1. Bell Work What type of bond holds nucleotide bases together and why is it important?

2. Important Vocabulary  Genes- segment of DNA; structural/functional unit of heredity; each contains genetic info. that tells the cell to make specific protein  Chromosome- a long strand of tightly bound DNA  DNA- double stranded, helical nucleic acid molecule that determines the inherited structure of cell’s proteins  Replication- process of copying DNA prior to cell division (mitosis/meiosis)

3. DNA Replication  Purpose: To create an exact copy of DNA for new cell  Late in interphase (S Phase)  DNA separates into 2 strands; each strand serves as a template for a new strand  Cell goes through mitosis or meiosis

5. Prophase Metaphase Anaphase Telophase & Cytokinesis

6. A Closer Look…  Each of your cells has 46 DNA molecules in its nucleus (one long double helical molecule per chromosome)  We have 6 billion base pairs that can be copied in a couple of hours

7. Where Replication Begins:  Begins at sites called the origins of replication (there are many)  Proteins initiate DNA replication The two strands separate at the replication fork, and create a replication bubble  DNA replication proceeds in both directions until copying is finished!

8. First Step in replication  Helicase- unzips the molecule of DNA Breaks H bonds between base pairs Creates 2 DNA templates

9. 2 nd Step in Replication  Polymerase- joins individual nucleotides producing a new DNA strand; it also proofreads each new strand DNA strands are antiparallel (oriented in opposite directions) DNA strand elongates in a 5’-3’ direction (5’ leads w/ phosphate & 3’ leads w/ sugar) ○ The strand being built 5’-3’, has Polymerase continuously adding base pairs  leading strand ○ The strand that is built 3’-5’, has Polymerase synthesizing in segments  lagging strand (Okazaki fragments) DNA ligase eventually joins the fragments

11. C

12. 3. Telomerase- adds short repeated DNA sequences to the telomeres  Telomeres- DNA at the chromosome tips; difficult to replicate (especially lagging strands) Helps prevent genes from being lost or damaged in replication

14. Bell Work What is a mutation? Are they harmful or beneficial to you? Explain.

15. Mutations  What is a mutation?  Mistake in copying DNA  Heritable changes in genetic info

16. Harmful or Beneficial?  Harmful – change protein structure or gene activity dramatically Can disrupt normal biological activities  genetic disorders (ie. Genetic disorders)  Beneficial- proteins are altered in a way that causes positive/useful effects to organisms Can be useful to organisms in different or changing environments  Silent- an alteration in a DNA sequence that does not result in a change in protein

17. Problems with Replication- Mutations 1. Frame Shift Mutations Deletion Frameshift Mutation- A base is accidentally left out Insertion Frameshift Mutation- A base is accidentally inserted 2. Point Mutation/Substitution- The wrong base is substituted  Environmental agents or radiation may also change the base sequence- mutagens

18. Recall how DNA is read…  A sequence of DNA are like letters of a coded message telling our cells what protein to make.  DNA is decoded in sets of 3 (codon) Ie. THE KID ATE AND WAS FAT Ie. ATG CGG ATT ACG

19. Problems with Replication- Mutations 1. Deletion Frameshift Mutation- A base is accidentally left out Example: the big dog bit the cat but not the boy If a single base was deleted such as “o” in “dog”. The sentence would now read: the big dgb itt hec atb utn ott heb oy

20. Deletion Frameshift DNA strand:ACG TAG GTC TCG AAT Replicated strand: TGC ACC AGA GCT TA

21. Problems with Replication- Mutations 2. Insertion Frameshift Mutation- A base is accidentally inserted Example: the big dog bit the cat but not the boy If a single extra base was inserted such as “r” in “dog”, after the “o”. The sentence would now read: the big dor gbi tth eca tbu tno tth ebo y

22. Insertion Frameshift DNA strand:ACG TAG GTC TCG AAT Replicated strand: TGC AAT CCA GAG CTT A

23. Problems with Replication- Mutations 3. Point Mutation/Substitution- The wrong base is substituted Example: the big dog bit the cat but not the boy If the "d" in dog got replaced by a "p". The sentence would now read: the big pog bit the cat but not the boy

24. Point Mutation DNA strand:ACG TAG GTC TCG AAT Replicated strand: TCC ATC CAG AGC TTA

25. Identify the following mutation: 1. Original strand:TCG GTA ATC GAT Replicated strand:AGC ATT AGC TA ________________ 2. Original strand:TCG TAG AAG TAC Replicated strand:AA C ATC TTC TTG ________________

26. Let’s Do Lunch! Instructions: You will be given 2 minutes to fill in your lunch appointments (note: you can not repeat a luncheon appointment). Once you have your dates set, you will be given 5-7 minutes to “consume” the material given and “regurgitate” your answers!