NCEA Level 1 Science 90948 (1.9) — page 1 of 4

SAMPLE ASSESSMENT SCHEDULE

Science 90948 (1.9): Demonstrate understanding of biological ideas relating to genetic variation

Assessment Criteria

Achievement Merit Excellence

Demonstrate understanding requires the student to recognise, name, draw, give characteristics of, or an account of genetic variation.

Demonstrate in-depth understanding requires the student to explain how or why genetic variation occurs.

Demonstrate comprehensive understanding requires the student to link biological ideas about genetic variation. It may involve elaborating, applying, justifying, relating, evaluating, comparing and contrasting, or analysing.

Evidence Statement

One Expected Coverage Achievement Merit Excellence

Explanation of difference:

A gene is a section of DNA that codes for a particular feature / protein.

An allele is an alternative form of the gene.

Drawing of structural relationship:

See Appendix A.

Explanation of determination of feature and variation:

Along the DNA, base sequences provide the code for building different proteins, which then determine particular features. Specific sections of the DNA determine individual features such as flower colour. Variations in the feature (eg red or white flowers) are due to (slight) differences in the sequence of the bases making up a gene. The different variations of a particular gene are called alleles and they cause the variations in the phenotypes.

TWO of:

describes either a gene OR an allele

states that a gene codes for a protein which then determines a feature

indicates that a different base sequence (alleles) results in differing plant features such as red or white flowers.

TWO of:

explains the difference between a gene and an allele in terms of how they impact on features

shows the relationship between DNA, a gene and an allele in a diagram

explains that the base sequence on a gene determines the appearance of a particular feature.

Links the explanation of the structural relationship between DNA, genes and alleles with the explanation of the production of a particular feature and variation within that feature.

Two Expected Coverage Achievement Merit Excellence

(a) Description of gametes:

A gamete is a sex cell (eg, an egg or sperm), which has half the normal number of chromosomes as body cells.

Explanation of the need for gametes:

It is required in sexual reproduction to ensure that when a sperm fuses with an egg, the resulting first cell of the new organism has the correct number of chromosomes.

THREE of:

in (a), states what a gamete is

in (a), describes relevant detail of gametes chromosome numbers

in (b), describes genetic variation

in (b), indicates that the separation of alleles/ chromosomes

TWO of:

in (a), explains why gametes are needed for sexual reproduction

in (b), explains how meiosis produces genetic variation in a population by referring to the separation of alleles which then allows new

In (b), links the explanation of why genetic variation within a population is important for the survival of the species with the explanation of how inherited variation is constantly being generated by the process of meiosis, through the reshuffling of alleles.

(b) Description of genetic variation: Genetic variation refers to a variety of different genotypes for a particular

NCEA Level 1 Science 90948 (1.9) — page 2 of 4

trait within a population.

Explanation of role of meiosis:

Meiosis produces gametes with half the number of chromosomes. This means that pairs of alleles are separated at meiosis.

At fertilisation, which sperm fertilise which egg is due to chance and this results in new combinations of alleles.

The advantage of variation to a species is that it may enable some individuals to survive if some threatening event occurs. For example, if a new disease arrives, not all individuals will be wiped out.

during meiosis results in new combinations of alleles

in (b), states that variation aids survival when conditions change.

combinations of alleles to occur at fertilisation

in (b), explains that variations in a population might allow individuals to survive in changing conditions and to pass on the ability to their offspring.

Three Expected Coverage Achievement Merit Excellence

(a) Explanation of a dominant allele:

A dominant allele is the form of a gene that is always expressed whether the individual has one or two copies of that allele.

Explanation of evidence:

A and B who both have a cleft chin produce a smooth chin child. If the cleft chin allele was recessive they would not be able to produce a child with a smooth allele, so the cleft chin allele must be dominant OR other correct evidence from chart.

THREE of:

in (a), describes what a dominant allele OR relevant punnet square linked to pedigree diagram

in (b), gives a reason for the presence of one of the alleles of the genotype

in (c), completes the Punnett Square correctly

in (c), gives the correct probabilities for cleft chin and smooth chin.

TWO of:

in (a), explains the evidence that shows that cleft chin allele is dominant

in (b), explains why individual A must have a dominant and a recessive allele using evidence from the pedigree diagram

in (c), gives the correct probabilities based on the completed Punnet square parent alleles and indicates that these can’t be used to predict what an individual will be.

In (c), links the theoretical probabilities derived from the correctly completed Punnett Square with the explanation of why the actual outcomes for families will not necessarily match the predicted outcomes, especially when dealing with small population samples.

(b) Explanation of why Dd:

As male A has a cleft chin this must mean that he carries at least one cleft chin allele (D). Male A and female B have a smooth chin boy, which means that A must have passed on a smooth chin allele (d) to the boy as to be smooth chinned the boy must have two recessive alleles, one from each parent.

(c) Punnett Square:

See Appendix B.

Calculation of probabilities:

Probability of cleft chin = ¾ or 75% or 3 out of 4

Probability of smooth chin = ¼ or 25% or 1 out of four

Explanation of discrepancy:

Random fertilisation of eggs by sperm means that number of offspring showing a particular variation will not always match the probability predicted by a Punnett square, unless the number of offspring is quite large.

NCEA Level 1 Science 90948 (1.9) — page 3 of 4

Four Expected Coverage Achievement Merit Excellence

(a) Description of a mutation:

A mutation is a change to the base sequence of a gene along the DNA of an organism or a change in the genetic code.

Explanation of inheritance:

If the mutation occurs in a gamete, then it would be inherited. As a skin cell is not a gamete, a mutation in a skin cell cannot be inherited.

TWO of:

in (a), correctly defines or describes a mutation

in (a), states that a skin cell mutation is not inheritable (or similar)

in (b), states that variation is caused by changes in genetic information (mutations)

in (b), states that plants of species A with larger leaves are better adapted to live under lower light levels OR that plants with average or small leaves will be poorly adapted to low light levels, (and will not survive for long).

TWO of:

in (a), explains why a mutation in a skin cell it not inheritable

in (b), explains what causes variation (e.g. variation in plant species A will be due to changes in genetic material)

in (b), explains how variation aids the survival of the species (eg, plant of species A have different sized leaves, and when the environment becomes more shaded some plants will be better adapted to the new conditions and therefore will survive).

In (b), links the explanation of how genetic variation arises within a plant species with the explanation of how that genetic variation aids survival of the species in a changing environment (eg, when environmental conditions are changed to lower light levels, the larger leaves of some plants of species A, means that they are better adapted to survive and reproduce, thus ensuring the survival of some individuals, and hence the species).

(b) Explanation of causes of variation: The variation in plants of species A may be due to differences (mutations) in the sequence of bases in a particular gene.

Explanation of effect of reduced light:

Those individuals of plant species A whose leaves are large will be better adapted to live under lower light levels. They will survive better and produce more offspring, increasing the number of larger leaves plants in the population.

Explanation of fate of poorly adapted plants:

Plants with average or small leaves will not be able to absorb enough sunlight and make sufficient food. In time these plants might die off.

Judgement Statement

Achievement Achievement with Merit Achievement with Excellence

Minimum of:

2A

Minimum of:

2M

Minimum of:

2E

NCEA Level 1 Science 90948 (1.9) — page 4 of 4

Appendix A

Appendix B

D d

D DD Dd

d Dd dd