Genetics | Edexcel GCSE Biology, Higher tier (1BI0)

Genetics

179 questions
14 subtopics
Paper 1
Paper 1

Genetics is examined in Paper 1, Biology 1.

It covers asexual and sexual reproduction, meiosis, DNA structure, genes and the genome, extracting DNA from fruit, protein synthesis and the effects of genetic variants, Mendel's work and the inheritance of blood groups, alleles, genotype and phenotype, monohybrid crosses, sex determination and probability, sex-linked disorders, genetic and environmental variation, the Human Genome Project and mutation.

Sample questions from Genetics

Answer each one closed book first, then open the answer.

Asexual and sexual reproduction

Explain why a new disease can wipe out an entire population of asexually produced organisms.

Show the answer
Every individual is genetically identical, so if one is susceptible to the pathogen they all are.
Meiosis and the formation of gametes

Why are the gametes produced by meiosis genetically different from one another?

Show the answer
The chromosomes are shared out at random, so each gamete receives a different combination of alleles.
Extracting DNA from fruit

Why is salt added to the mixture when extracting DNA from fruit?

Show the answer
The salt makes the DNA molecules stick together so they can be seen.
Protein synthesis: transcription and translation

What is a codon?

Show the answer
A codon is a triplet of three bases in mRNA that codes for one specific amino acid.
Mendel's work and the inheritance of blood groups

Explain why inheritance was so difficult to understand before Mendel's time.

Show the answer
Nobody knew that chromosomes, genes or DNA existed, so there was no known mechanism for passing characteristics on.
Alleles, genotype and phenotype

What does heterozygous mean?

Show the answer
Heterozygous means having two different alleles of a particular gene.
Probability and ratios from genetic crosses

Two heterozygous parents are crossed. What percentage of their children are expected to be heterozygous?

Show the answer
50% of the children are expected to be heterozygous.
Sex-linked disorders

A carrier mother and an unaffected father have children. What percentage of their sons are expected to be affected?

Show the answer
50% of their sons are expected to be affected.

The 14 subtopics

One subtopic is one session. Work down the list.

Subtopic	What it covers	Questions
Asexual and sexual reproduction	Asexual reproduction producing clones, its advantages of needing no mate and reproducing rapidly and the risk its lack of variation brings, and how fertilisation in sexual reproduction produces variation that helps a population survive disease and changing conditions.	15
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
Protein synthesis: transcription and translation	How the base order sets the amino acid order and the protein's shape, then transcription by RNA polymerase, mRNA, codons, tRNA and the ribosome joining a polypeptide.	17
Genetic variants in coding and non-coding DNA	Where the non-coding DNA lies, how a variant there changes how much protein is made, and how a variant in coding DNA alters the amino acid sequence and the protein's activity.	12
Mendel's work and the inheritance of blood groups	Mendel's pea plant crosses, the 3:1 ratio, why his ideas were slow to be accepted, and the three ABO alleles, codominance and the blood groups they give.	16
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
Sex-linked disorders	Sex-linked disorders carried on the X chromosome such as red-green colour blindness, why males are affected more often, female carriers, why fathers cannot pass the allele to their sons, the chances from a carrier mother's cross, and how a daughter can be affected.	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

Genetics is 179 of the 1,386 questions in the guide.Get the guide, £7

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.

Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
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.
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.