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EnglandBiology

B5 Genes, inheritance and selection

6 dot points across 6 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How is genetic information stored in DNA, what is the genome, and what causes organisms to vary?

The structure of DNA as a double helix of nucleotides with complementary base pairing, the genome as the entire genetic material of an organism, the value of sequencing the human genome, and the causes of genetic and environmental variation including mutation.
A focused answer to the OCR Gateway GCSE Biology A topic B5 on DNA, the genome and variation, covering the double helix and complementary base pairing, genes and chromosomes, the genome and the value of the Human Genome Project, and the genetic and environmental causes of variation including mutation.
9 min answer →

How do alleles pass from parents to offspring, and how do we predict the ratios in a genetic cross?

Alleles, dominant and recessive, genotype and phenotype, homozygous and heterozygous, monohybrid crosses and Punnett squares, the inheritance of sex by the X and Y chromosomes, and single-gene inherited disorders such as cystic fibrosis and polydactyly.
A focused answer to the OCR Gateway GCSE Biology A topic B5 on genetic inheritance, covering alleles, dominant and recessive, genotype and phenotype, homozygous and heterozygous, monohybrid crosses with Punnett squares, the inheritance of sex, and single-gene inherited disorders such as cystic fibrosis and polydactyly.
10 min answer →

How does natural selection drive evolution, and what is the evidence that it happens?

Variation and natural selection, Darwin's theory of evolution by natural selection, the development of antibiotic-resistant bacteria, the evidence for evolution from fossils and from resistant bacteria, extinction, and the formation of new species by isolation.
A focused answer to the OCR Gateway GCSE Biology A topic B5 on natural selection and evolution, covering variation and selection, Darwin's theory of evolution by natural selection, antibiotic-resistant bacteria, the evidence from fossils, extinction, and the formation of new species by isolation.
10 min answer →

How does the base sequence of a gene get turned into a protein, and what happens when a mutation changes it?

Protein synthesis as transcription of a gene into mRNA and translation at the ribosome, the role of the triplet code and amino acids, how the order of bases determines the protein made, and how mutations can change a protein and its function.
A focused answer to the OCR Gateway GCSE Biology A topic B5 on protein synthesis, covering transcription of a gene into mRNA, translation at the ribosome, the triplet code and amino acids, how the base order determines the protein made, and how mutations can change a protein and its function.
9 min answer →

How do sexual and asexual reproduction differ, and how does meiosis make gametes that vary?

Sexual and asexual reproduction, the formation of gametes by meiosis, how meiosis halves the chromosome number and produces genetically varied cells, and the advantages and disadvantages of each type of reproduction.
A focused answer to the OCR Gateway GCSE Biology A topic B5 on reproduction and meiosis, covering sexual and asexual reproduction, how meiosis halves the chromosome number and produces genetically varied gametes, fertilisation, and the advantages and disadvantages of each type of reproduction.
9 min answer →

How do humans change the characteristics of organisms by selective breeding and by genetic engineering?

Selective breeding (artificial selection) and its uses and risks, the process and uses of genetic engineering including genetically modified crops and bacteria producing insulin, the benefits, risks and ethics of genetic modification, and an outline of tissue culture and cloning.
A focused answer to the OCR Gateway GCSE Biology A topic B5 on selective breeding and genetic engineering, covering artificial selection and its risks, the process and uses of genetic engineering including GM crops and bacteria producing insulin, the benefits, risks and ethics of genetic modification, and an outline of cloning.
9 min answer →