Reproduction (AQA GCSE Biology)

Exam Questions

2 hours15 questions
1a5 marks

Mitosis and meiosis are two types of cell division. 

Complete Table 1 by identifying whether the statements in the table are describing mitosis or meiosis.

The first one has been done for you. 

Table 1

 

Mitosis or meiosis?

How gametes are made

Meiosis

Produces four daughter cells

 

How fertilised egg cells divide

 

Daughter cells contain half the number of chromosomes as the parent cell

 

Occurs during asexual reproduction

 

Required for growth

 

1b1 mark

In humans the gametes are egg and sperm cells. 

How many chromosomes are contained in a human gamete?

  • 46

  • 48

  • 24

  • 23

1c1 mark

When the gametes fuse together at fertilisation, the new cell that is produced is genetically different to each of the parents' cells. 

What is the new cell called? 

1d2 marks

Identical twins come from one fertilised egg splitting into two embryos. This means that they have the same DNA as each other. 

Although they are genetically identical, identical twins don't often look the same as each other. 

Why is this the case?

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2a1 mark

In 1953, scientists Watson and Crick published their work on the structure of DNA. 

What term is used to describe the shape of DNA? 

2b3 marks

DNA is made from a series of nucleotides bonded together.

Figure 1 shows a nucleotide.

Label Figure 1 with the names of the parts of the nucleotide.  

Figure 1

nucleotide-labelling-1
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2 marks

The DNA in one human body cell is made up of 6 000 million nucleotides.

Each nucleotide is 0.34 nanometres (nm) long.

Calculate the length of the DNA in the cell in millions of nanometres.

2d5 marks

Higher Tier Only

Complete the sentences by picking one of the words in each set of [ ] brackets. 

A section of DNA that codes for a protein is called a [gene / base / chromosome].

Within that section of DNA there are four bases; A pairs with [G / T] and C pairs with [G / T].

Each series of [2 / 3 / 4] of these bases code for one [sugar / fatty acid / amino acid]. These combine together to form a protein. 

If the DNA code changes this is called a [change / mutation / genotype] and can result in a different protein being made. 

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3a1 mark

Haemochromatosis is an inherited condition where iron levels in the blood slowly build up and can cause damage to organs if left untreated. It is caused by a recessive allele. 

What is the definition of the word allele?

3b3 marks

Two parents without haemochromatosis decide to have children.

Complete the genetic diagram in Figure 2.

  • Identify any children with haemochromatosis.

  • Give the probability of any children having haemochromatosis.

The following symbols have been used:

H = dominant allele

h = recessive allele

Figure 2

punnett-square-3
3c1 mark

What is the genotype of each of the parents?

Pick one option:

  • Homozygous dominant

    • Heterozygous

    • Homozygous recessive

3d
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2 marks

Using your answer to part b, calculate the probability that the couple's next child will be a girl with haemochromatosis. 

Use the equation:

Probability of a girl with haemochromatosis = probability of haemochromatosis x probability of being a girl

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4a1 mark

The genetic disorder Down's syndrome is a condition caused by a change in the chromosomes.

Figure 3 shows the chromosomes from one cell of a person with Down's syndrome.

Figure 3

down-syndrome-karyotype-1

How does Figure 3 show that this person is female?

4b2 marks

Describe how the chromosomes shown in Figure 3 are different from the chromosomes of a person who does not have Down's syndrome. 

4c1 mark

As a woman gets older the chance of her having a baby with Down's syndrome increases.

Figure 4 shows this.

Figure 4

genetic-disorder-graph-1

The chance of a 25-year-old woman having a baby with Down's syndrome is 1 per 1000 births.

What is the chance of a 40-year-old woman having a baby with Down's syndrome?

4d3 marks

Some older mothers may choose to undergo embryo screening.

(i) What is embryo screening?

[1]

(ii) Why do some people disagree with the practice of embryo screening for pregnant women?

[2]

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5a1 mark

Higher Tier Only

Figure 5 shows a single strand of DNA with the bases labelled. 

Figure 5

dna-strand-1

Write the sequence of DNA bases that would be found on the opposite strand to the one shown in Figure 5

5b1 mark

Higher Tier Only

How many amino acids does the DNA strand in Figure 5 code for? 

5c3 marks

Higher Tier Only

Determine the correct order of the statements below to describe how the strand in Figure 5 goes from a DNA code to a functioning protein.

A

When the protein chain is complete it folds up to form a unique shape.

B

A template copy of the DNA strand is made.

C

Carrier molecules bring the amino acids to the ribosome to add to the growing protein chain.

D

Each amino acid is specific and matches the triplet code on the template to ensure they are in the correct order.

5d3 marks

Higher Tier Only

Describe how a mutation in a gene might result in a non-functioning enzyme. 

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1a2 marks

A child took a bite of a strawberry bought at a food market.

The child thought the strawberry tasted so good, she decided she wanted to grow her own strawberry plants from the remaining seeds from the strawberry.

She let the seeds germinate before planting them in her parent’s allotment.

The following summer, the plants grown from the seeds produced strawberries.

The child was disappointed that the strawberries grown in the allotment were not as large and didn’t taste the same as the strawberry from the market.

Explain why the strawberries grown by the child did not have the same characteristics as the market bought fruit.

1b2 marks

Strawberries can naturally reproduce asexually by producing runners.

How does asexual reproduction differ from sexual reproduction?

1c3 marks

Farmers can use an alternative method to produce strawberry plants that taste the same as the strawberries from a parent plant.

Explain how farmers can produce strawberries that are identical to the parent plant.

1d2 marks

Describe how the cells formed by meiosis and mitosis differ from each other.

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2a3 marks

The skin is the largest organ of the human body.

Every 30 minutes, 0.03 g of skin is lost. 

Calculate how many kg of skin is lost by the average human in 365 days.

Write your answer in standard form.

2b1 mark

Name the type of cell division that occurs in the skin to replace those cells that are lost.

2c3 marks

In the average adult human male, sperm are continually produced in the testicles by a process known as spermatogenesis.

Every second, around 1500 new sperm cells are made.

Calculate how many sperm cells are produced by an average adult male in 365 days.

Write your answer in standard form.

2d6 marks

Compare the type of cell division that occurs in the testes with that that occurs in the skin.

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3a3 marks

Tay-Sachs disease is an inherited genetic disorder that results in the destruction of neurones in the brain and spinal cord.

Babies born with Tay-Sachs disease typically do not survive into childhood.

Two parents who do not have Tay-Sachs can still produce children who do have the disease.

Explain how children can inherit this disease from parents who are symptomless.

3b3 marks

Tay-Sachs is more prevalent in certain communities.

A genetic test can reveal if a person carries the allele for Tay-Sachs.

A couple wish to have a child but they are both carriers of Tay-Sachs.

Suggest how modern technology could help the couple have a child without Tay-Sachs disease.

3c1 mark

Many people object to using reproductive technology to help couples have children with or without certain characteristics.

Suggest one reason it might be considered acceptable to use technology to help a couple have a child that does not have a genetic disorder like Tay-Sachs.

3d1 mark

At the moment it is not acceptable to use reproductive technology to allow a couple to select the gender of their offspring.

Suggest one reason why.

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4a2 marks

Daffodils are one of the most recognisable plants in the UK.

They typically grow in winter and bloom in early spring, with distinctive yellow flowers.

Daffodils can reproduce asexually by making bulbs.

One advantage of reproducing asexually is that it is faster and more energy efficient.

Suggest two other advantages of asexual reproduction for daffodils.

4b4 marks

Despite the fact that they can reproduce asexually, daffodils can also reproduce sexually.

Explain why it may also be advantageous for daffodils to also be able to reproduce sexually.

4c2 marks

There are two types of cell division; mitosis and meiosis.

Explain why meiosis is not necessary in asexual reproduction.

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5a1 mark

DNA is a polymer made from four different nucleotides.

Figure 1 shows a molecule of DNA with the four bases represented by the letter A, B, C and D.

Figure 1

hypothetical-gene

What are the components of a nucleotide?

5b5 marks

Higher Tier Only

The chain of bases shown in Figure 1 act as a 'hypothetical' gene for the synthesis of a protein, haemoglobin.

Describe how this chain of bases leads to the production of haemoglobin in the cell.

5c1 mark

Higher Tier Only

DNA can make copies of itself in a process known as replication.

What property of DNA allows it to replicate itself?

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1a2 marks

Figure 1 shows the life cycle of a fungus. 

n represents the number of chromosomes. 

Figure 1

fungi-life-cyle-1

Using Figure 1, name process A and process B. 

1b2 marks

Compare the genetic composition of the spores that are produced after process A and process B to each other, and also to the parent cells. 

1c3 marks

Explain why it is an advantage for the fungi to be able to carry out both sexual and asexual reproduction. 

1d5 marks

Compare the process shown in Figure 1 to the process used when strawberry plants reproduce. 

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2a3 marks

The Human Genome Project was a scientific endeavour to work out the sequence of base pairs in the entire human genome. 

The project was a collaborative effort involving scientists from all over the world. 

It ran from 1990 to 2003 and cost around $2.7 billion.

More than three billion base pairs were identified during the project. 

Explain why it is important for humans to understand the human genome. 

2b1 mark

Since the original project, thousands of other DNA sequences have been recorded from a wide range of different people.

In early 2022 the world record for the fastest whole human genome sequencing was achieved. 

Scientists from Stanford University sequenced the whole human genome in 5 hours and 2 minutes. 

Why is it beneficial to collect the data as quickly as possible?

2c3 marks

As well as humans, scientists have sequenced the whole genome, or small sections of DNA, from thousands of different non-human species, such as bacteria, animals and plants. 

Explain why it is important to sequence the DNA of non-human species. 

2d
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5 marks

The length of a DNA double helix increases by 0.34 nm for every pair of nucleotides.

The total number of nucleotides in a human body cell is 1.2 × 1010.

Calculate the total length of double helix in a human body cell.

Give your answer in metres.

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3a
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2 marks

Higher Tier Only

In a sequence of DNA there are sections of coding DNA called genes, and sections of non-coding DNA. 

Scientists believe that, of all the DNA in the human genome, less than 2 % codes for proteins. 

There are 3 x 109 base pairs in the human genome.

Calculate how many of these code for proteins.

Give your answer in standard form.

3b1 mark

Higher Tier Only

A strand of DNA is shown in Figure 2.

Figure 2

dna-before-mutation-graphic-1

Table 1

DNA sequence

Amino acid

TAC

Met

CAT

Val

GTA

His

GGT

Pro

AGG

Ser

CTT, CTC

Glu

CTA

Asp

ATG

Tyr

Use the information in Table 1 to determine the sequence of amino acids coded for by the DNA strand in Figure 2.

3c3 marks

Higher Tier Only

A mutation occurs which causes a T nucleotide to be inserted into the DNA strand.

Strand 2 in Figure 3 shows how the DNA code changes after the mutation. 

Figure 3

mutation-graphic-2

Using Table 1 and your own knowledge, describe how the mutation will change the protein coded for by this section of DNA. 

3d2 marks

Higher Tier Only

If a person possesses this mutation in their DNA, why might it be the case that their phenotype does not change as a result?

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4a3 marks

Cystic fibrosis is an inherited condition. 

A cystic fibrosis sufferer's mucus becomes thick in their breathing system.

Figure 4 shows how, in a healthy person, cells at the lung surface move chloride ions into the mucus surrounding the air passages.

Figure 4

mucus-in-the-lungs-1

The movement of chloride ions causes water to pass out of the cells into the mucus.

Explain why.

4b3 marks

Higher Tier Only

In a healthy person chloride ions are moved by the action of a protein channel. In a person with cystic fibrosis the protein channel does not function and the ions are not moved. 

Explain how non-functioning proteins occur inside cells. 

4c2 marks

Figure 5 shows the inheritance of cystic fibrosis in one family.

Figure 5

pedigree-chart-example-1

Suggest whether cystic fibrosis is caused by a dominant or recessive allele.

Use evidence from Figure 5 to support your answer. 

4d5 marks

Couple 5 and 6 from Figure 5 are Mr and Mrs Brown. 

Mr and Mrs Brown are hoping to have another child but are worried about the chance that the future child will have cystic fibrosis. 

They decided to visit a genetic counsellor who discussed embryo screening.

Read the information which they received from the genetic counsellor.

  • Five eggs will be removed from Mrs Brown's ovaries while she is under an anaesthetic.

  • The eggs will be fertilised in a dish using Mr Brown’s sperm cells.

  • The embryos will be grown in the dish until each embryo has about thirty cells.

  • One cell will be removed from each embryo and tested for cystic fibrosis.

  • A suitable embryo will be placed into Mrs Brown’s uterus and she may become pregnant.

  • Any unsuitable embryos will be destroyed.

Using your knowledge of cystic fibrosis and the information above, evaluate the use of embryo screening in this case.

Give a conclusion to your evaluation.

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5a2 marks

Red-green colour blindness is a genetically inherited condition that causes individuals with the condition to not be able to distinguish between certain colours. 

Red-green colour blindness is caused by a recessive allele located on the X chromosome. 

In order for a male to have the condition they only need to inherit one copy of the recessive allele on the X chromosome, whereas a female needs to inherit two copies of the recessive allele. 

Why is this the case?

5b1 mark

Using Figure 6, explain why it is possible for the X chromosome to have genes that are not found on the Y chromosome. 

Figure 6

karyogram-showing-a-typical-karyotype-1
5c5 marks

Higher Tier Only

A heterozygous woman and a colour blind man want to have a child.

Draw a Punnett square diagram to determine the probability of the child having colour blindness

Identify any children with colour blindness.

Use the following symbols:

XB = dominant allele on the X chromosome

Xb = recessive allele on the X chromosome

Y = Y chromosome (no colour blindness allele)

 

Father

Mother

Parental phenotypes

_________________

_________________

Parental genotypes

_________________

_________________

Gametes

________  ________

________  ________

Offspring genotypes: _____________________________________________

Offspring phenotypes: ____________________________________________

5d
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4 marks

In humans 8 % of males and 0.6 % of females of Northern European ancestry suffer from red-green colour blindness. 

A sample of people with Northern European ancestry was surveyed; the sample included 5 000 000 males and 5 000 000 females.

Calculate how many more men from this sample suffer from red-green colour blindness than women. Give your answer in standard form.

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