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16 Cards in this Set
- Front
- Back
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Gene |
A sequence of bases on a DNA molecule that codes for a protein, which results in a characteristic, e.g. a generator for eye colour |
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Allele |
A different version of a gene. There can be many different alleles of a single gene, but most plants and animals, including humans o ly carry two alleles of each gene, one from each parent. The order of bases in each allele is slightly different - they code for different versions of the same characteristic. |
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Genotype |
The genetic constitution of an organism - the alleles an organism has, e.g. BB, Bb or bb for eye colour |
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Phenotype |
The expression of the genetic constitution and it's interaction with the environment - an organisms characteristics, e.g. Brown eyes. |
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Dominant |
An allele whose characteristic appears in the phenotype even when there's only one copy. Dominant alleles are shown by a capital letter. |
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Recessive |
An allele whose characteristic only appears in the phenotype if two copies are present. Recessive alleles are shown by a lower case letter. |
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Codominant |
Alleles that are both expressed in the phenotype - neither one is recessive. |
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Locus |
The fixed position of a gene on a chromosome. Alleles of a gene are found at the same locus on peach chromosome in each pair. |
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Homozygote |
An organism that carries two copies of the same allele, e.g. BB or bb |
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Heterozygote |
An organism that carries two different alleles, e.g. Bb. |
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Carrier |
A person carrying an allele which is not expressed in the phenotype but can be passed on to offspring |
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Genetic diagrams |
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Phenotypic ratios |
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What are sex-linked characteristics? |
A characteristic is said to be sex-linked when the allele that codes for it is located on a sex chromosome. Males are more likely to show recessive phenotypes for genes that are sex-linked because they only have one X chromosome. |
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What is autosomal linkage? |
Genes on the same autosome (any chromosome that isn't a sex chromosome) can be 'linked' because they stay together during independent segregation of chromosomes in meiosis I |
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What are epistatic genes? |
They mask the expression of another gene - epistasis |
