AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Sexual and asexual reproduction: In sexual reproduction there is mixing of genetic information which leads to variety in the offspring. The formation of gametes involves meiosis.
Sexual reproduction combines genetic material from two parents, so each offspring receives a mixture of alleles and is genetically different from its parents and siblings.
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Sexual reproduction combines genetic material from two parents, so each offspring receives a mixture of alleles and is genetically different from its parents and siblings. Gametes are formed by meiosis, a type of cell division that halves the chromosome number. In meiosis, copies of the genetic information are made, and then the cell divides twice to form four gametes, each with a single set of chromosomes. All four gametes are genetically different from each other. For example, human sperm and egg cells each contain 23 chromosomes. When they fuse during fertilisation, the full number of 46 is restored. This mixing of genetic information leads to variety in the offspring.
What earns the marks
- Sexual reproduction involves the fusion of male and female gametes, mixing genetic information from two parents.
- Meiosis halves the chromosome number, producing gametes with a single set of chromosomes.
- In meiosis, copies of the genetic information are made before the cell divides twice.
- Meiosis produces four gametes that are all genetically different from each other.
- Random fertilisation of gametes restores the full number of chromosomes and adds further genetic variation.
- The resulting offspring show variety and are genetically different from each other and from their parents.
Common mistakes and how to put them right
Saying meiosis produces two identical cells.
Put it right by stating it produces four genetically different cells.
Confusing meiosis with mitosis.
Put it right by noting mitosis produces two genetically identical cells for growth and repair.
Stating that gametes have the full number of chromosomes.
Put it right by stating gametes have half the number so that fertilisation restores the full set.
Exam tips
- Compare meiosis and mitosis in a table: number of divisions, number of cells produced, and genetic variation.
- State clearly that meiosis halves the chromosome number, and fertilisation restores it.
- Explain variety by referring to the mixing of genetic information from two parents and the formation of non-identical gametes.
Try the lesson
The start of the Sexual and asexual reproduction: In sexual reproduction there is mixing of genetic information which leads to variety in the offspring. The formation of gametes involves meiosis. lesson, made from checked teaching notes for this specification point.
Have a go first
Which type of cell division produces gametes?
Listen
Sexual reproduction combines genetic material from two parents, so each offspring receives a mixture of alleles and is genetically different from its parents and siblings. Gametes are formed by meiosis, a type of cell division that halves the chromosome number. In meiosis, copies of the genetic information are made, and then the cell divides twice to form four gametes, each with a single set of chromosomes. All four gametes are genetically different from each other. For example, human sperm and egg cells each contain 23 chromosomes. When they fuse during fertilisation, the full number of 46 is restored. This mixing of genetic information leads to variety in the offspring. A strong answer earns marks for these points. Sexual reproduction involves the fusion of male and female gametes, mixing genetic information from two parents. Meiosis halves the chromosome number, producing gametes with a single set of chromosomes. In meiosis, copies of the genetic information are made before the cell divides twice. Meiosis produces four gametes that are all genetically different from each other. A common slip: Saying meiosis produces two identical cells. Instead, stating it produces four genetically different cells. Exam tip: Compare meiosis and mitosis in a table: number of divisions, number of cells produced, and genetic variation.
See it
Put it in order
Put these steps in the order they happen.
- 1. Cell divides twice
- 2. Four gametes formed
- 3. Each gamete has a single set of chromosomes
- 4. All four gametes genetically different from each other
- 5. Male and female gametes fuse
- 6. Full number of chromosomes restored
- 7. Variety in the offspring
- 8. Copies of genetic information made
Key words
Say what each word means before you turn the card.
Genetic variation
Try answering aloud or in your head before turning the card.
Meiosis and gamete formation
Try answering aloud or in your head before turning the card.
Sexual reproduction and inheritance
Try answering aloud or in your head before turning the card.
See every definition
- Genetic variation
- Mixing of genetic information in sexual reproduction leads to variety in the offspring.
- Meiosis and gamete formation
- The formation of gametes involves meiosis, in which copies of the genetic information are made and then the cell divides twice to form four gametes.
- Sexual reproduction and inheritance
- In sexual reproduction there is mixing of genetic information which leads to variety in the offspring.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
There is more to this lesson
The full lesson goes on to check your understanding and help you earn the marks. Create a free account to carry on, with your progress saved.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge
Test your understanding of Sexual and asexual reproduction: In sexual reproduction there is mixing of genetic information which leads to variety in the offspring. The formation of gametes involves meiosis.
Active recall beats re-reading. Take an instant quiz now to test what you’ve learned and lock it into long-term memory.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge