Sexual & asexual reproduction

In the 19th century, Gregor Mendel studied genetic inheritance in pea plants.

Mendel made the conclusion that characteristics in organisms were determined by the inheritance of ‘units’.

What are these ‘units’ of inheritance known as today?

Figure 20 shows one of Mendel’s experiments on the inheritance of pea shape.

plants that produced plants that produced

State the conclusion that Mendel was able to make about the wrinkled pea characteristic.

A scientist crossed two pea plants that were heterozygous for pea shape.

Complete the Punnett square to show the inheritance of the alleles for pea shape and the percentage probability of producing a plant with wrinkled peas.

Use the letter R for the allele for round shape.

Use the letter r for the allele for wrinkled shape.

percentage probability of producing a plant with wrinkled peas_........

Plants used to study inheritance are grown in controlled environmental conditions.

Suggest two ways of controlling these environmental conditions.

Some plants can reproduce asexually and sexually.

Complete the table by writing yes or no in each box to show the features of asexual and sexual reproduction.

A zygote with a diploid nucleus is formed by sexual reproduction.

State what is meant by a diploid nucleus.

In the 19th century, Gregor Mendel studied genetic inheritance in pea plants.

Mendel made the conclusion that characteristics in organisms were determined by the inheritance of ‘units’.

What are these ‘units’ of inheritance known as today?

Figure 5 shows one of Mendel’s experiments on the inheritance of pea shape.

plants that produced plants that produced

State the conclusion that Mendel was able to make about the wrinkled pea characteristic.

A scientist crossed two pea plants that were heterozygous for pea shape.

Complete the Punnett square to show the inheritance of the alleles for pea shape and the percentage probability of producing a plant with wrinkled peas.

Use the letter R for the allele for round shape.

Use the letter r for the allele for wrinkled shape.

percentage probability of producing a plant with wrinkled peas_........

Plants used to study inheritance are grown in controlled environmental conditions.

Suggest two ways of controlling these environmental conditions.

Some plants can reproduce asexually and sexually.

Complete the table by writing yes or no in each box to show the features of asexual and sexual reproduction.

A zygote with a diploid nucleus is formed by sexual reproduction.

State what is meant by a diploid nucleus.

Mendel crossed pea plants that always produced purple flowers with pea plants that always produced white flowers.

The flowers of the offspring were all purple, as shown in Figure 5.

Which conclusion can be made about the characteristic for purple flowers?

Mendel used two of the offspring with purple flowers in another cross.

The pea plants he obtained from this cross produced purple flowers or white flowers in a ratio of 3: 1.

Calculate the expected number of pea plants with purple flowers, in a sample of 160 pea plants.

A pea plant producing purple flowers had the genotype Aa.

This pea plant was crossed with a pea plant producing white flowers.

Complete the Punnett square to show the possible genotypes of the offspring.

Show the percentage of pea plants that produce white flowers in your answer.

Asexual reproduction can be used to produce flowering plants.

Give two advantages of using asexual reproduction to produce flowering plants.

Flower colour is controlled by genes.

Which is a definition of a gene?

The two strands of a DNA molecule are linked by complementary bases.

Describe how the complementary bases are linked in a DNA molecule.

Apple trees show genetic variation.

State one possible cause of genetic variation in apple trees.

The colour of an apple is an observable characteristic.

Which is the term for an observable characteristic?

Name the type of reproduction that produces genetically identical organisms.

Grafting is a technique used to grow some varieties of apple tree.

Figure 16 shows apple tree shoots grafted on to a rootstock.

Grafting can be used to produce apple trees that are genetically identical.

Give one advantage and one disadvantage of growing genetically identical apple trees.

advantage

disadvantage

As apples ripen, enzymes convert starch into sugars.

Devise a method to find the optimum pH of an enzyme that breaks down starch.

You may use standard laboratory equipment and the solutions listed in the box.

The optimum pH of an enzyme is pH 6.

Explain why this enzyme would not work at pH 10.

Name the type of reproduction that produces genetically identical organisms.

Grafting is a technique used to grow some varieties of apple tree.

Figure 3 shows apple tree shoots grafted on to a rootstock.

Grafting can be used to produce apple trees that are genetically identical.

Give one advantage and one disadvantage of growing genetically identical apple trees.

advantage

disadvantage

As apples ripen, enzymes convert starch into sugars.

Devise a method to find the optimum pH of an enzyme that breaks down starch.

You may use standard laboratory equipment and the solutions listed in the box.

The optimum pH of an enzyme is pH 6.

Explain why this enzyme would not work at pH 10.

Figure 9 shows a plant with plantlets growing from it.

If a plantlet touches soil, it will grow roots and become a new plant.

This is an example of asexual reproduction.

State one advantage of asexual reproduction for this plant.

Scientists investigated how temperature affected the number of plantlets produced by this type of plant in 10 weeks.

The scientists grew one of these plants in each of six temperatures.

Figure 10 shows the results.

Describe the effect of temperature on the number of plantlets produced by these plants.

Which of these would improve the results of this investigation?

The plant in Figure 9 also produces flowers for sexual reproduction.

Explain one advantage of sexual reproduction.

Figure 11 shows the characteristics of three different varieties of this plant.

A gardener wants to use selective breeding to produce a plant with large green and white striped leaves and large white flowers.

Explain which plants the gardener should use.

Gregor Mendel studied inheritance in pea plants.

Pea plants can produce either yellow pea pods or green pea pods.

Mendel crossed plants that always produce yellow pea pods with plants that always produce green pea pods.

Symbol A represents the dominant allele.

Symbol a represents the recessive allele.

Which is the genotype of the pea pods produced from this cross?

Mendel grew many plants from the seeds in these pea pods.

These plants were then crossed with each other.

The seeds from this second cross produced 5 496 plants with yellow pea pods and 1 832 plants with green pea pods.

Give this as a ratio in its simplest form.

Complete the Punnett square to show the outcome of a cross where both parent pea plants are heterozygous.

Show the percentage probability of homozygous recessive offspring in your answer.

percentage probability of homozygous recessive offspring_........

Some plants reproduce sexually.

Give one advantage of this type of reproduction.

Name the process that forms gametes for sexual reproduction.

7 Hipparion is an extinct genus of horse that lived between approximately 20 million and 0.8 million years ago. Figure 10 shows the skeletons of a Hipparion and a modern horse.

Hipparion modern horse (Sources: © Morphart Creation/Shutterstock and © Hein Nouwens/Shutterstock)

Figure 10

(a) (i) Give one method that can be used to date a fossil of a Hipparion.

(ii) Give one reason why scientists have concluded that the modern horse has evolved from Hipparion.

(b) Describe how racehorses alive today have been selectively bred to run faster.

* (c) Discuss the advantages and disadvantages of sexual reproduction and asexual reproduction.

Gregor Mendel used pea plants in plant breeding experiments. He discovered the basis of genetic inheritance.

He cross-bred tall pea plants with short pea plants.

All the offspring were tall, as shown in Figure 16.

Explain why the offspring are all tall.

In this investigation, the parent pea plants were grown in a warm, closed greenhouse.

Give two reasons why the parent pea plants were grown in a warm, closed greenhouse.

Pea plants produce different coloured peas.

The allele for yellow‑coloured peas (A) is dominant to the allele for green‑coloured peas (a).

Two heterozygous parent plants were used in a genetic cross.

Predict, using the Punnett square, the percentage probability that this cross will have offspring that produce green‑coloured peas.

Explain one advantage to pea plants of using sexual reproduction to produce offspring.

Peas contain small amounts of fat.

Describe a test to identify fat.

Gregor Mendel used pea plants in plant breeding experiments. He discovered the basis of genetic inheritance.

He cross-bred tall pea plants with short pea plants.

All the offspring were tall, as shown in Figure 4.

Explain why the offspring are all tall.

In this investigation, the parent pea plants were grown in a warm, closed greenhouse.

Give two reasons why the parent pea plants were grown in a warm, closed greenhouse.

Pea plants produce different coloured peas.

The allele for yellow‑coloured peas (A) is dominant to the allele for green‑coloured peas (a).

Two heterozygous parent plants were used in a genetic cross.

Predict, using the Punnett square, the percentage probability that this cross will have offspring that produce green‑coloured peas.

Explain one advantage to pea plants of using sexual reproduction to produce offspring.

Peas contain small amounts of fat.

Describe a test to identify fat.

Figure 1 shows a pea plant with flowers.

Name the type of reproduction involving flowers.

What is the advantage of reproduction involving flowers?

The 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).

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.

State the percentage of the offspring that will produce round seeds.

Which scientist discovered the basis of genetic inheritance by crossing pea plants?

The blood group of a person is determined by their genotype.

Describe how a person inherits the blood group AB.