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BIOLOGY, M5 EQ-Bank 23

Students conducted preliminary experiments to analyse the DNA base composition of five different individuals.

The table shows the experimental data collected.
 

  1. On the grid provided, plot the % Guanine against % Adenine of the individuals analysed and draw a suitable line of best fit.   (3 marks)
     
     

  2. Identify the relationship shown by the data.   (1 mark)

  3. Explain the relationship shown by the data.   (3 marks)

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a.   
       

b.  Relationship: As the % of Adenine increases, the % of Guanine decreases.

c.   Adenine/Guanine relationship

→ Because Adenine pairs with Thymine and Cytosine pairs with Guanine occurring to DNA base pairing rules, each should directly correlate to each other and account for the same % within the DNA composition of any species.

→ There are the only 4 components that make up all DNA composition. This also means that when comparing % of bases that do not pair, such as Adenine and Guanine, they must combine to form 50% of all DNA. This is evident when looking at individuals A and B, as well as C, D and E which are only off by 1-2%, most likely due to human error.

→ This always explains the relationship where an increase in Adenine (and Thymine) % will result in a decrease in Guanine (and Cytosine) % as the A and T pairs now occupy more space in the genome.

Show Worked Solution

a.   
       

b.  Relationship: As the % of Adenine increases, the % of Guanine decreases.

c.   Adenine/Guanine relationship

→ Because Adenine pairs with Thymine and Cytosine pairs with Guanine occurring to DNA base pairing rules, each should directly correlate to each other and account for the same % within the DNA composition of any species.

→ There are the only 4 components that make up all DNA composition. This also means that when comparing % of bases that do not pair, such as Adenine and Guanine, they must combine to form 50% of all DNA. This is evident when looking at individuals A and B, as well as C, D and E which are only off by 1-2%, most likely due to human error.

→ This always explains the relationship where an increase in Adenine (and Thymine) % will result in a decrease in Guanine (and Cytosine) % as the A and T pairs now occupy more space in the genome.

BIOLOGY, M5 2016 HSC 26

Students conducted preliminary experiments across different species to analyse their DNA base composition.

The table shows the experimental data collected.

 

  1. On the grid below, plot the % Adenine vs % Guanine of the species analysed AND draw a suitable line of best fit.   (3 marks)
     
     

     
  2. Identify the relationship shown by the data.   (1 mark)

  3. Explain the relationship shown by the data.   (3 marks)

Show Answers Only

a.  

b.  As % Adenine increases, the % Guanine decreases.
  

c.    Explanation of data relationship:

→ Adenine and Thymine are complementary base pairs. Likewise with Guanine and Cytosine.

→ It would therefore be expected that as the percentage of adenine increases, the percentage of thymine would also increase.

→ Adenine + Thymine + Cytosine + Guanine = 100%

→ It follows that as adenine increases the amount of guanine should decrease.

Show Worked Solution

a.  

b.  As % Adenine increases, the % Guanine decreases.
  

c.    Explanation of data relationship:

→ Adenine and Thymine are complementary base pairs. Likewise with Guanine and Cytosine.

→ It would therefore be expected that as the percentage of adenine increases, the percentage of thymine would also increase.

→ Adenine + Thymine + Cytosine + Guanine = 100%

→ It follows that as adenine increases the amount of guanine should decrease.


♦♦♦ Mean mark (c) 28%.

BIOLOGY, M5 2015 HSC 23

The diagram shows a model involving DNA.
 

  1. What process is being modelled?   (1 mark)

  2. Identify TWO structural features of the DNA molecule which are NOT shown in this model.   (2 marks)

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a.   DNA replication

b.   Successful answers should include two of the following:

→ the double helix.

→ the sugar-phosphate backbone.

→ hydrogen bonds (connecting base pairs)

Show Worked Solution

a.   DNA replication

b.   Successful answers should include two of the following:

→ the double helix.

→ the sugar-phosphate backbone.

→ hydrogen bonds (connecting base pairs)


Mean mark (a) 53%.

BIOLOGY, M5 2019 HSC 4 MC

The figure shows a part of a DNA molecule.

How many complete nucleotides are shown in the figure?

  1. 1
  2. 2
  3. 4
  4. 8
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Show Worked Solution

→ Nucleotides are made up of one base, one sugar and one phosphate.

→ The diagram therefore shows 8 nucleotides.


Mean mark 56%.

BIOLOGY, M5 2022 HSC 12 MC

The following diagram represents a short section of DNA.
 

What are the components labelled and ?
 

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Show Worked Solution

→ is a pentagon therefore representing a five-carbon sugar.

→ is connecting the sugars in the DNA backbone and therefore must be a phosphate group.

→ As is part of the bond between Adenosine and Thymine because the bond only contains 2 hydrogen bonds, and that Cytosine only bonds with Guanine, must be Thymine.


♦♦ Mean mark 34%.

BIOLOGY, M5 2020 HSC 16 MC

Analysis of DNA shows that adenine and guanine always make up 50% of the total amount of nitrogenous bases in DNA.

Which structural feature of DNA does this provide evidence for?

  1. DNA is helical in structure.
  2. DNA is always a double-stranded molecule.
  3. DNA always has adenine paired with guanine.
  4. DNA is made up of equal amounts of nitrogenous bases.
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Show Worked Solution

→ In DNA, adenine always pairs with thymine and guanine always pairs with cytosine.

→ The fact that adenine and guanine make up 50% of the total nitrogenous bases in DNA is therefore evidence that DNA is double stranded (held together by paired bases).

♦ Mean mark 27%.