A genetic variant in a gene creates an allele (a different version of the gene), which produces a different phenotype.

One or both dominant alleles in the genotype for the characteristic to be expressed in the phenotype.

Two recessive alleles in the genotype for the characteristic to be expressed in the phenotype.

The combination of alleles an organism has for a characteristic (i.e. phenotype).

Features that result, at least partly, from the genetic code of an organism’s genes.

Alleles, genotype, and phenotype

Combined science

Models of single-gene inheritance: Punnett squares

Models of single-gene inheritance: family tree diagrams

The inheritance of biological sex in humans

Pupils will learn about growth through cell division, mitosis as part of the cell cycle, cancer as the result of changes in cells that lead to uncontrolled growth and division, and the formation of gametes by meiosis.

Pupils learned about what the genome is, what it’s made of and where it’s stored, more detail about the chemical structure of DNA, and the relationship between an organism’s genome and its phenotype.

This unit covers key genetic terms, single-gene inheritance, and genetic crosses, including probability and ratios. It explores how most traits result from multiple genes and sex determination in humans. The unit also includes interpreting data and using models to solve problems.

Inheritance, genotype and phenotype

A model used to show the inheritance of alleles from parents to offspring.

A sex cell (i.e. sperm and egg) that carries half the genetic information required for an individual organism.

The combination of alleles that an individual has for each gene.

Shows hows how much of one value there is compared to another.

A measure of the chance or likelihood of an event occurring.

A family tree diagram is a model of inheritance, showing whether a characteristic was passed from parents to offspring.

The genotype is the combination of alleles that an individual has for each gene.

The phenotype is the physical characteristics of an organism.

A carrier of a recessive genetic disorder does not express the disorder in their phenotype, but has one recessive allele in their genotype that can be passed to offspring.

Inheritance is the passing of genetic information from parents to offspring by reproduction.

The process of producing offspring where a male and a female provide half the genetic material via gametes.

Male or female as determined by the combination of sex chromosomes inherited (i.e. XX female, XY male).

The chromosomes that determine the reproductive and secondary sexual characteristics (i.e. X and Y).

Chemical messengers, secreted by glands, that help to control the reproductive and secondary sexual characteristics.

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Inheritance, genotype and phenotype

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