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BIOLOGY, M6 2024 HSC 9 MC

The diagram shows a section of a chromosome in an insect. It represents three genes amongst non-coding DNA. The crosses mark locations of four separate mutations.
 

Which location could produce a new allele for eye colour?

  1. \(P\)
  2. \(Q\)
  3. \(R\)
  4. \(S\)
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\(C\)

Show Worked Solution

→ Since \(R\) is located within the gene region for eye colour, a mutation at this location could alter the DNA sequence of this gene and produce a new allele for eye colour,.

→ Mutations at other locations (\(P, Q\) and \(S\)) are either in non-coding regions or different genes.

\(\Rightarrow C\)

BIOLOGY, M6 EQ-Bank 6 MC

An evolutionary biologist was investigating the timeframes of genetic divergence between different species of Acacia. She hypothesised that she would get a better indication of the time at which Acacia species diverged by using non-coding DNA segments rather than coding DNA segments.

Why is this hypothesis most likely to be supported by the evidence?

  1. Coding DNA segments never undergo mutation.
  2. Coding DNA segments are less stable over time due to the selection pressures of the environment.
  3. Non-coding DNA segments do not undergo mutation as they are not subject to selection pressures.
  4. Non-coding DNA segments will show greater diversity after divergence as they are not exposed to selection pressures.
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`D`

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→ Coding DNA cannot vary as much as even point mutations can be harmful or fatal.

→ Non-coding DNA does not impact the individual or their offspring and will therefore show greater variance which can be used as a tool to track species divergence.

`=>D`

BIOLOGY, M6 2019 HSC 15 MC

A germ-line mutation is known to have occurred.

How is it possible that there has been no noticeable change in the phenotype of the offspring?

  1. The mutation occurred in a stretch of RNA.
  2. The mutation occurred in a protein-coding region.
  3. The mutation occurred in a stretch of non-coding DNA.
  4. The mutation did not affect the DNA sequence of any gametes.
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`C`

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→ For the mutation to not be noticeable in the offspring, it must have occurred within junk DNA (i.e. large sections of non-coding DNA with no known purpose).

`=>C`

BIOLOGY, M6 2022 HSC 16 MC

What is the significance of mutations in non-coding DNA?

  1. They do not alter nucleotides.
  2. They do not affect phenotype.
  3. They may affect gene expression.
  4. They may alter amino acid codons.
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`C`, `B`

Show Worked Solution

→ While non-coding DNA does not directly code for polypeptides, it can be associated with inhibiting their expression.

`=>C`  (NESA solution)

→ Note that mutations in non-coding DNA can also be silent, and not have any effect on genes.

`=>B`  (Arguably alternative solution)

BIOLOGY, M6 2020 HSC 17 MC

There are about 10 million single nucleotide polymorphisms (SNPs) found in the human genome.

Four SNPs are modelled in the diagram.
 

The SNPs modelled do not affect the phenotype of the individuals shown.

Which is the best explanation for this?

  1. Only one nucleotide is different at each SNP.
  2. The SNPs are part of DNA that is not expressed.
  3. AGA, CAA, TAT and CTC all code for the same amino acid.
  4. The SNPs are present on one strand of the DNA molecule only.
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`B`

Show Worked Solution

→ Mutations that occur on non-coding DNA are not expressed as proteins.

→ Phenotype is therefore not affected.

`=>B`