Reproduction (AQA GCSE Biology: Combined Science)

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.

(a)

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.

[2 marks]

(b)

Strawberries can naturally reproduce asexually by producing runners.

How does asexual reproduction differ from sexual reproduction?

[2 marks]

(c)

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

Describe and explain how it is possible for farmers to produce strawberries that are identical to the parent plant.

[3 marks]

(d)

The type of cells formed by meiosis and mitosis differ.

Describe how.

[2 marks]

The skin is the largest organ of the human body.

Every 30 minutes, 0.03 g of skin is lost. 

(a)

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

Write your answer in standard form.

[3 marks]

(b)

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

[1 mark]

(c)

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.

[3 marks]

(d)

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

[6 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.

(a)

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.

[3 marks]

(b)

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.

[3 marks]

(c)

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 not have a child with a genetic disorder like Tay-Sachs.

[1 mark]

(d)

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.

[1 mark]

(a)

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

Explain why meiosis is not necessary in asexual reproduction.

[2 marks]

n represents the number of chromosomes. 

Figure 1

Using Figure 1, name process A and process B. 

[2 marks]

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. 

[3 marks]

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

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. 

[3 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

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

Explain why.

[3 marks]

Figure 5

Is cystic fibrosis caused by a dominant or recessive allele?

Use evidence from Figure 5 to support your answer. 

[2 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.

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.

[5 marks]

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?

[2 marks]

Higher Tier Only

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)

[5 marks]

Offspring genotypes: _____________________________________________

Offspring phenotypes: ____________________________________________

Out of a collection of 5 000 000 people from this ancestry, calculate the how many more men suffer from red-green colour blindness in comparison to women. 

Give your answer in standard form. 

[4 marks]