Sexual and asexual reproduction, how meiosis halves the chromosome number, how DNA, genes and the genome fit together, and transcription and translation (Edexcel Higher, Biology only).
What you will learn
- Compare sexual and asexual reproduction
- Work out chromosome numbers in gametes and body cells
- Use 2ⁿ to count the possible gametes
- Describe DNA, chromosomes, genes and the genome
- Describe transcription and translation and pair codons with anticodons (Edexcel and OCR Higher, Biology only)
Two ways to reproduce
Sexual reproduction joins two gametes (sex cells): sperm and egg in animals, pollen and egg cells in flowering plants.
Each offspring gets a mix of genetic information from two parents, so the offspring vary.
Asexual reproduction needs one parent and no gametes. The new cells are made by mitosis, so the offspring are genetically identical clones. Strawberry runners, bacteria splitting in two and potato tubers are all asexual.
Biology only: sexual reproduction is slower but gives variation, so some offspring may survive if the environment changes. Asexual reproduction is faster and needs no mate.
The rest of this lesson and its 13 practice questions are locked.
In this lesson
- Two ways to reproduce
- Meiosis halves the number
- DNA, genes and the genome
- Transcription and translation (Edexcel and OCR Higher, Biology only)
- Try it: Halve it, then double it
13 practice questions, marked as you go; about 20 minutes in all.
Key terms
Sexual reproduction, Gametes, Vary, Asexual reproduction, Mitosis, Clones, Meiosis, Twice, Four, Fertilisation
In this unit: Inheritance, variation and evolution
Meiosis and DNA, Punnett squares and family trees, inherited disorders and embryo screening, natural selection, selective breeding, genetic engineering and cloning, and classification.