Patterns of Inheritance (OCR A Level Biology)

Scientists self-pollinated some pea plants that were heterozygous for the gene controlling height.

They expected a 3:1 ratio of tall plants to short plants in the offspring.

1046 plants grew in the next generation. 798 were tall and 248 were short.

Which of the following, A to D, is a statistical test that could be used to determine if these numbers are significantly different from a 3:1 ratio?

Which of the following is not associated with the use of artificial selection in farm animals?

The ability to roll one’s tongue is under the control of a single gene. The gene has two alleles R and r.

People who can roll their tongues can have the genotypes RR or Rr. People who cannot roll their tongues have the genotype rr.

A survey by a student showed that 12% of the population in a single school cannot roll their tongues.

The student then used the Hardy-Weinberg principle to calculate the number of heterozygous individuals in the school.

Which of the following represents the percentage of heterozygous individuals at the student’s school?

Use the equations: p + q = 1 and p² +2pq + q² = 1

Selection pressure can affect homozygous individuals. The effect can be investigated using a model gene pool.

A large gene pool is necessary to ensure that

In a breeding experiment, a tall, round seeded (homozygous dominant) pea plant was crossed with a short, wrinkled seeded (homozygous recessive) pea plant. The F₁ dihybrid plants were then used in a test cross.

If the genes are always linked and no crossing over occurs, what would be the predicted ratio in the F₂ generation?

In a variety of roses, P is the allele for pink petal colour and D is the allele for double flower. The genes are not linked.

Which cross will give a 1:1:1:1 ratio of phenotypes in the offspring?

Long hair in a species of rabbit is caused by the presence of the allele H^L. These rabbits have either very long hair or moderately long hair. The 'wild-type' short-haired rabbit possesses the allele H^S.

The diagram below shows the results of two crosses involving one female and two male rabbits.

Use the pedigree diagram to identify which row of the table below shows the correct phenotypes for the rabbits with genotypes H^LH^L and H^LH^S

Aubergine (Solanum melongena L.) belongs to the same family as potatoes and tomatoes. 

Scientists were studying two inherited traits of the aubergine plants,

1. Prickly or non-prickly stem
2. Round or linear fruit

A pure-breeding non-prickly stemmed round fruit aubergine and a pure-breeding prickly stemmed linear fruit aubergine were crossed. All the F1 offspring were non-prickly stemmed with round fruit.

When members of the F1 generation were crossed, the F2 generation included 27 aubergine with non-prickly stems and linear fruit.

Which of the options, A to D, shows the observed results that most closely match the expected results for the number of non-prickly stemmed round fruit aubergines and prickly stemmed round fruit aubergines?

Which of the following events takes place during prophase 1 of meiosis and contributes to an increase in genetic variation? 

A number of events occur for a new species to emerge in a population.

Which of the following statements correspond to events that are involved in the formation of a new species?

Statement 1: Gene mutation

Statement 2: Selection pressure

Statement 3: A change in the environment

Statement 4: A large population size

A species of butterfly has one gene W, controlling wing spot colour and another E, controlling eye colour. 

The dominant allele, W, produces black spots while the recessive allele, w, produces grey spots. 

The dominant allele, E, produces black eyes while the recessive allele, e, produces brown eyes. 

A black-spotted, brown-eyed butterfly is crossed with a grey-spotted, black-eyed butterfly. The offspring are all black-spotted and black-eyed. 

What could potentially explain the cause of the offspring phenotype?

 A species of tropical bird has two genes involved in plumage colour, R and D. 

The dominant allele R codes for red pigment in wing feathers, while the recessive allele, r codes for yellow pigment in the wing feathers. 

The dominant allele D codes for an enzyme involved in pigment deposition, while the recessive allele d does not produce the enzyme involved in pigment deposition, resulting in white feathers.

If two double heterozygous red-winged birds breed, what will be the likely phenotypic ratio of the offspring?

 In birds, females have ZW sex chromosomes and males have ZZ sex chromosomes. A gene present on the Z chromosome, G, affects the speed of feather growth in young chickens. The dominant allele, G causes fast growth while the recessive allele, g causes slow growth. 

If a male chicken with genotype ZG Zg breeds with a female with the genotype Zg W, what will be the phenotypes of the offspring that they produce?

Which of the following statements accurately differentiate the nature of discontinuous variation from the nature of continuous variation?

A population of newts is divided into two separate populations over time by the formation of a large mountain range which the newts cannot cross. On one side of the mountain range, the temperature is cold and most of the newt’s available food is large terrestrial arthropods. On the other side of the mountain range, the temperature is warmer and the newt’s available food is largely small aquatic arthropods. 

At what point would speciation occur?