Reproduction (AQA GCSE Biology)

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.

Strawberries can naturally reproduce asexually by producing runners.

How does asexual reproduction differ from sexual reproduction?

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.

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

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.

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

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.

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

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.

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.

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.

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.

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.

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.

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

Explain why meiosis is not necessary in asexual reproduction.

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

What are the components of a nucleotide?

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.

Higher Tier Only

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

What property of DNA allows it to replicate itself?

Figure 1 shows the life cycle of a fungus. 

n represents the number of chromosomes. 

Figure 1

Using Figure 1, name process A and process B. 

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. 

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

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

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. 

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?

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. 

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.

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.

Higher Tier Only

A strand of DNA is shown in Figure 2.

Figure 2

Table 1

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

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

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

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?

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

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

Explain why.

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. 

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

Figure 5

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

Use evidence from Figure 5 to support your answer. 

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.

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.

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?

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

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:

X^B = dominant allele on the X chromosome

X^b = recessive allele on the X chromosome

Y = Y chromosome (no colour blindness allele)

Offspring genotypes: _____________________________________________

Offspring phenotypes: ____________________________________________

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.