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. • a 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), the helix has a uniform width. • A-T • C-G

8. covalent bond hydrogen bond • The backbone is connected by covalent bonds. • The bases are connected by hydrogen bonds.

9. 8.3 DNA Replication KEY CONCEPT DNA replication copies the genetic information of a cell.

10. 8.3 DNA Replication Replication copies the genetic information. • The rules of base pairing directreplication. • A-T • G-C • DNA is replicated during theS stage of interphase.

11. 8.3 DNA Replication nucleotide The DNA molecule unzips in both directions. Proteins (Enzymes) carry out the process of replication. • DNA serves as a template. • Helicase – enzyme that breaks the Hydrogen bonds between the bases • Replication Fork – point at which the two chains separate (last bond broken)

12. 8.3 DNA Replication nucleotide new strand DNA polymerase • New complimentary nucleotide bases pair up on both sides of old DNA template • DNA polymerase (enzyme) forms new Hydrogen bonds between the nucleotides

13. 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.

14. 8.3 DNA Replication There are many origins of replication in eukaryotic chromosomes. 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. • Error Rate - one error per 1 billion nucleotides

15. 8.4 Transcription • RNA differs from DNA in three major ways. 1. RNA has a ribose sugar. 2. RNA has uracil instead of thymine. • U - A 3. RNA is a single-stranded structure.

16. 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 • RNA nucleotides folded into a hairpin shape – • binds to specific amino acids Ribosomal RNA (rRNA) – makes up the ribosomes where proteins are made

17. 8.4 Transcription transcription complex start site nucleotides • Process of copying DNA into mRNA • RNA polymerase – starts RNA transcription by binding to specific regions of DNA • Promoters • RNA polymerase breaks H-bonds and makes H-bonds between the DNA bases • One chain is used as a template to build RNA (mRNA=transcript) • Transcription continues one nucleotide at a time until the RNA polymerase reaches a DNA region • termination signal

18. 8.4 Transcription one gene growing RNA strands DNA The transcription process is similar to replication. • The two processes have different end results. • Replication copiesall the DNA;transcription copiesa gene.

19. 8.5 Translation KEY CONCEPT Translation converts an mRNA message into a protein.

20. 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

21. 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 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 • A promotor is a DNA segment that allows a gene to be transcribed. • 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. • The lac operon has three genes that code for enzymes that break down lactose.

29. 8.6 Gene Expression and Regulation • RNA processing is also an important part of gene regulation in eukaryotes. • Introns are nucleotides that are removed and exons nucleotides that are spliced together.

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