Extensions of Mendelian inheritance - Lethal alleles

8 important questions on Extensions of Mendelian inheritance - Lethal alleles

What is a lethal allele?

A lethal allele is an allele that has the potential to cause the death of an organism.

When is a gene considered as an essential gene?

A gene is considered as an essential gene when the absence of the protein encoded by this gene results in a lethal phenotype.
An essential gene is a gene that must be present for survival.

What are nonessential genes?

Nonessential genes are not absolutely required for survival, although they are likely to be beneficial to the organism.
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What are conditional lethal alleles?

Condition lethal alleles are alleles that are lethal, but only under certain environmental conditions.

What are temperature-sensitive (ts) lethal alleles?

Temperature-sensitive (ts) lethal alleles are lethal alleles in a particular temperature range.

What are semilethal alleles?

Semilethal alleles are lethal alleles that act only in some individuals.

Why do you think the heterozygote offspring of two Manx cats survives with developmental abnormalities, whereas the homozygote dies?

The heterozygote has one normal copy of the gene, which allows for development to proceed in a way that is not too far form normal. Having two mutant copies of the gene probably adversely affect development to a degree that is incompatible with survival.

What is the age of onset?

The age of onset is the age when symptoms appear.

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