20 terms

IGCSE Biology - Variation and Inheritance

Key terms from Edexcel IGCSE Biology on the topic of Variation and Inheritance
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Chromosome
Supercolied thread of DNA.
Gene
Short section of DNA that codes for a protein.
Three examples of human proteins
Haemoglobin, Amylase, and Lipase.
Allele
An alternative form of a gene
Homozygous
Two identical alleles of a gene (TT,tt).
Heterozygous
Two different alleles of a gene (Tt, tT).
Dominant allele
always expressed in the phenotype (whenever present) e.g. Ff or FF
Recessive allele
only expressed in the phenotype if the dominant allele is absent e.g. ff
Genotype
the alleles present in the nuclei of an organism.
Phenotype
the physical or chemical expression of the genotype
Double Helix
The shape of DNA.
Gamete
Sex cells e.g. sperm or egg.
Zygote
A fertilised egg cell.
Nucleus
Where the DNA is located in a cell.
A person with this genotype would have cystic fibrosis
ff
A person with either of these genotypes would not have CF
Ff or FF
A person with this genotype would be described as a carrier for cystic fibrosis
Ff
Heterozygous
the alleles of a particular gene are different e.g. Ff.
A person with either of these genotypes would have polydactyly
Dd or DD
A person with this genotype would not have polydactyly
dd
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