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Topic Five Nucleic Acids Name: 7.1 S.1 Analysis of results of the Hershey and Chase experiment providing evidence that DNA is the genetic material. (Slides 4-6) Use the hyperlink https://www.youtube.com/watch?v=Wxvd55XGrqc or the ppt. to view an animation about the Hersey-Chase experiment then answer the 3 questions below: 1. Explain why sulphur was used in one experiment and phosphorus in the other.

2. Explain why most of the radioactive sulphur (35S) was found in the supernatant.

3. Explain why little of the radioactive phosphorous (32P) was found in the supernatant, i.e. most remained

in the pellet.

Rosalind Franklin’s and Maurice Wilkins’ investigation of DNA structure by X-ray diffraction. When X-rays are directed at a material some is scattered by the material. This scattering is known as diffraction. For X-ray diffraction to work well the material ideally should be crystallised so that the repeating pattern causes diffraction to occur in a regular way. DNA cannot be crystallised but the molecules were arranged regularly enough for the technique to work. 4. Use the animation (http://www.dnalc.org/view/15874-Franklin-s-X-

ray.html) to understand how to interpret the Rosalind Franklin’s and

Maurice Wilkins’ X-ray diffraction photographs of DNA. To the right is

an example of a X-ray diffraction photograph of DNA.

n.b. Your answers to the questions below may well be helped by

diagrams.

a. What can be deduced from the X-shaped pattern?

Nature of Science: Rosalind Franklin’s careful observation and interpretation of the photographic evidence was crucial to Crick’s and Watson’s successful discovery of the structure of DNA. Her work and her calculations were shown to Crick and Watson without her permission and they subsequently published their model before she had an opportunity to publish her work. Her work is now is widely recognised as being as important to the discovery of DNA as Crick and Watson, but unfortunately she has never shared in the Nobel prize awarded to Crick and Watson as Nobel prizes cannot be given posthumously (Franklin died in 1958 aged just 37).

http://undsci.berkeley.edu/images/us101/x

ray.jpg

Topic Five Nucleic Acids Name: 2.6 U.1 The nucleic acids DNA and RNA are polymers of nucleotides. (includes 2.6 S.1 Drawing simple diagrams of the structure of single nucleotides of DNA and RNA, using circles, pentagons and rectangles to represent phosphates, pentoses and bases.) 5. Label and annotate the structures of this single nucleotide (number each Carbon). (Slide 9)

a.

b.

c.

6. State the type of bond that joins a to b and b to c. (Slides 10-11)

7. Complete the table below to show the pairings of the bases in DNA and RNA. (Slide 13)

Purine Pyramidine

8. In the space below, draw a single strand of three nucleotides, naming the bonds between them and

showing the correct relative position of these bonds. (Slide 11)

Topic Five Nucleic Acids Name:

10. Explain why the DNA helix is described as anti-parallel. (Slides 12-15)

2.6 U.3 DNA is a double helix made of two antiparallel strands of nucleotides linked by hydrogen bonding between complementary base pairs. 11. In the space below, draw a section of DNA, showing two anti-parallel strands of four nucleotides each.

(Slides 12 and 16)

2.6 U.2 DNA differs from RNA in the number of strands present, the base composition and the type of pentose. 12. Complete the table to distinguish between RNA and DNA. (Slide 17)

RNA DNA

Bases

Adenine (A) Guanine (G) Uracil (U)

Cytosine (C)

Sugar

Number of strands

Two anti-parallel,

complementary strands form a

double helix

Topic Five Nucleic Acids Name: 2.6 A.1 Crick and Watson’s elucidation of the structure of DNA using model making.

Whilst others worked using an experimental basis Watson and Crick used stick-and-ball models to

test their ideas on the possible structure of DNA. After reading the article Envisioning DNA: The

Nature of Science and the Search for the Double Helix and watching Tedtalk James Watson: How

we discovered DNA Answer the questions below (Slides 18-19)

13.

a. State two benefits of modelling over an experimental approach.

b. Outline the reasons was their first model was rejected.

c. Because of the visual nature of Watson and Crick’s correct model of DNA led to other discoveries.

List the two key discoveries concerning of DNA that were found quickly after the model was

published.

d. Modelling alone cannot lead to discoveries. Watson and Crick’s work was based on the

experiments and insight of others. Give an example of the work of other scientists that supported

their discovery.

14. What are the two roles that DNA plays in living things (Slide 23)

I. DNA Replication 2.7 U.1 The replication of DNA is semi-conservative and depends on complementary base pairing. 15. Explain how complementary base pairs are arranged. (Slide 27)

16. Explain why DNA replication of this kind of referred to as being semi-conservative. (Slides 27- 28)

Topic Five Nucleic Acids Name: 2.7 S.2 Analysis of Meselson and Stahl’s results to obtain support for the theory of semi-conservative replication of DNA. (Slides 31-32) The image to the right details the three possible methods of DNA replication. Review your understanding of Meselson and Stahl’s experiments by using using the presentation, the McGraw and Hill animation (clear and accessible) or the Scitable article (Nature education) (more detailed).

17. Describe and explain the result found by centrifuging a mixture of DNA from generation 0 and 2. (2)

2.7 U.2 Helicase unwinds the double helix and separates the two strands by breaking hydrogen bonds. 17. What role does the enzyme Helicase play in the copying of DNA? (Slide 31)

2.7 U.3 DNA polymerase links nucleotides together to form a new strand, using the pre-existing strand as a template.

18. Label the diagram below. (Slide 34)

https://upload.w ikimedia.org/wikipedia/commons/a/a2/DNAreplicationModes.png

Topic Five Nucleic Acids Name: 2.7 A.1 Use of Taq DNA polymerase to produce multiple copies of DNA rapidly by the polymerase chain reaction (PCR). 19. Polymerase chain reaction (PCR) is a key technique in DNA manipulation and analysis.

a. State the main uses of PCR. (Slide 37)

b. Complete outline of the three keys steps in the process of PCR. (Slide 37)

Denaturation:

Annealing:

Elongation:

c. If one cycle of PCR yields two identical copies of the DNA sequence. Calculate how many copies

30 cycles would yield. (Slide 37)

II. Protein Synthesis

2.7 U.4 Transcription is the synthesis of mRNA copied from the DNA base sequences by RNA

polymerase. 2.7 U.5 Translation is the synthesis of polypeptides on ribosomes

24. What are the names of the two processes required for gene expression? (Slide 39)

25. Where do transcription and translation take place in the cell? (Slide 39)

2.7 U.6 The amino acid sequence of polypeptides is determined by mRNA according to the genetic code. 2.7 U.7 Codons of three bases on mRNA correspond to one amino acid in a polypeptide.

26. Define mRNA in terms of its function (slide 40)

27. Suggest why the length of mRNA molecules varies. (slide 40)

28. Define the term codon. (slide 40)

Topic Five Nucleic Acids Name: 2.7 U.6 The amino acid sequence of polypeptides is determined by mRNA according to the genetic code. 2.7 U.7 Codons of three bases on mRNA correspond to one amino acid in a polypeptide.

29. Outline the steps of transcription. (Slides 41-42)

2.7 U.8 Translation depends on complementary base pairing between codons on mRNA and anticodons on tRNA.

30. State the molecule on which anti-codons, which are complementary to codons, can be found.(Slide 45)

31. Sketch diagrams below to show translation and use the steps above as annotations. (Slides 44-47)

Topic Five Nucleic Acids Name: 2.7 S.1 Use a table of the genetic code to deduce which codon(s) corresponds to which amino acid. 2.7 S.3 Use a table of mRNA codons and their corresponding amino acids to deduce the sequence of amino acids coded by a short mRNA strand of known base sequence. 2.7 S.4 Deducing the DNA base sequence for the mRNA strand. Use the genetic code table to help answer the questions below.

32. Deduce the codon(s) that

translate for Aspartate.

33. If mRNA contains the base sequence CUGACUAGGUCCGGA

a. deduce the amino acid sequence of the polypeptide translated.

b. deduce the base sequence of the DNA antisense strand from which the mRNA was transcribed.

c. If mRNA contains the base sequence ACUAAC deduce the base sequence of the DNA sense

strand.

34. Transcribe and translate this DNA sequence.

DNA T A C G G G C C C G T G A C A G C C A C T

mRNA

Amino

acid

35. An mRNA strand has 76 codons. How many amino acids will be in the polypeptide?

The genetic code – how mRNA codons translate to amino acids

http://w w w .ib.bioninja.com.au/_Media/genetic_code.jpeg

Topic Five Nucleic Acids Name:

36. A polypeptide contains 103 amino acids. What is the length of the gene (unit = base pairs)?

37. A gene is 105kbp (kilobase pairs). How many amino acids are in the polypeptide?

Nature of Science: Looking for patterns, trends and discrepancies - there is mounting evidence that the environment can trigger heritable changes in epigenetic factors.

38. DNA and Genetics is fast evolving area of Biological research. One of the very interesting areas of

current research is Epigenetics. Read the article about Epigenetics on Learn Genetics

(http://learn.genetics.utah.edu/content/epigenetics/).

a. Outline what Epigenetics is a study of.

b. Discuss how Epigenetics both fits into the accepted understanding of DNA expression and how is

contrary to it.

2.4 U.1 Amino acids are linked together by condensation to form polypeptides. AND 2.4 S.1 Drawing molecular diagrams to show the formation of a peptide bond. 20. Condensation of amino acids is a anabolic chemical reaction. A chain of amino acids joined together is

called a polypeptide or a protein. These building reactions are part of a living things metabolism.

a. What organelle controls the formation of polypeptides? (Slide 46)

b. Draw and annotate a structural diagram below to outline how two generalized amino acids (i.e. use

the R-group nomenclature) into a dipeptide through condensation, producing a peptide bond. (Slide

50)

c. Draw and annotate a structural diagram below of a generalized amino acid (label the two

functional groups in the diagram). (Slide 51)

Topic Five Nucleic Acids Name: 2.4 U.2 There are 20 different amino acids in polypeptides synthesized on ribosomes. 21. How many different amino acids do we know of? (Slide 53)

42. List three examples of amino acids synthesized by ribosomes. (Slide 53)

2.4 U.3 Amino acids can be linked together in any sequence giving a huge range of possible polypeptides.

43. State the three key ideas that explain the huge range of possible polypeptides: (Slides 54-56)

22. If a polypeptide contains just 5 amino acids calculate the how many different polypeptides can be

created.

2.4 U.4 The amino acid sequence of polypeptides is coded for by genes. 23. Outline the central dogma of genetics. (Slide 58)

2.4 U.6 The amino acid sequence determines the three-dimensional conformation of a protein. 2.4 U.5 A protein may consist of a single polypeptide or more than one polypeptide linked together.

24. The R-groups of an amino acid are classified as having one of a number of different properties. List the

properties can they possess. (Slide 59)

Topic Five Nucleic Acids Name: 25. Outline the four different levels of protein structure. (Slide 65)

Notes Fibrous or Globular

Primary

(polypeptide)

• The order / sequence of the amino acids of which the

protein is composed

• Formed by covalent peptide bonds between adjacent

amino acids

• Controls all subsequent levels of structure

Neither (– will fold to

become one of the

subsequent levels of

structure)

Secondary

Tertiary

Quaternary

26. Distinguish between globular and fibrous proteins (Slides 66-67)

Fibrous Globular

Shape

Function/Role

Solubility

Amino acid

sequence

Stability

Examples

Topic Five Nucleic Acids Name: 2.4 U.7 Living organisms synthesize many different proteins with a wide range of functions. 2.4 A.1 Rubisco, insulin, immunoglobulins, rhodopsin, collagen and spider silk as examples of the range of protein functions. 27. Complete the table to describe each of different functions that proteins have in and outside of cells.

(Slides 68-69)

Function Description Key examples

Rubisco

Muscle contraction Actin and myosin together cause the muscle contractions used in

locomotion and transport around the body.

Tubulin is the subunit of microtubules that give animals cells their

shape and pull on chromosomes during mitosis.

Fibrous proteins give tensile strength needed in skin, tendons,

ligaments and blood vessel walls. collagen

Blood clotting

Proteins in blood help transport oxygen, carbon dioxide, iron and

lipids.

Cell adhesion

Membrane transport

Insulin

Receptors

Binding sites in membranes and cytoplasm for hormones,

neurotransmitters, tastes and smells, and also receptors for light in

the eye and in plants.

rhodopsin

Packing of DNA

This is the most diverse group of proteins, as cells can make huge

numbers of different antibodies. immunoglobulins

Topic Five Nucleic Acids Name: 2.4 U.8 Every individual has a unique proteome. 28. The proteome is unique to every individual.

a. Define the term proteome. (Slide 76)

b. What affects the type of proteome exists? (Slide 76)

c. What is a genome? (Slide 77)

2.4 A.2 Denaturation of proteins by heat or by deviation of pH from the optimum. 29. Describe the term denaturation. Refer to the structure of the protein in your answer. (Slide 79)

30. What factors can commonly cause denaturation and how? (Slide 79)

31. What is an adaptation the Thermophiles have that make life possible of them? (Slide 80)

2.5 U.1 Enzymes have an active site to which specific substrates bind. (Use the hyperlink below) http://highered.mheducation.com/sites/0072495855/student_view0/chapter2/animation__how_enzymes_work.html

32. Define the following terms: (Slide 83)

a. Enzyme

b. Active site

c. Substrate

d. Product

2.5 U.2 Enzyme catalysis involves molecular motion and the collision of substrates with the active site. Play with the animation, by changing concentrations. 33. State what is meant by the term collision in enzyme catalysis. (Slide 141)

Topic Five Nucleic Acids Name: 34. Explain why not all collisions between enzymes and substrates result in catalysis. (Slide 87)

2.5 U.3 Temperature, pH and substrate concentration affect the rate of activity of enzymes.

35. List the factors that affect the rate at which enzymes work (Slide 90)

* * * *

* * *

36. Explain the effects of temperature, pH and substrate concentration on the rate of an enzyme-controlled

reaction.

Temperature (Slide 91)

pH (Slides 95-97)

Topic Five Nucleic Acids Name:

Substrate concentration (Slide 97)

2.5 U.4 Enzymes can be denatured. (Slide 98) 37. With the use of annotated diagrams explain how the denaturing of an enzyme affects its ability to

catalyse reactions.

2.5 U.5 Immobilized enzymes are widely used in industry

38. Enzymes used in industry are commonly immobilized.

a. Describe the advantages of immobilizing enzymes. (Slide 99)

b. List three ways in which enzymes can be immobilized. (Slide 99)

39. List eight common uses of enzymes in industry. (Slide 100)

2.5 A.1 Methods of production of lactose-free milk and its advantages.

40. Although all children produce lactase some adults are lactose intolerant, they lose the ability to produce

lactase in adulthood. Explain why. (Slide 108)

Topic Five Nucleic Acids Name:

a. State the three other commercial reasons that lactose free milk is produced. (Slide 111)

b. Outline the process by which lactose-free milk is produced by immobilized enzymes. (Slide 111)