Genetics | Edexcel GCSE Combined Science Biology, Foundation tier (1SC0)
Genetics
- 111 questions
- 9 subtopics
- Paper 1
- Paper 1
Genetics is examined in Paper 1, Biology 1.
It covers meiosis, DNA structure, genes and the genome, extracting DNA from fruit, alleles, genotype and phenotype, monohybrid crosses, sex determination and probability, genetic and environmental variation, the Human Genome Project and mutation.
Sample questions from Genetics
Answer each one closed book first, then open the answer.
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Meiosis and the formation of gametes
How does the chromosome number of a cell made by meiosis compare with that of the parent cell?
Show the answer
Each daughter cell has half the number of chromosomes of the parent cell. -
DNA structure, genes and the genome
What type of bond holds a pair of bases together across the two strands?
Show the answer
Weak hydrogen bonds hold each base pair together. -
Extracting DNA from fruit
Why is salt added to the mixture when extracting DNA from fruit?
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The salt makes the DNA molecules stick together so they can be seen. -
Alleles, genotype and phenotype
What is a chromosome?
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A chromosome is a long, coiled molecule of DNA found in the nucleus that carries many genes. -
Monohybrid crosses and sex determination
A homozygous dominant parent is crossed with a homozygous recessive parent. Describe the genotypes and phenotypes of the offspring.
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All the offspring are heterozygous and all show the dominant characteristic. -
Probability and ratios from genetic crosses
Two heterozygous parents are crossed. What percentage of their children are expected to be heterozygous?
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50% of the children are expected to be heterozygous. -
Causes of variation: genes and environment
Name the two sources of genetic variation.
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Mutation and sexual reproduction. -
The Human Genome Project
Describe how the Human Genome Project can help predict a person's risk of disease.
Show the answer
Alleles linked to particular diseases can be identified, so people carrying them can be monitored or advised early.
The 9 subtopics
One subtopic is one session. Work down the list.
| Subtopic | What it covers | Questions |
|---|---|---|
| Meiosis and the formation of gametes | Where meiosis takes place, the four haploid daughter cells it makes with half the chromosome number, the 23 chromosomes in a human gamete, why gametes must be haploid for fertilisation, and how the random sharing of chromosomes makes gametes and children genetically different. | 8 |
| DNA structure, genes and the genome | DNA as a double helix polymer of nucleotides made of a sugar, a phosphate and one of four bases, complementary base pairing held by weak hydrogen bonds, genes as sections of DNA coding for proteins, the genome, and why people with the same genes can differ. | 15 |
| Extracting DNA from fruit | Extracting DNA from fruit by mashing, adding detergent and salt, filtering and pouring on ice-cold ethanol, why the DNA comes out of solution as a white stringy layer, and why the mixture is stirred gently. | 8 |
| Alleles, genotype and phenotype | Alleles and why individuals of a species differ, dominant and recessive alleles and how a recessive allele can be carried unseen, chromosomes and genes, homozygous and heterozygous, genotype and phenotype, gametes and zygotes, and why one phenotype can hide different genotypes. | 18 |
| Monohybrid crosses and sex determination | Monohybrid inheritance and Punnett squares, the ratios from heterozygous and homozygous crosses, reading a family pedigree, and how the X and Y chromosomes decide sex. | 15 |
| Probability and ratios from genetic crosses | The probabilities and percentages expected from heterozygous and homozygous recessive crosses, turning offspring counts into whole-number ratios, and why real results rarely match the prediction. | 8 |
| Causes of variation: genes and environment | Characteristics controlled by many genes such as height and their continuous range, genetic variation from mutation and sexual reproduction, acquired characteristics and environmental variation, identical twins, and presenting variation with frequency tables, histograms, bar charts and the modal class. | 19 |
| The Human Genome Project | The aim and outcomes of the Human Genome Project, testing for inherited disorders and predicting disease risk, personalised medicine and new drug treatments, tracing human migration, and concerns about insurers, employers and knowing the risk of an untreatable disease. | 9 |
| Genetic variation and the effects of mutation | Extensive genetic variation within a population, mutations as random changes in base sequence and the source of new variation, why most mutations have no effect on the phenotype, the rare ones that stop a protein working, and mutations that give an advantage. | 11 |
How the guide is worked
Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.
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Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
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Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.
Read the full method, the return schedule and the research behind it.
Nearby topics
Edexcel GCSE Combined Science Biology, Foundation tier Active Recall Guide
Every topic, not just this one. 904 questions with their answers.