K325 / 2027

Molecular genetics

Try it without your notes

Choose an answer or explain your thinking. Then check what you understand.

Quick checks

0 answered / 0 correct. Your first try counts; you can try again any time.

Check your understanding

Which statement gives the correct relationship?

  1. Every chromosome is a single nucleotide.
  2. A gene is a section of DNA carried on a chromosome.
  3. A chromosome is a section of a gene, made of many DNA proteins.
Show the answer

A gene is a section of DNA carried on a chromosome.

Keep the molecule, a particular sequence and the organised chromosome structure distinct.

Check your understanding

Which bases sit directly opposite T G A C in the displayed order?

  1. A G T C
  2. A C T G
  3. T G A C
Show the answer

A C T G

Apply T-A, G-C, A-T and C-G at the four corresponding positions.

Check your understanding

A DNA sample contains 30% adenine. What percentage of its bases is cytosine?

  1. 20%
  2. 70%
  3. 40%
  4. 30%
Show the answer

20%

A pairs with T, so T = 30% and A + T = 60%. That leaves 40% for C and G, so C = 20%.

Check your understanding

Which chain best explains how a gene can affect enzyme activity?

  1. Every gene directly produces a whole organ.
  2. DNA base sequence specifies amino acid sequence, which affects protein shape and function.
  3. The DNA base sequence is copied straight into the enzyme, so the bases themselves form the active site.
Show the answer

DNA base sequence specifies amino acid sequence, which affects protein shape and function.

This connects inherited information to the structure and activity of the protein product.

Check your understanding

A gene has 900 bases in the coding sequence, read in groups of three. How many amino acids can it code for at most?

  1. 2700
  2. 300
  3. 450
  4. 900
Show the answer

300

Three bases code for one amino acid, so 900 / 3 = 300.

Check your understanding

What is transferred to create the intended new protein-producing ability in a transgenic recipient?

  1. A suitable DNA sequence containing the gene information.
  2. The donor's entire body and every cell structure.
  3. A dose of the finished protein, which the recipient's cells then keep making.
Show the answer

A suitable DNA sequence containing the gene information.

The recipient must also maintain and use that information appropriately to make the intended product.

Check your understanding

What is the plasmid's role in the insulin-production outline?

  1. It is the insulin protein injected directly from the culture.
  2. It carries the inserted insulin-coding sequence into bacterial cells.
  3. It turns the bacterial chromosome into human DNA, so the cell makes insulin.
Show the answer

It carries the inserted insulin-coding sequence into bacterial cells.

The plasmid is a DNA vector. The bacteria use the introduced information in the production system.

Check your understanding

Which enzyme joins the human insulin gene into a cut plasmid?

  1. DNA ligase
  2. Amylase
  3. Restriction enzyme
  4. Insulin
Show the answer

DNA ligase

Ligase joins the sugar-phosphate backbones of the gene and the plasmid.

Check your understanding

Which response best evaluates an engineered animal that produces a useful protein?

  1. All genetic engineering must have identical benefits and risks.
  2. Weigh the protein benefit against animal welfare, product safety and access, using evidence.
  3. If the animal makes more of the protein than other methods can, the application is acceptable.
Show the answer

Weigh the protein benefit against animal welfare, product safety and access, using evidence.

This examines the specific benefit and relevant affected parties instead of relying on a blanket judgement.

Explain your thinking

Write a short answer, then compare it with a sample and check for missing ideas.

Question 1 of 9

Calculate base percentages

4 marks

(a) In a sample of double-stranded DNA, 31% of the bases are adenine. Calculate the percentages of thymine, cytosine and guanine. (b) Another sample contains 26% A, 26% T, 30% C and 18% G. Could this be double-stranded DNA? Explain. (c) Draw and label one DNA nucleotide. [4]

A = T and C = G in double-stranded DNA. All four add up to 100%.

Loading saved work...

0 / 6000
Ctrl / Cmd + Enter

Use the checklist to compare your answer. This is a self-check, not an exam mark.

Keep one idea for tomorrow

Try a question again without looking at the answer. If you get stuck, revisit its lesson.

Open the chapter summary