A sex cell with half the number of chromosomes of a normal cell
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Chromosome
A long coiled molecule of DNA
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Gene
A small section of DNA found on a chromosome
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Allele
A different version of a gene
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Dominant
The version of an allele that is always expressed even if there is only one of the allele.
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Recessive
This version of the allele only shows if there are two copies of the recessive allele.
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Homozygous
The two alleles in a gene are the same.
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Heterozygous
The two alleles in a gene are different.
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Genotype
The combination of alleles that you have.
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Phenotype
The observable characteristics of an organism.
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Give examples of characteristics that are controlled by a single gene
Mouse fur colour and red-green colour blindness. Most characteristics are controlled by several genes interacting
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What is cystic fibrosis?
A genetic disorder of the cell membrane, it results in the body producing lots of thick sticky mucus in the air passages and the pancreas.
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What type of allele causes cystic fibrosis?
Recessive
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What is polydactyly?
A genetic disorder causing babies to be born with extra fingers or toes.
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What allele causes polydactyly?
Dominant
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What are the arguments against embryonic screening?
1. It implies people with genetic problems are not desirable; 2. Eventually everyone will want to screen their embryos to pick the best one; 3. It is expensive.
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What are the arguments for embryonic screening?
1. It stops people suffering; 2. It reduces the cost on treating disorders for the government; 3. There are laws to stop it going too far.
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