11 mark
Carrots have different physical characteristics such as colour.
Which genetic term describes the physical characteristics of a carrot?
| ☐ | A | genotype | |
| ☐ | B | monohybrid | |
| ☐ | C | phenotype | |
| ☐ | D | heterozygous |
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3.2 Inheritance
2a
2 marks
2 marksFigure 1 shows a pea plant with flowers.
(i)
Figure 1
Name the type of reproduction involving flowers.
(1)
(ii)
What is the advantage of reproduction involving flowers?
(1)
| ☐ | A | all the offspring are identical | |
| ☐ | B | there is variation in the offspring | |
| ☐ | C | there is no fertilisation | |
| ☐ | D | all the offspring grow faster |
2b3 marks
3 marksThe seeds produced by this pea plant can be round or wrinkled.
The allele for round seeds (R) is dominant to the allele for wrinkled seeds (r).
(i)
A homozygous dominant round seeded plant was crossed with a homozygous recessive wrinkled seeded plant.
Complete the Punnett square to show the genotypes of the offspring.
(1)
| r | r | |
| R | ||
| R |
(ii)
State the percentage of the offspring that will produce round seeds.
(1)
(iii)
Which scientist discovered the basis of genetic inheritance by crossing pea plants?
(1)
| ☐ | A | Charles Darwin | |
| ☐ | B | Alfred Wallace | |
| ☐ | C | Louis Leakey | |
| ☐ | D | Gregor Mendel |
2c2 marks
2 marksThe blood group of a person is determined by their genotype.
Describe how a person inherits the blood group AB.
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3a1 mark
1 markGregor Mendel was an Austrian monk who studied inheritance. In one of his investigations, Mendel looked at inheritance of seed colour in sweet peas.
The pea pod colours are controlled by a single gene with two alleles. The resulting phenotypes were either pea plants with yellow seeds or pea plants with green seeds.
Define the term allele.
3b1 mark
1 markThe image below shows one of the crosses carried out by Gregor Mendel in which a homozygous plant with yellow seeds was crossed with a homozygous plant with green seeds. All of the offspring had yellow seeds.
Using the information in the diagram, state which allele of the seed colour gene is dominant.
3c3 marks
3 marksTwo heterozygous pea plants with yellow seeds were crossed as shown in the diagram above to produce the F2 generation.
(i)
Complete the Punnet square to show the genotypes that are produced in this cross.
| Yy | |||
| ............ | ............ | ||
| Yy | Y | ............ | ............ |
| y | ............ | ............ | |
(2)
(ii)
State the phenotypic ratio produced in this cross.
(1)
3d1 mark
1 markSeed colour in sweet peas is a trait determined by a single gene.
Give the term used to describe a trait which is determined by multiple genes.
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4a2 marks
2 marksThe graph shows the different blood groups of patients recorded in a hospital.
(i)
State the type of variation shown in the graph.
(1)
(ii)
Explain your answer to part (i).
(1)
4b4 marks
4 marksThe table shows different examples of variation.
Tick all the boxes that show examples of continuous variation.
| Arm length | |
| Skin colour | |
| Eye colour | |
| Height | |
| Tongue rolling | |
| Weight |
4c3 marks
3 marksVariation can be caused by mutation.
(i)
What is a mutation?
(1)
| ☐ | A | The process of taking genes from the DNA of one organism and inserting them into the DNA of another | |
| ☐ | B | The cause of continuous phenotypic variation in organisms | |
| ☐ | C | Incorrectly formed proteins which are non-functional | |
| ☐ | D | A random change in the nucleotide base sequence of DNA |
(ii)
Random mutations in the DNA of pathogenic bacteria is a global concern due to the risks for patients having treatment in hospital.
Give the reason that mutations in bacterial DNA is of particular concern.
(2)
4d4 marks
4 marksThe following is a passage relating to variation with some missing words.
In addition to new alleles which form as a result of mutation, variation is introduced into populations through other mechanisms.
The process of ___________ creates genetic variation between gametes of an individual.
Random fusion of gametes at _____________ leads to genetic variation between _______.
Phenotype is also influenced by _____________ factors such as climate, diet or lifestyle.
Complete the above sentences, using the words from the box below. You can use each word once, more than once or not at all.
| zygotes | fertilisation | genetic | meiosis |
| environmental | mitosis | gametes | embryos |
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5a2 marks
2 marksDefine the term "monohybrid inheritance" and provide an example.
5b2 marks
2 marksState the significance of a horizontal line between a male and female symbol in a family pedigree chart.
5c1 mark
1 markSelect the option that correctly identifies a limitation of Mendel's experiments.
| ☐ | A | Mendel lacked mathematical skills, affecting data analysis | |
| ☐ | B | Mendel didn't consider the role of environment in trait expression | |
| ☐ | C | Mendel's experiments were conducted exclusively on animals, limiting applicability | |
| ☐ | D | Mendel failed to recognize the significance of dominant alleles in his findings |
5d6 marks
6 marksTable 1 below shows a Punett square for a cross between a heterozygous tall pea plant and a homozygous recessive short pea plant.
(i)
Fill the table knowing that:
“T” represents the allele for tall plants (dominant).
“t” represents the allele for short plants (recessive).
“T” represents the allele for tall plants (dominant).
“t” represents the allele for short plants (recessive).
(4)
Table 1
| Punnett square | ||
(ii)
Using the Punnett square above, provide the genotypic and phenotypic ratios of the potential offspring.
(2)
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1a3 marks
3 marksA gene coding for a protein has two alleles.
Figure 1 shows the first 5 codons of an mRNA strand for these alleles.
Allele 1 – AUG CCA CAG GAG UUC
Allele 2 – AUG CCA GAG GAG UUC
Figure 1
Allele 2 has a mutation.
Figure 2 shows the key needed to predict the translated amino acid sequence of the protein.
| codon | AUG | CCA | CAG | GAG | UUC |
| amino acid | Met | Pro | Gln | Glu | Phe |
Figure 2
Explain how the mutation in allele 2 could affect the functioning of this protein.
1b6 marks
6 marksThe inheritance of different alleles affects the phenotype of an individual.
A child is blood group O.
The child’s mother is blood group A and the child’s father is blood group B.
Explain how this child is blood group O.
Use the Punnett square and probability in your answer.
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2a3 marks
Higher Tier Only
One gene can have several different alleles.
Explain why these alleles can produce proteins with different structures.
2b4 marks
Higher Tier Content only
Monoclonal antibodies are proteins.
Figure 1 shows the process of monoclonal antibody production.
Figure 1
(i)
Which type of cell is added to the B lymphocytes to produce the hybridoma?
(1)
| ☐ | A | phagocytic cell | |
| ☐ | B | red blood cell | |
| ☐ | C | cancer cell | |
| ☐ | D | epithelial cell |
(ii)
A person with blood group A has the A antigen on the surface of their red blood cells.
Monoclonal antibodies can be used to detect the A antigen on red blood cells to determine the blood group of a person.
Explain why monoclonal antibodies, used to detect blood group A, would not react with the blood of a person with blood group B.
(3)
2c5 marks
The allele for blood group A and the allele for blood group B are codominant.
Gregor Mendel investigated the inheritance of alleles using flowering plants.
He showed that the allele for red flowers (IR) is codominant with the allele for white flowers (IW).
A heterozygous plant produces pink flowers.
(i)
Give the genotype for a plant producing white flowers.
(1)
(ii)
Explain the outcome if two plants that produce pink flowers are crossed.
You should complete the Punnett square as part of your answer.
(4)
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3a2 marks
2 marksBaldness is a sex-linked inherited disorder that affects around 70% of the male population.
However, only around 40% of women are affected by baldness.
Explain why more men than women are affected by baldness.
3b4 marks
4 marksBaldness is caused by the dominant allele, B. Non-baldness is caused by the recessive allele, b.
Complete the Punnett square to show the outcome of a cross between a heterozygous female and an unaffected male.
Show the percentage probability of a male offspring being affected by baldness in your answer.
Percentage probability of male offspring affected by baldness ……………………… %
3c2 marks
2 marksThe pedigree diagram in Figure 1 shows the baldness pattern across four generations of one family.
Figure 1
(i)
Give the genotype of person 1 in Figure 1.
(1)
(ii)
Suggest how you can tell from the pedigree diagram in Figure 1 that baldness is caused by a dominant allele.
(1)
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4a5 marks
5 marksThe alleles for fur colour in cats are codominant.
It has been found that the allele for ginger fur (CG) is codominant with the allele for black fur (CB). A heterozygous cat has tortoiseshell-coloured fur.
(i)
Give the genotype for a cat with ginger fur.
(1)
(ii)
Explain the outcome if two cats with tortoiseshell fur are crossed.
You should complete the Punnett square as part of your answer.
You should complete the Punnett square as part of your answer.
(4)
4b2 marks
2 marksSickle cell anaemia is another example of an inherited disorder whereby the alleles that cause it are codominant.
Sickle cell anaemia affects the shape of red blood cells, causing them to be shaped like sickles or crescent moons rather than their regular round shape. This means they can become rigid or sticky, which can slow blood flow. These red blood cells die much quicker than regular-shaped red blood cells.
Suggest why someone with sickle cell anaemia feel fatigued much more quickly than someone without sickle cell anaemia.
4c3 marks
3 marksFigure 1 shows the inheritance of sickle cell anaemia in a family.
Figure 1
(i)
Sickle cell anaemia is caused by a recessive allele (b).
Explain how it is possible to tell this from Figure 1.
Explain how it is possible to tell this from Figure 1.
(1)
(ii)
A blood test shows that person 10 is a carrier for sickle cell anaemia.
Person 10 has recently married an unaffected male who is also a carrier for sickle cell anaemia.
What is the probability that their first child will have sickle cell anaemia?
(1)
(iii)
Suggest the genotype of person 6 in Figure 1.
(1)
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5a3 marks
3 marksTay-Sachs is a rare inherited disorder that stops nerves from working properly and often leads to progressive damage to and the death of cells due to a build up.of a lipid called GM2 ganglioside
In unaffected individuals, an enzyme called β-hexosaminidase A helps to break down GM2 ganglioside.
Explain how a change in one amino acid in β-hexosaminidase A could stop the enzyme working properly.
5b5 marks
5 marksTay-Sachs is caused by a recessive allele.
The diagram in Figure 1 shows the inheritance pattern for Tay-Sachs in a family.
Figure 1
(i)
State the genotypes and phenotypes of individuals 8 and 2.
Use T for the normal allele and t for Tay-Sachs disease.
Use T for the normal allele and t for Tay-Sachs disease.
(2)
(ii)
Explain your choice of genotype for individual 2.
(3)
5c2 marks
2 marksAnother genetic disorder, called Duchenne Muscular Dystrophy (DMD), is a progressive condition that gradually causes muscles to weaken. It is caused by a mutation in a gene.
About 1 in 3600 men suffer with DMD, but only 1 in 50,000 women have the genetic condition.
Explain why more men than women suffer with DMD.
5d6 marks
6 marksThere are few known cures for DMD, but one type of treatment currently being researched is the use of stem cell therapy. This involves using stem cells from the patient to make healthy muscle cells, which could then be used to replace the damaged ones that cause DMD. The new muscle cells have a low risk of being rejected by the patient however the gene mutation may still affect some of these stem cells.
The graph in Figure 2 shows how patients categorised their DMD symptoms following treatment by stem cell therapy.
Figure 2
(i)
Calculate the percentage decrease between patients who felt a mild improvement and patients who felt a significant improvement in their symptoms.
Give your answer to 2 decimal places.
Give your answer to 2 decimal places.
(2)
(ii)
A student concluded that individuals who have DMD should use tried and tested treatments such as hormone therapy and have physiotherapy instead of receiving stem cell therapy.
Evaluate this conclusion. Use your knowledge of using adult stem cells in medicine in your answer.
Evaluate this conclusion. Use your knowledge of using adult stem cells in medicine in your answer.
(4)
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1a1 mark
1 markGregor Mendel carried out hundreds of breeding experiments with pea plants.
State what Gregor Mendel was able to show.
1b3 marks
3 marksIn one of Mendel's experiments using pea plants, he crossed a tall plant with a small plant.
The offspring plants in this first generation were all tall.
Mendel then crossed two tall plants from the first generation to produce new offspring plants (second generation).
Explain how the second generation plants led Mendel to conclude that there were two factors (alleles) that controlled height in pea plants with one being dominant over the other.
1c3 marks
3 marksExplain why Mendel's work was not recognised until after his death.
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2a5 marks
5 marksFigure 1 shows a list of key terms and definitions relating to inheritance but they are in the incorrect order.
| Key term | Definition |
| 1. Heterozygous | A. Different versions of a particular gene |
| 2. Gene | B. When two alleles of a gene are the same |
| 3. Homozygous | C. An allele that expresses its phenotype even if only one copy is present |
| 4. Recessive | D. Short lengths of DNA found on a chromosome that codes for a protein |
| 5. Allele | E. When two alleles of a gene are different |
| 6. Dominant | F. An allele whose phenotype is masked unless both copies are present |
Figure 1
(i)
Match the correct key term with the corresponding definition.
(3)
(ii)
Describe the difference between genotype and phenotype.
(2)
2b5 marks
5 marksIn humans, ear wax type has two distinct types, sticky and dry. Ear wax is an inherited trait which is controlled by a single gene. The allele for sticky ear wax (E) is dominant over the allele for dry earwax (e).
(i)
A male parent with the genotype (Ee) has sticky ear wax and a female parent has dry earwax.
State the genotype of the female parent.
(1)
(ii)
Draw a Punnett square to show the possible genotypes of the offspring.
(2)
(iii)
State what the ratio of phenotypes would be for the offspring.
(2)
2c7 marks
7 marks(i)
Explain how inheritance of biological sex is determined in humans.
(4)
(ii)
Figure 2 shows a genetic diagram.
Complete the genetic diagram to show the genotypes of the parents and any offspring
(3)
Figure 2
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3a3 marks
3 marksHuman red blood cells can be categorised into different blood groups ABO.
The gene controlling human ABO blood groups has three alleles (IA, IB and Io), not just two.
Figure 1 shows all the genotypes for all the possible blood groups.
| Blood Group (Phenotype) | Genotype |
| A | IAIA IAIo |
| B | IBIB IBIo |
| AB | IAIB |
| O | IoIo |
Figure 1
(i)
Explain why the AB blood group in humans shows codominance.
(2)
(ii)
State the genetic term that describes the genotype for blood group O.
(1)
3b3 marks
3 marksHigher Tier Only
Red-green colour blindness is a sex-linked disorder as the allele for colour blindness is found on the X chromosome.
Approximately 8% of men suffer from red-green colour blindness as opposed to only 0.5% of women.
Suggest why red-green colour blindness is less prevalent in women.
3c5 marks
5 marksHigher Tier Only
The following symbols can be used to represent the alleles for red-green colour blindness:
XB = an X chromosome carrying the normal allele for colour vision
Xb = an X chromosome carrying the allele for colour blindness
Y = the Y chromosome does not have an allele for this gene
The genotypes for red-green colour blindness of a mother and father are shown in Figure 2.
Figure 2
(i)
State what the phenotypes of the parents are.
(2)
(ii)
Complete the Punnett square to show the possible genotypes of any female or male offspring.
(2)
(iii)
If these parents have a child, state the probability that the child will be red-green colour blind.
(1)
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4a2 marks
2 marks(i)
Describe what the term 'variation' means in the context of a population.
(1)
(ii)
State why the following phrase is incorrect.
"Variation between individuals within populations is only caused by a variation in their genes"
(1)
4b9 marks
9 marksVariation in organisms can be caused by genetic and environment factors or a combination of both.
Figure 1 shows a list of characteristics in humans.
| Characteristic | Genetic | Environment | Both |
| 1. Blood type | |||
| 2. Eye colour | |||
| 3. Scar | |||
| 4. Skin colour | |||
| 5. Weight | |||
| 6. Inherited diseases |
Figure 1
(i)
Complete Figure 1, placing a tick (✓) in the appropriate column for each example characteristic.
(3)
(ii)
Give an explanation for each of your answers in Figure 1.
(6)
4c6 marks
6 marksDescribe the differences between continuous variation and discontinuous variation.
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5a2 marks
2 marksThe Human Genome Project was an international scientific research project to determine the sequence of all the bases that make up human DNA and to identify and map all of the genes.
State two potential applications of the Human Genome Project within medicine.
5b3 marks
3 marks(i)
There is usually extensive genetic variation within a population of a species due to variations in alleles.
State how this variation arises.
(1)
(ii)
State two factors that can lead to changes in the base sequence of DNA.
(2)
5c1 mark
1 markMost mutations don't significantly affect the phenotype.
Explain why this is.
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6a4 marks
4 marksMendel’s research on pea plants showed that genetic traits are inherited.
(i)
Which term is used to describe the expression of traits in an organism?
(1)
| ☐ | A | genotype | |
| ☐ | B | phenotype | |
| ☐ | C | allele | |
| ☐ | D | gamete |
(ii)
Mendel crossed pea plants that produced round seeds with pea plants that produced wrinkled seeds.
All the offspring produced round seeds.
He then crossed these offspring with each other.
Some pea plants in the next generation produced round seeds and the others produced wrinkled seeds.
Explain how this showed that some inherited traits are not expressed in an organism.
(3)
6b3 marks
3 marksHigher tier content only
Duchenne muscular dystrophy is a recessive sex-linked genetic disorder.
This disorder causes muscle weakness.
Figure 1 shows the inheritance of Duchenne muscular dystrophy in a family.
Figure 1
State and explain the phenotype of person Z.
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7a5 marks
5 marksGregor Mendel investigated genetic inheritance using pea plants.
Figure 1 shows some of the equipment used in this investigation.
Figure 1
(i)
Gregor Mendel crossed red-flowered pea plants with white-flowered pea plants.
Describe how this equipment could be used to do this cross and discover the flower colour of the new pea plants produced.
(3)
(ii)
Describe how to make sure that the results obtained from this investigation are not anomalous.
(2)
7b2 marks
2 marksIn a different investigation, Mendel crossed pea plants that produced yellow seeds (AA) with pea plants that produced green seeds (aa).
The dominant allele is shown as A.
The Punnett square shows the genotypes of the offspring from this cross.
| A | A | |
| a | Aa | Aa |
| a | Aa | Aa |
Explain a conclusion that can be made from the results of this cross.
7c1 mark
1 markMendel did his investigations in the 19th century.
State one reason why Mendel could not fully explain the results of his investigations.
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85 marks
Haemochromatosis is a disease that occurs when iron accumulates in the liver.
A person with haemochromatosis is treated by having 0.5 dm3 of their blood removed each week.
This lowers the level of iron in their blood.
(i)
Give two safety precautions needed when blood is removed from this person.
(2)
(ii)
Haemochromatosis can be inherited.
Haemochromatosis occurs when a person inherits two copies of a recessive allele.
Figure 1 shows the inheritance of haemochromatosis in a family.
Figure 1
State and explain the genotype of female Z.
(3)
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94 marks
Sickle cell disease is a recessive genetic disorder in humans.
(i)
Two parents are heterozygous for sickle cell disease.
Complete the Punnett square to show the possible genotypes of their children.
(1)
| D | d | |
| D | ||
| d |
(ii)
State the percentage probability that their children could have sickle cell disease.
(1)
(iii)
A father with the genotype dd and a mother with the genotype DD plan to have several children.
Explain why none of their children will have sickle cell disease.
(2)
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106 marks
6 marksA karyogram is a picture of the chromosomes found in the nucleus of a single cell.
Figure 1 shows a human karyogram.
Figure 1
(i)
State two reasons why this karyogram cannot be from a gamete (sex cell).
(2)
(ii)
State the gender shown by this karyogram.
(1)
(iii)
Complete the Punnett square to show how gender is inherited.
(2)
| male gametes | |||
| female gametes |
|||
(iv)
State the probability that a child will be male.
(1)
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