Greg is much taller than either of his parents. This is partly because he has inherited ancestral genes that may not have been expressed in either of his parents' phenotypes and partly because the outward expression of height is affected by a multitude of genes that each contribute a small amount. This latter genetic effect is best described as: a. dampening. b. dominant–recessive. c. additive. d. X-linked.

Additive genetic effect is a form of genetic effect that occur as a result of when two or more genes contributes to the final phenotypic expression. It is when alleles of a gene combine to contribute to the summation of their individual effects.

Therefore, the gene effect is additive because many alleles contribute to the effects of Greg tallness.

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pau785 pau785 · Answer 2 · 2021-11-15T00:04:44+01:00

The answer is c: Additive. This effects happens when two or more genes

contribute to the final phenotype. Then the final effect equals the sum of

the individual effects of each gene.

Genes are DNA sequences that code for proteins and these proteins form

the body and thus determine the characteristics of individuals (the

phenotype). Each gene has two alleles, which are inherited one from each

parent (the genotype). Greg has inherited one allele from each parent for

each gene in his body, although in this problem we focus on the gene that

codes for height.

In most cases, when we speak of inheritance of

autosomal genes (those on non-sex chromosomes), we speak of a pattern

of inheritance where one allele can be dominant (always expressed and

masks the effects of a recessive allele) and another can be recessive (only

expressed if there are two of these). For example, if a genotype is Aa being

A the dominant allele, and a the recessive allele, the person would express

the phenotype of the dominant allele. But this is not the case for Greg's

height gene, as it is mentioned that his height is due to the outward

expression of height is affected by a multitude of genes that each

contribute a small amount. It is also not an X-linked inheritance, for the

same reason, because the phenotype is due to the expression of many

genes. And there is no mention of the height gene being on the sex

chromosome. It is not either dampening, because it is the opposite

mechanism, where gene expression is "damped" through different

mechanisms such as mechanism of transcriptional repression.

Greg's height is due to the additive action of genes, a mechanism of

quantitative inheritance such that the combined effects of alleles at two or

more gene loci are equal to the sum of their individual effects.

So, he inherited ancestral genes that may not have been expressed

previously but that have been accumulating in the genomes that are

inherited through each ancestor.

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