Year 10 – Chapter 1.1

Question 1

Name the parts that are the building blocks of a DNA molecule.

Answer 1

The building blocks of DNA are the phosphate groups, the deoxyribose sugar and one of four different nitrogen-rich bases.

Question 2

Recall what the letters A, T, C and G represent in the context of DNA.

Answer 2

A – Adenine
T – Thymine
C – Cytosine
G – Guanine

Question 3

In the DNA molecule:

1. Recall what makes the ‘rungs’ of the ladder
2. Name the molecules that make the ‘uprights’ of the ladder
3. Recall the molecule of the ‘upright’ to which the ‘rungs’ are joined.

Answer 3

1. The base pairs make up the rungs of the ladder (I.e. A-T and C-G).
2. The molecules that make the uprights of the ladder are the phosphate groups and the sugars.
3. The rungs are joined to the sugar molecule.

Question 4

Explain why the DNA molecule is compared with a twisted ladder.

Answer 4

The DNA molecule is in a double helix shape, and this is similar to a twisted rope-ladder.

Question 5

Describe where DNA is found in an organism.

Answer 5

DNA is found in the chromosomes of a cell, which are found in the cell’s nucleus.

Question 6

Describe the relationship between DNA, chromosomes and genes in words or in pictures.

Answer 6

A gene is a section of DNA, DNA is an entire collection of genes, and chromosomes are strands of DNA that is coiled on itself.

Question 7

Explain in your own words what is meant by complementary base pairing.

Answer 7

Answer may vary, but MUST INCLUDE THE FOLLOWING:

• a base cannot pair with a similar base (Yes: A-T, No: A-A)
• bases can only pair with it’s specific partner (A-T, C-G)

Question 8

Explain in your own words what characteristic of DNA creates the genetic code.

Answer 8

Answer may vary, but MUST INCLUDE THE FOLLOWING:

• order of bases along DNA strand composes genetic code

Question 9

1. Name four scientist who contributed to our understanding of DNA.
2. Outline what each scientist did.

Answer 9

1. Any of the following: Johannes Friedrich Mescher, Pheobus Levene, Oswald Avery, Erwin Chargraff, Sir William Henry Bragg, Sir William Lawrence Bragg, Rosalind Franklin, Maurice Wilkins, James Watson, Francis Crick
2. Any of the following:
   • Johannes Friedrich Mescher: originally discovered DNA, thought it was a new chemical
   • Pheobus Levene: identified components of a nucleotide
   • Oswald Avery: found genetic code in DNA
   • Erwin Chargraff: Nucleotides arranged differently in all species, Chagraff’s rule (amounts of adenine and thymine are the same, amounts of cytosine and guanine are the same), adenine+guanine=thymine+cytosine
   • Sir William Henry and Lawrence Bragg

Question 10

State what the initials DNA represent.

Answer 10

Deoxyribonucleic acid

Question 11

Compare the amount of information that would be held in two chromosomes if one was shorter than the other.

Answer 11

There would be less genetic information in the shorter chromosome.

Question 12

Compare a gene and a chromosome.

Answer 12

A gene is a section of a DNA strand. A chromosome is a coiled strand of DNA.