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Reproduction
Study how genetic information is copied, halved, inherited and expressed in AQA GCSE Biology 8461, including meiosis, DNA, Punnett squares and inherited disorders.
72
Objectives
10
Flashcards
10
Questions
90 min
Study time
AqaGcseBiologyInheritance, variation and evolution
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Syllabus checklist
What you need to know
72 objective pages available
Sexual and asexual reproduction6 objectives
- Describe sexual reproduction as the joining or fusion of male and female gametes.
- Identify sperm and egg cells as animal gametes and pollen and egg cells as flowering plant gametes.
- Explain that sexual reproduction mixes genetic information and produces variation in offspring.
- State that gamete formation in sexual reproduction involves meiosis.
- Describe asexual reproduction as reproduction involving one parent, no gamete fusion and no mixing of genetic information.
- Explain that asexual reproduction produces genetically identical offspring called clones and involves only mitosis.
Meiosis8 objectives
- Explain how meiosis halves the number of chromosomes in gametes.
- Explain how fertilisation restores the full number of chromosomes.
- State that cells in reproductive organs divide by meiosis to form gametes.
- Describe that before meiosis copies of the genetic information are made.
- Describe that meiosis involves two cell divisions to form four gametes, each with a single set of chromosomes.
- Explain that gametes are genetically different from each other and that knowledge of detailed meiosis stages is not required.
- Explain that after fertilisation the new cell divides by mitosis and embryo cells differentiate during development.
- Use models to represent chromosome behaviour during meiosis.
Advantages and disadvantages of sexual and asexual reproduction (biology only)10 objectives
- Explain that sexual reproduction produces variation in offspring.
- Explain that variation can give a survival advantage if the environment changes.
- Explain that humans can speed up natural selection through selective breeding to increase food production.
- Describe advantages of asexual reproduction, including one parent, faster reproduction, lower time and energy cost, and many identical offspring in favourable conditions.
- Explain why organisms may reproduce by sexual or asexual methods depending on circumstances.
- Describe how malarial parasites reproduce asexually in the human host and sexually in the mosquito.
- Describe how many fungi reproduce asexually by spores and sexually to produce variation.
- Describe plant asexual reproduction using runners in strawberry plants and bulb division in daffodils.
- Explain advantages and disadvantages of sexual and asexual reproduction for an unfamiliar organism when given information.
- State that knowledge of reproduction examples is restricted to the organisms named in the specification.
DNA and the genome7 objectives
- Describe DNA as the genetic material in the nucleus of a cell.
- Describe DNA as a polymer made of two strands forming a double helix.
- Explain that DNA is contained in structures called chromosomes.
- Define a gene as a small section of DNA on a chromosome.
- Explain that each gene codes for a sequence of amino acids to make a specific protein.
- Define the genome as the entire genetic material of an organism.
- Discuss the importance of understanding the human genome for finding disease-linked genes, understanding inherited disorders and tracing human migration patterns.
DNA structure (biology only)15 objectives
- Describe DNA as a polymer made from repeating nucleotide units.
- Describe each nucleotide as containing a sugar, phosphate group and one of four bases.
- Recall that DNA contains the four bases A, C, G and T.
- Explain that a sequence of three bases codes for a particular amino acid.
- Explain that the order of bases controls the order of amino acids in a protein.
- Describe the long DNA strands as alternating sugar and phosphate sections with bases attached to the sugars.
- Interpret diagrams of DNA structure without needing to reproduce them.
- Recall (HT only) a simple description of protein synthesis on ribosomes using a template and carrier molecules.
- Explain (HT only) how DNA structure affects the protein made by controlling the amino acid sequence.
- Describe (HT only) how complementary bases pair, with C linked to G and T linked to A.
- Explain (HT only) how a mutation may change the protein synthesised by a gene.
- Describe (HT only) how genetic variants in coding DNA can alter protein activity and influence phenotype.
- Describe (HT only) how variants in non-coding DNA can alter gene expression and influence phenotype.
- State (HT only) that detailed mRNA, tRNA, amino acid and protein structure is not required.
- Model insertions and deletions in chromosomes to illustrate mutations.
Genetic inheritance14 objectives
- Explain the terms gamete, chromosome and gene.
- Explain the terms allele, dominant and recessive.
- Explain the terms homozygous and heterozygous.
- Explain the terms genotype and phenotype.
- Use examples such as fur colour in mice and red-green colour blindness in humans to explain single-gene characteristics.
- Explain that different forms of a gene are called alleles.
- Explain how genotype operates at a molecular level to produce a phenotype.
- Explain that a dominant allele is expressed if one copy is present.
- Explain that a recessive allele is expressed only when two copies are present and no dominant allele is present.
- Explain that most characteristics result from multiple genes interacting rather than single-gene inheritance.
- Use probability to predict the results of a single-gene cross.
- Use direct proportion and simple ratios to express outcomes of a genetic cross.
- Complete Punnett square diagrams and extract information from genetic crosses and family trees.
- Construct (HT only) a genetic cross using a Punnett square and use probability to make predictions.
Inherited disorders6 objectives
- Explain that inherited disorders are caused by the inheritance of particular alleles.
- Describe polydactyly as an inherited disorder caused by a dominant allele.
- Describe cystic fibrosis as an inherited disorder of cell membranes caused by a recessive allele.
- Use inheritance patterns to explain why dominant and recessive disorders appear in offspring.
- Make informed judgements about economic, social and ethical issues linked to embryo screening when given information.
- Consider that embryo screening and gene therapy may alleviate suffering but raise ethical issues.
Sex determination6 objectives
- Recall that ordinary human body cells contain 23 pairs of chromosomes.
- State that 22 chromosome pairs control characteristics only and one pair determines sex.
- Describe females as having XX sex chromosomes.
- Describe males as having XY sex chromosomes.
- Carry out a genetic cross to show sex inheritance.
- Use direct proportion and simple ratios in sex-determination genetic crosses.
Key terms
GameteFusiongametessperm and egg cellssexual reproductionvariationGamete formationMeiosisasexual reproductiongamete fusionclonesGametes
Exam tips
- Understand Gamete Fusion: Clearly describe the process of gamete fusion in sexual reproduction, emphasizing the roles of male and female gametes.
- Know Your Gametes: Memorize the types of gametes: identify sperm and egg cells in animals, and pollen and egg cells in flowering plants.
Common mistakes
- Confusing fusion with fertilisation: Explain that fusion is the physical merging of the sperm and egg membranes, while fertilisation is the complete combination of their nuclei and chromosomes, which restores the full diploid set and initiates the zygote’s development.
- Misidentifying Gametes: Remember that sperm and egg cells are specifically animal gametes, while pollen and egg cells are the gametes found in flowering plants.
Practice preview
- Which option best matches the approved learning objective for Sexual and asexual reproduction (1)?
- Which option correctly contrasts the named ideas for Reproduction, Sexual and asexual reproduction: students must describe sexual reproduction as the joining or fusion of male and female gametes.
- Which option gives the correct cause-and-effect relationship for Reproduction, Sexual and asexual reproduction: students must describe sexual reproduction as the joining or fusion of male and female gametes.
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