Question

multiple select question
select all that apply
scientists have identified almost 2000 loss-of-function (lof) alleles that can exist as homozygotes in humans. what is true of these lof alleles?

they are very important, as they seem to represent mostly genes important for embryonic development.
they are relatively common in humans.
they are found at very low frequencies.
they are thought to represent nonessential genes with unknown functions.

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Explanation:

Loss-of-function (LOF) alleles that can exist as homozygotes in humans are unlikely to affect essential genes (like those for embryonic development, as homozygosity for such LOF would be lethal). They are typically nonessential genes (often with unknown functions) and are found at low frequencies because even nonessential LOF may have mild fitness costs. They are not relatively common.

Answer:

C. They are found at very low frequencies, D. They are thought to represent nonessential genes with unknown functions