In a hypothetical diploid organism, “squareness” of a cell is due to a threshold

Question

In a hypothetical diploid organism, “squareness” of a cell is due to a threshold effect (gene product levels are important): more than 60 activity units of "square factor" per cell produces a “square” phenotype while less than 60 activity units produces a “round” phenotype. square (s) is a gene that controls the synthesis of square factor. The most common allele found in nature is sc. This allele contributes 50 units of square factor, thus, sc homozygotes have 100 units and are phenotypically square. sn is a null allele (no functional gene product made). sn homozygotes are phenotypically round. A final mutant allele, sh, contributes 70 units of square factor. Sh homozygotes have 140 units and are phenotypically square.

a) Describe the expected dominance relationship between sc and sn alleles? Explain your answer. In your explanation, use ALL the terms listed That apply.

b) Describe the dominance relationship between, sh and sn alleles? Explain your answer.

In your explanation, use ALL the terms listed below that apply.

Terms listed: recessive, haploinsufficinet, dominant, haplosufficient, semidominant, codominant

Please help with questions a and b thanks !

Explanation / Answer

a) The phenotype of sc and sn alleles are round as sc can contribute only 50 units of square factors.

So the heterozygote containing sc and sn alleles are round in shape.

Here sn is recessive and sc is dominant.

Here haploinsufficient condition is arising as ‘sn’ is not able to produce the protein product needed for the maintenance of normal phenotype “square”.

b)The phenotype of sh and sn alleles are square as sh can contribute 70 units of square factors.

So the heterozygote containing sh and sn alleles are square in shape.

Here sh is dominant and sn is recessive.

Because of the presence of sh, we can see haplosufficient condition, where the normal working of one allele (sh) is sufficient to maintain normal phenotype (square shape).

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