Biology · OCR Paper 2
Inheritance
How genetic information is passed from one generation to the next, from the genome, genes, alleles and variants to the causes of variation, mutations and their effects, the advantages and disadvantages of asexual and sexual reproduction, the role of meiosis in making haploid gametes, single gene crosses and sex determination, and the work of Mendel. Matches OCR GCSE Biology A (Gateway Science) B5.1a to B5.1m. Genes, the genome and phenotype, variation and mutations, meiosis, and single gene inheritance are for both Combined Science and separate Biology. Asexual and sexual reproduction (B5.1f) and Mendel (B5.1m) are for separate Biology only. Genetic variants and phenotype (B5.1e) is for separate Biology and the Higher tier only.
Lessons
Ticks are remembered on this device only.
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1
Genes, the Genome and Phenotype
Every cell in your body contains the instructions for making you, but what you look like depends on more than those instructions. This lesson covers the key…
9 terms -
2
Variation and Mutations
No two people are exactly alike, and neither are two peas in a pod. This lesson covers continuous and discontinuous variation, the causes of variation, and how…
9 terms -
3
Genetic Variants and Phenotype (Higher tier)
A change in one base can have no effect, or it can switch a gene off or change an enzyme. This lesson is for separate Biology only, and for the Higher tier…
9 terms -
4
Asexual and Sexual Reproduction
Some organisms reproduce on their own, and others need a partner. This lesson is for separate Biology only: Combined Science students do not need it. It…
9 terms -
5
Meiosis, Haploid and Diploid
Your body cells have 46 chromosomes, but your gametes have only 23. This lesson explains the terms haploid and diploid, and the role of meiotic cell division…
9 terms -
6
Single Gene Inheritance and Punnett Squares
If you know the genotypes of two parents, you can predict what their offspring will be like. This lesson covers single gene inheritance, how to use Punnett…
9 terms -
7
Mendel and the Development of Genetics
Genetics began in a monastery garden, with a monk who counted peas. This lesson is for separate Biology only: Combined Science students do not need it. It…
9 terms
Key terms in this chapter
All 63, gathered from every lesson.
- Gene
- A section of DNA that codes for a protein.
- Allele
- A different version of a gene, also called a variant.
- Genome
- The entire genetic material of an organism.
- Genotype
- The alleles that an organism has for a gene.
- Phenotype
- The observable features of an organism, caused by the genotype and the environment.
- Dominant
- Describes an allele that shows its effect even when only one copy is present.
- Recessive
- Describes an allele whose effect only shows when there are two copies.
- Homozygous
- Having two identical alleles of a gene.
- Heterozygous
- Having two different alleles of a gene.
- Variation
- The differences between individuals of the same species.
- Discontinuous variation
- Variation in which individuals fall into distinct categories.
- Continuous variation
- Variation in which a feature can have any value within a range.
- Mutation
- A random change in the base sequence of DNA.
- Variant
- A different version of a gene, which arose from a mutation.
- Mutagen
- Something that increases the rate of mutation, such as ionising radiation.
- Histogram
- A bar chart for continuous data, in which the bars touch.
- Mode
- The value that occurs most often.
- Environment
- The surroundings and conditions in which an organism lives.
- Coding DNA
- The parts of the DNA that code for proteins, which are the genes.
- Non-coding DNA
- Parts of the DNA that do not code for proteins, but may control how genes are used.
- Gene expression
- The way in which a gene is used to make its protein.
- Transcription
- The copying of the DNA of a gene into mRNA.
- Active site
- The part of an enzyme where the substrate binds.
- Enzyme-substrate complex
- The enzyme and its substrate joined together.
- Frameshift
- A change in all of the triplets after an addition or deletion of bases.
- Variant
- A different version of a gene, which arose from a mutation.
- Protein structure
- The shape of a protein, which depends on the order of its amino acids.
- Asexual reproduction
- Reproduction involving one parent, with no gametes, producing genetically identical offspring.
- Sexual reproduction
- Reproduction involving the fusion of gametes from two parents, producing genetically different offspring.
- Clone
- A genetically identical copy of an organism.
- Environmental pressure
- A factor such as disease, predators or a change in climate, which affects survival.
- Offspring
- The young produced by a parent organism.
- Runner
- A stem that grows along the ground and makes new plants, as in strawberries.
- Mitosis
- Cell division that gives two genetically identical cells.
- Meiosis
- Cell division that gives four genetically different gametes.
- Colonise
- To spread into and settle in a new habitat.
- Meiosis
- A type of cell division that produces four genetically different haploid gametes.
- Haploid
- Having one set of chromosomes, as in a gamete.
- Diploid
- Having two sets of chromosomes, as in a body cell.
- Gamete
- A sex cell, such as a sperm cell or an egg cell.
- Fertilisation
- The fusion of a male gamete and a female gamete.
- Zygote
- The cell formed when two gametes fuse. It is diploid.
- Embryo
- An early stage of development of an organism, formed from the zygote.
- Chromosome
- A long molecule of DNA that carries genes.
- Genetic variation
- Differences in the genes of individuals of the same species.
- Single gene cross
- A cross that looks at the inheritance of one gene.
- Punnett square
- A grid that shows the possible combinations of gametes in a cross.
- Genotype
- The alleles that an organism has for a gene.
- Phenotype
- The feature that an organism shows.
- Carrier
- A person who has a recessive allele but does not show the disorder.
- Probability
- The chance that an event will happen.
- Sex chromosomes
- The pair of chromosomes that decides the sex of a person: XX in a female and XY in a male.
- Ratio
- A comparison of numbers, such as 3 : 1.
- Test cross
- A cross with a homozygous recessive individual to find an unknown genotype.
- Blending inheritance
- The idea that the features of parents mix in their offspring.
- Pure-breeding
- Producing offspring that are always the same as the parent.
- Cross-pollination
- The transfer of pollen from one plant to the flower of another plant.
- P generation
- The parental generation in a cross.
- F1 generation
- The first generation of offspring from a cross.
- F2 generation
- The offspring from the cross of F1 individuals.
- Inherited factor
- Mendel's name for what we now call a gene.
- Chromosome
- A long molecule of DNA that carries genes.
- Genome
- The entire genetic material of an organism.