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DNA Structure and Function Starr/Taggart’s Biology: The Unity and Diversity of Life, 9e Chapter 13.

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Presentation on theme: "DNA Structure and Function Starr/Taggart’s Biology: The Unity and Diversity of Life, 9e Chapter 13."— Presentation transcript:

1 DNA Structure and Function Starr/Taggart’s Biology: The Unity and Diversity of Life, 9e Chapter 13

2 Key Concepts: DNA contains the information of heritable traits in all cells Each DNA strand consists of two strands of nucleotides twisted together Hereditary information is encoded in the sequence of nucleotides Nitrogen bases have specific pairing arrangements DNA is replicated before a cell divides

3 Discovery of DNA Function Fred Griffith - Discovered hereditary transformation

4 Discovery of DNA Function Griffith’s experiments Transfer of hereditary material from dead S cells to living R cells (transformation)

5 DNA Structure Nucleotides Deoxyribose Phosphate Group Nitrogen base –Adenine A –Guanine G –Thymine T –Cytosine C Pairing Arrangement –A - T –C – G Amount of A=T and C=G

6 Fig. 13.8, p. 220 Rosalind Franklin

7 Fig. 13.1, p XY James Watson and Francis Crick

8 Structure of DNA DNA consists of two strands of nucleotides held together at bases by hydrogen bonds –A=T and C=G The two strands twist into a double helix. The two strands run in opposite directions (anti-parallel) –Each strand runs in a 5’ to 3’ direction

9 Fig. 13.7, p nanometer diameter, overall distance between each pair of bases = 0.34 nanometer each full twist of the DNA double helix = 3.4 nanometers

10 Unlocking the Secret to Heredity The structure of DNA allows for one strand to act as a template for the other strand –If you have one strand you automatically know the sequence of base pairs for the other strand. ACGCGCT TGCGCGA

11 Semi-conservative Replication DNA Replication is semi-conservative There are 3 enzymes that are used for replicating a new strand of DNA –Helicase –DNA polymerase –Ligase

12 animation Click to view animation.

13 DNA Replication and Repair Enzyme regulated –Hydrogen bonds break –Attachment of nucleotides to new strands –DNA polymerases DNA ligases –New strand is half old, half new

14 Detailed Look at Replication Nucleotides can only be added in the 5’ to 3’ direction Leading Strand assembly is continuous Lagging strand discontinuous

15 Creating Clones Dolly the sheep was first mammal to be cloned from a differentiated cell –Nucleus from sheep udder cell was transferred into enucleated unfertilized egg –Egg grew into sheep by mitotic divisions Mice and cows have now also been cloned from adult cells

16 In Conclusion Hereditary information is located in DNA DNA consists of nucleotides DNA molecule consists of two nucleotide strands twisted into a double helix The bases of DNA strands pair in a constant fashion DNA of one species has specific nucleotide sequences


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