8.5 Translation KEY CONCEPT Translation converts an mRNA message into a protein.

19. 8.5 Translation codon for methionine (Met) codon for leucine (Leu) Amino acids are coded by mRNA base sequences. • Codon – 3 nucleotides of mRNA • AUG = start • UAA, UAG, UGA = stop

20. 8.5 Translation • The genetic code matches each codon to its amino acid

22. 8.5 Translation • tRNA – transports amino acids to the ribosomes • Anticodon – tRNA sequence of 3 nucleotides • complementary to an mRNA codon.

23. 8.5 Translation Translation takes place at the Ribosomes Ribosomes that are attached to the endoplasmic reticulum build proteins for use outside cell Ribosomes that are free floating make proteins for use inside cell

24. 8.5 Translation • For Translation to begin - Ribosomes attaches to a start codon on mRNA (AUG) • Start codon pairs with the anticodon on tRNA (UAC) • codes for the first amino acid – methionine • may be removed later if not needed

25. 8.5 Translation • Amino acids are bonded together with peptide bonds

26. 8.5 Translation • Once the stop codon is reached, the ribosome releases the protein

27. 8.6 Gene Expression and Regulation KEY CONCEPT Gene expression is carefully regulated in both prokaryotic and eukaryotic cells.

28. 8.6 Gene Expression and Regulation • An operator is a part of DNA that turns a gene “on” or ”off.” • The lac operon was one of the first examples of gene regulation to be discovered. • has three genes that code for enzymes that break down lactose • – milk sugar

29. 8.6 Gene Expression and Regulation • RNA processing • Introns are nucleotides that are removed from mRNA • Exons are the nucleotides that are spliced together. • Processed mRNA (transcript) goes to ribosome to be made into a protein

30. 8.6 Gene Expression and Regulation • Coding DNA (genes)  make proteins • Humans = 20,000 • Non-coding DNA (genes)  make RNA • Transcribed but never Translated • Human = 500 • Human Total = ~ 20,500 genes