Genes, Inheritance and Selection | OCR GCSE Biology A, Foundation tier (J247)

Genes, Inheritance and Selection

144 questions
9 subtopics
Paper 2
Paper 2

Genes, Inheritance and Selection is examined in Biology A Paper 2.

It covers genetic terms, and the genome, genome, environment and mutations, asexual and sexual reproduction compared, haploid, diploid and meiosis, single gene inheritance and Punnett squares, sex determination, multiple genes and Mendel's work, variation within a population, and classification, natural selection and evolution and evidence for evolution, and the work of Darwin and Wallace.

Sample questions from Genes, Inheritance and Selection

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

Genetic terms, and the genome

What does homozygous mean?

Show the answer
Carrying two identical alleles of a gene.
Genome, environment and mutations

Explain why height in humans shows continuous variation.

Show the answer
It is controlled by several genes acting together, and it is also affected by environmental factors such as diet.
Asexual and sexual reproduction compared

Give two disadvantages of sexual reproduction.

Show the answer
Two parents must find each other and mate, and reproduction is slower with fewer offspring produced.
Haploid, diploid and meiosis

A plant has 14 chromosomes in each of its leaf cells. How many chromosomes are in each of its pollen grain nuclei?

Show the answer
Seven, because gametes are haploid and carry half the number found in a body cell.
Single gene inheritance and Punnett squares

Two black-furred animals produce a brown-furred offspring, where the allele B for black is dominant to the allele b for brown. Explain how this is possible.

Show the answer
Both parents are heterozygous Bb, so each can pass on b and produce a bb offspring.
Sex determination, multiple genes and Mendel's work

Are most phenotypic features controlled by one gene or by many genes?

Show the answer
By many genes acting together.
Variation within a population, and classification

What does it mean to say there is extensive genetic variation within a population of a species?

Show the answer
The individuals in it differ from one another in the alleles they carry, so no two are genetically identical apart from clones.
Natural selection and evolution

Does an individual organism evolve during its own lifetime?

Show the answer
No, individuals do not evolve; it is the population that changes across generations.

The 9 subtopics

One subtopic is one session. Work down the list.

Subtopic	What it covers	Questions
Genetic terms, and the genome	What gametes, chromosomes, genes and alleles are, dominant and recessive alleles, homozygous and heterozygous, genotype and phenotype, writing genotypes and working out a phenotype, what a genome is and that it includes non-coding DNA, how a gene and a genome differ, where the genome is found, why individuals' genomes differ, and what sequencing a genome means.	18
Genome, environment and mutations	How the genome and the environment together determine phenotype, discontinuous and continuous variation with examples such as eye colour and height and how each is usually controlled, mutations as the source of all genetic variants, the three possible effects of a mutation on the phenotype and which is rarest, why most have no effect, and why not all mutations are harmful.	16
Asexual and sexual reproduction compared	The advantages and disadvantages of asexual and sexual reproduction, why an asexual population can be wiped out by a new disease, how offspring numbers compare between bacteria and large mammals, when asexual reproduction is an advantage, why many plants reproduce both ways, and why the variation from sexual reproduction helps a population survive a new predator.	9
Haploid, diploid and meiosis	What haploid and diploid mean, human chromosome numbers in body cells and gametes, why a fertilised egg and an embryo's cells are diploid, how meiosis halves the chromosome number to make four gametes, how meiosis and fertilisation keep the number constant, meiosis as a source of variation, where it happens, and how it compares with mitosis.	15
Single gene inheritance and Punnett squares	What single gene inheritance is, predicting offspring genotypes and phenotypes from crosses of homozygous and heterozygous parents, what a carrier is and why a recessive characteristic needs two recessive alleles, a test cross to find an unknown genotype, using Punnett squares to give ratios, numbers and probabilities, and why each fertilisation is independent.	16
Sex determination, multiple genes and Mendel's work	The X and Y chromosomes and which parent decides a child's sex, the Punnett square for the cross, characteristics controlled by many genes, and Mendel's pea crosses and their late acceptance.	21
Variation within a population, and classification	How much genetic variation a population holds and where it comes from, why individuals carry the same genes in different variants, why variation helps a population and sexual reproduction gives more of it, what classification is, artificial and natural classification with examples, molecular phylogenetics and how DNA sequencing reveals relationships, and why classification changes over time.	16
Natural selection and evolution	What natural selection is, where variation comes from, the steps from mutation to a changed population, why individuals do not evolve, what evolution and a species are, and how new species form.	16
Evidence for evolution, and the work of Darwin and Wallace	Fossils and antibiotic resistance as evidence for evolution, why the fossil record is incomplete, how bacteria become resistant, Darwin's and Wallace's theory and its slow acceptance, and what seedbanks preserve.	17

Genes, Inheritance and Selection is 144 of the 981 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.