Syllabus Edition
First teaching 2014
Last exams 2024
1 markTwo pea plants are heterozygous for two traits, pod and flower colour. The dominant trait for flower colour is purple and the recessive is white. The dominant trait for pod colour is green and the recessive is yellow.
If they were to breed what would the ratio of their offspring's traits be?
The ratio is as follows: purple green : purple yellow : white green : white yellow.
2 : 1 : 1 : 2
1 : 1 : 1 : 1
9 : 3 : 3 : 1
3 : 3 : 1 : 1
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In a newt, normal tail length is dominant to short tail length and green scales are dominant to white scales.
A heterozygous normal tailed newt with green scales was crossed with a short tailed newt with white scales. A large number of offspring were produced. They were either normal tailed with green scales or short tailed with white scales in equal number.
What is the most likely cause of this pattern?
The genes are codominant
Crossing over has occurred
The two genes are linked
The traits are polygenic
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Hair colour is a trait controlled by polygenic inheritance. Which statement is correct?
Hair colour shows discontinuous variation
Individuals show a wide range of phenotypes for hair colour
No two people have the same hair colour
Children always have the same hair colour as one of their parents
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A test cross resulted in these recombinants:
Which of the following was the parental test cross?
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In fruit flies (Drosophila melanogaster) brown body is dominant to black body.
If scientists want to find out the genotype of a fly with a brown body what genotype would they cross the fly with?
Homozygous recessive
Heterozygous recessive
Homozygous dominant
Heterozygous dominant
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1 markIn rabbits, brown coat is dominant to black coat and long ears are dominant to short ears. Two rabbits are heterozygous for both characteristics.
What is the probability that their first offspring will have black coats and short ears?
0
1/16
4/16
9/16
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Which of the following processes results in the production of recombinants?
I. Crossing over of bivalents
II. Independent assortment during meiosis I
III. Independent assortment during meiosis II
IV. Mutation
I only
I and II only
I, II and III only
I, II, III and IV.
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1 markThe inheritance pattern of two separate genes was investigated in a double-heterozygous cross in domestic cats (Felis catus). A chi-squared test of phenotypic ratios of the two separate genes results in a χ2 value of 7.96.
The table below shows the critical values of the chi squared distribution.
| Degrees of freedom | Probability that the difference between observed and expected results is due to chance | |||
| 0.1 | 0.05 | 0.01 | 0.001 | |
| 1 | 2.71 | 3.84 | 6.64 | 10.83 |
| 2 | 4.60 | 5.99 | 9.21 | 13.82 |
| 3 | 6.25 | 7.82 | 11.34 | 16.27 |
| 4 | 7.78 | 9.49 | 13.28 | 18.46 |
Which row of the table best describes a conclusion that can be drawn from this data?
|
Probability that the results are due to chance (High / Low) |
Are the two genes linked? (Yes/No) |
|
| A |
Low |
Yes |
| B |
Low |
No |
| C |
High |
Yes |
| D |
High |
No |
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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?
9 : 3 : 3 : 1
1 : 1 : 1 : 1
3 : 1
1 : 1
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In a variety of roses, P is the allele for pink petal colour and D is the allele for double flower.
Which cross will give a 1:1:1:1 ratio of phenotypes in the offspring?
PpDd x ppDd
PpDd x PpDd
PPdd x ppDD
Ppdd x ppDd
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If two genes are said to be linked, what is meant by the term 'linked'?
Two genes are both at the same loci on a chromosome
Two genes both occupy the same chromosome
They are both alleles of the same gene
The phenotypes of the genes are both influenced by the gender of their owner
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Fruit flies (Drosophila melanogaster) have been used in genetic cross experiments since the early 1900s. Which of the following features of fruit flies is the least good reason for choosing them for conducting genetic cross experiments?
They have a short gestation period
They reproduce in large numbers
They eat a wide variety of food
They have easily observable mutations
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Fruit flies (Drosophila melanogaster) exhibit characteristics governed by the following pairs of alleles.
M = brown body, m = black body
R = red eyes, r = white eyes
These pairs of alleles can be assumed to be unlinked.
If two double-heterozygous flies are crossed and produce 160 offspring, what is the likely number of offspring with red eyes and a black body?
90
120
30
10
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Which discovery was first made by Bateson and Punnett in the early 20th century?
Sex linkage in Drosophila melanogaster
New, as-yet-unseen alleles in sweet pea plant crosses
Chromosomes assorting independently
Non-typical ratios of offspring phenotype, at odds with Mendel's predicted ratios
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Events in meiosis play an important role in determining the inheritance of alleles. Which row of the table states the correct words to name the processes being described?
|
The orientation of chromosomes pairing up in prophase I |
Chromosome are pulled towards the poles of the cell in anaphase I |
|
| A |
Synapsis |
Assortment |
| B |
Segregation |
Assortment |
| C |
Assortment |
Segregation |
| D |
Segregation |
Cytokinesis |
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Two linked genes are denoted by the dominant alleles G and H. Their recessive counterparts are g and h respectively.
Which way of writing the allele combinations on their chromosomes best displays the linkage between the two genes?
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The inheritance pattern of two separate genes was investigated in a double-heterozygous cross in watercress plants. A chi-squared test of phenotypic ratios of the two separate genes results in a χ2 value of 3.5.
At a 5% probability level, the critical value of chi-squared is 7.8 for an experiment of this nature.
Which row of the table best describes a conclusion that can be drawn from this data?
|
Probability that the Results Are Due to Chance (High / Low) |
Are the two genes linked? (Yes/No) |
|
| A |
High |
Yes |
| B |
High |
No |
| C |
Low |
Yes |
| D |
Low |
No |
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Which row(s) below give(s) correct statements about continuous variation?
|
I. |
Most individuals are close to the mean value of a trait, with fewer individuals at the extremes |
|
II. |
There are distinct categories of the trait with no intermediate values |
|
III. |
A continuously variable trait tends to be regulated by multiple genes |
|
IV. |
Individuals are distributed approximately evenly and the environment cannot influence the trait |
I only
I, III and IV
II and IV
I and III
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Over time, many dihybrid cross experiments of autosomally-linked genes in sweet pea plants (Lathyrus odoratus) have been carried out by reputed scientists.
Which of the following best explains the presence of some non-parental phenotypes in the offspring of such crosses?
Crossing over has occurred, leading to the production of recombinant plants
The scientists made errors such as not cleaning the small paint brush that they used to transfer pollen grains between plants
Independent assortment was disproved by Thomas Hunt Morgan so unusual phenotypes are to be expected
Only plants of one gender exhibit the parental phenotypes due to linkage
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Long hair in a species of rabbit is caused by the presence of the allele HL. These rabbits have either very long hair or moderately long hair. The 'wild-type' short-haired rabbit possesses the allele HS. The diagram below shows the results of two crosses involving one female and two male rabbits. 
Which row of the table below shows the phenotypes of the rabbits with the genotypes HLHL and HLHS?
|
HLHL |
HLHS |
|
| A |
Long hair |
Moderately long hair |
| B |
Moderately long hair |
Short hair |
| C |
Moderately long hair |
Long hair |
| D |
Long hair |
Short hair |
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