1. Chromosome Abnormalities Non-disjunction during meiosis can cause a gamete to have an extra chromosome Trisomy = three copies of the same chromosome. Most are lethal before birth, but three of chromosome 21 causes Down syndrome.

2. Trisomy of Chromosome 21

3. Chapter 10 DNA Replication and Expression

4. DNA (Deoxyribose Nucleic Acid) Polymer made of subunits called nucleotides Nucleotides have three parts – Phosphate – Sugar (deoxyribose) – Nitrogen bases

5. Four Nitrogen bases of DNA (9.1) Adenine Guanine Cytosine Thymine

6. DNA structure (Fig. 10-2) Double helix – James Watson and Francis Crick (Nobel Prize) – Two strands held together by hydrogen bonds Bases are paired up: – Adenine to Thymine – Cytosine to Guanine DNA is twisted (helix)

8. X Ray Crystallography of DNA (10.3)

9. DNA wraps around proteins (histones) to form chromatin. Chromatin coils up into chromosomes. DNA inside a Eukaryote

10. DNA is Replicated Parent DNA strands act as templates for new DNA Strands separate and new bases are added to each side

11. DNA replication (10.6)

12. Helicase DNA polymerase Ligase DNA replication requires three enzymes (10.7)

13. DNA Expression

14. Central Dogma of Molecular Biology: DNA  RNA  Protein

15. Flow of Genetic Information (10.8)

16. What is RNA? Ribose Nucleic Acid Nucleic acid similar to DNA Three important differences – Single strand – Sugar is Ribose – Uracil instead of Thymine

17. DNA contains information used to make proteins 95% of DNA sequence is meaningless or “junk” 5% that has information is contained in genes Gene is a sequence of DNA that codes for a protein

18. DNA to Protein (10.10)

19. How a gene produces a protein Genes are TRANSCRIBED into messenger RNA mRNA goes to ribosomes for protein synthesis Transfer RNA carries Amino Acids to be assembled at the ribosomes mRNA is TRANSLATED into proteins.

20. Transcription 10.13

21. Transfer RNA

22. So how do we know what the amino acid order will be?

23. A gene sequence is divide into groups of three (codons)

24. Codons on mRNA are recognized by tRNA

25. Each codon codes for an amino acid

26. How are codons read? (10.10)

27. Viral genetics

28. What about viruses? Viruses are nucleic acids surrounded by a protein capsule. Viruses invade host cells by injecting their DNA Viral DNA incorporates into the host cell’s genome ( Lysogenic Phase) Viruses use their DNA to force host cells to produce more viruses ( Lytic Phase) Viruses do not fit into the cell theory.

29. Phage Virus Cycles (10.26)

30. Mutations Mistakes in copying of DNA Three types – Insertion – Deletion – Substitution

31. Consequences of mutations Most mutations are neutral – no noticeable effect on the protein Some mutations are deleterious – Genetic disorders – Cancer Some mutations may produce a “good” trait In both cases a change in the bases changes sequence of amino acids