Question

What does the notch gene encode for? How does this cause a lethal mutation in homozygous recessive males and females?

Answer 1

The Notch gene encodes for a crucial developmental protein, with lethal mutations leading to death before birth in homozygous recessive individuals. Dominant lethal mutations, like Huntington's disease, are rarer and may not manifest until after reproductive age, allowing transmission to subsequent generations.

Step-by-step explanation:

Notch Gene and Lethal Mutations

The Notch gene encodes for a protein that plays a critical role in the development and differentiation of tissues during embryonic development. Mutations in the Notch gene can lead to a variety of developmental disorders. In the context of lethal mutations, a recessive lethal allele can cause death before birth when individuals are homozygous. For example, if both parents carry one copy of a nonfunctional allele, they may appear healthy because they have one wild-type allele that compensates. However, if their offspring inherit the nonfunctional allele from both parents, they will have no functioning copies of the gene. Depending on the essential nature of the gene, this can result in failed development, death in utero, or a shortened lifespan if the gene is needed at a later life stage.

Dominant lethal mutations are rarer because they often result in the death of individuals before they can reproduce. One example of a dominant lethal allele is that for Huntington's disease, which leads to nerve cell degeneration but may not manifest until middle age, allowing for the disease allele to be passed to the next generation before symptom onset.

Answer 2

The notch gene encodes for a protein involved in cell differentiation, and lethal mutations can occur if individuals are homozygous recessive for a nonfunctional allele of an essential gene. Recessive lethal mutations lead to a 2:1 genotypic ratio among surviving offspring of heterozygous parents. Dominant lethal mutations like Huntington's disease allow transmission before they manifest.

Step-by-step explanation:

The notch gene is not mentioned specifically in the reference material provided. However, in the context of genetics, it is known to encode for a protein involved in cell differentiation processes.

Regarding lethal mutations, if we consider a recessive lethal inheritance pattern as in the case with some essential genes, a mutation can cause an allele to be nonfunctional. If an individual is homozygous recessive for such a mutation, they lack a functional copy of the gene which can be essential for survival, leading to death before birth or later.

When two heterozygous parents mate, we expect a 2:1 genotypic ratio among surviving offspring because the homozygous recessive individuals will not survive. Dominant lethal mutations, like Huntington's disease, eventually cause death but may not affect individuals until they have reproduced, enabling the mutation to persist in the population.