Genetic control of protein structure and function

1. Genetic control of protein structure and function AS Biology. Gnetic control of protein structure and function

2. The structure of DNA and RNA • Genetic material of living organisms is either DNA or RNA. • DNA – Deoxyribonucleic acid • RNA – Ribonucleic acid • Genes are lengths of DNA that code for particular proteins. AS Biology. Gnetic control of protein structure and function

3. DNA and RNA are polynucleotides • Both DNA and RNA are polynucleotides. • They are made up of smaller molecules called nucleotides. • DNA is made of two polynucleotide strands: • RNA is made of a single polynucleotide strand: Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide Nucleotide AS Biology. Gnetic control of protein structure and function

4. A nucleotide is made of 3 components: A Pentose sugar This is a 5 carbon sugar The sugar in DNA is deoxyribose. The sugar in RNA is ribose. Structure of a nucleotide AS Biology. Gnetic control of protein structure and function

5. A Phosphate group Phosphate groups are important because they link the sugar on one nucleotide onto the phosphate of the next nucleotide to make a polynucleotide. Structure of a nucleotide AS Biology. Gnetic control of protein structure and function

6. A Nitogenous base In DNA the four bases are: Thymine Adenine Cytosine Guanine In RNA the four bases are: Uracil Adenine Cytosine Guanine Structure of a nucleotide AS Biology. Gnetic control of protein structure and function

7. Pyramidines Thymine - T Cytosine - C Uracil - U Purines Adenine - A Guanine - G Nitrogenous bases – Two types AS Biology. Gnetic control of protein structure and function

8. Adenine AS Biology. Gnetic control of protein structure and function

9. Guanine AS Biology. Gnetic control of protein structure and function

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11. Nucleotides are connected to each other via the phosphate on one nucleotide and the sugar on the next nucleotide A Polynucleotide Sugar phosphate bonds (backbone of DNA) AS Biology. Gnetic control of protein structure and function

12. James Watson (L) and Francis Crick (R), and the model they built of the structure of DNA AS Biology. Gnetic control of protein structure and function

13. X-ray diffraction photograph of the DNA double helix AS Biology. Gnetic control of protein structure and function

14. The Nitrogenous Bases pair up with other bases. For example the bases of one strand of DNA base pair with the bases on the opposite strand of the DNA. Base pairing AS Biology. Gnetic control of protein structure and function

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18. The Rule: • Adenine always base pairs with Thymine (or Uracil if RNA) • Cytosine always base pairs with Guanine. • This is beacuse there is exactly enough room for one purine and one pyramide base between the two polynucleotide strands of DNA. AS Biology. Gnetic control of protein structure and function

19. Complementary base pairing Purines Pyramidines Adenine Thymine Adenine Uracil Guanine Cytosine AS Biology. Gnetic control of protein structure and function

20. Nature of the Genetic Material • Property 1 - it must contain, in a stable form, information encoding the organism’s structure, function, development and reproduction • Property 2 - it must replicate accurately so progeny cells have the same genetic makeup • Property 3 - it must be capable of some variation (mutation) to permit evolution AS Biology. Gnetic control of protein structure and function

21. Replication of DNA and Chromosomes • Speed of DNA replication: 3,000 nucleotides/min in human 30,000 nucleotides/min in E.coli • Accuracy of DNA replication: Very precise (1 error/1,000,000,000 nt) AS Biology. Gnetic control of protein structure and function

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25. Taylor and co-workers (1957) after one further replication in unlabelled media 3H-labelled chromosomes AS Biology. Gnetic control of protein structure and function

26. Meselson and Stahl (1958) AS Biology. Gnetic control of protein structure and function

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28. A replicating Drosophila chromosome AS Biology. Gnetic control of protein structure and function

29. Success criteria

30. 1. To discuss the process of DNA replication

31. Origins initiate replication at different times. AS Biology. Gnetic control of protein structure and function

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36. Sequence the order of the enzymes AS Biology. Gnetic control of protein structure and function

37. Complete the parts whole map AS Biology. Gnetic control of protein structure and function

38. Sequence DNA replication: DNA unwinds via enzyme helicase (this forms a replication bubble and replication forks) Two semi-conservative DNA molecules have been produced Ligase joins okazaki fragments together on lagging strand DNA polymerases (3) start synthesising complementary bases to DNA strands in 3’ – 5’ direction (old strand number). Replication bubble extends in one 3- 5 direction leading to one strand becoming the leading strand, the other the lagging strand. AS Biology. Gnetic control of protein structure and function

39. Sequence DNA replication: ANSWERS 1. DNA unwinds via enzyme helicase (this forms a replication bubble and replication forks) 5. Two semi-conservative DNA molecules have been produced 4. Ligase joins okazaki fragments together on lagging strand 2. DNA polymerases (3) start synthesising complementary bases to DNA strands in 3’ – 5’ direction (old strand number). 3. Replication bubble extends in one 3- 5 direction leading to one strand becoming the leading strand, the other the lagging strand.

40. Extended Abstract Discuss what the consequence would be to the new cells in DNA replication was not 100% accurate. Explain what factors (TWO) ensure errors are prevented. AS Biology. Gnetic control of protein structure and function

41. Answer The consequence for the new cells if DNA replication was not accurate would be a change in the sequence of bases. This change could lead to genes producing different proteins or no proteins at all. Many of these genes code for enzymes the cell may not be able to carry out in desired functions (e.g. a nerve cell). Errors are minimised by the DNA being double stranded so complementary bases will always be matched up. When DNA polymerase is adding free nucleotides to the new strand only the correct base pair will be matched up. This ensures the new strand will have the correct complementary base sequence.

42. 1. To discuss the process of DNA replication

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