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Genes, chromosomes and alleles
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Genes are instructions stored in DNA. Different versions of a gene explain inherited differences.
Genome and genes
The genome is the entire DNA of an organism.
A gene is a section of a molecule of DNA that codes for a specific protein.
The nucleus contains chromosomes, and genes are found on the chromosomes.
A gene is a section of a molecule of DNA that codes for a specific protein.
The nucleus contains chromosomes, and genes are found on the chromosomes.
Alleles
Genes exist in different forms called alleles.
Different alleles of the same gene give differences in inherited characteristics, for example different eye colours.
Chromosomes come in pairs, so a body cell has two alleles of each gene: one from each parent.
Different alleles of the same gene give differences in inherited characteristics, for example different eye colours.
Chromosomes come in pairs, so a body cell has two alleles of each gene: one from each parent.
Polygenic inheritance
A few features are controlled by a single gene.
But most phenotypic features are the result of polygenic inheritance: several genes acting together.
Examples: height and skin colour. These show a smooth range of values (continuous variation).
But most phenotypic features are the result of polygenic inheritance: several genes acting together.
Examples: height and skin colour. These show a smooth range of values (continuous variation).
Height is controlled by many genes. What is this called, and what kind of variation does it give?
- Many genes affecting one feature is polygenic inheritance.
- It gives a smooth range of heights.
Answer: Polygenic inheritance; continuous variation
The genome is all an organism's DNA. A gene is a section of DNA coding for a protein. Genes are on chromosomes in the nucleus. Alleles are different forms of a gene. Most features are polygenic, controlled by several genes.
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