Skin color in a certain species of fish is inherited via a gene with four different alleles. Each allele confers a unit of color darkness such that having allele S1 confers one unit of color, S2 has two units, S3 has three units, and S4 confers four units. A fish of this type has the genotype S1, S3, and its mate has the genotype S2S4. What proportion of their offspring would be expected to have five units of color

25% of the progeny with genotype S3S4 is expected to express 5 units of color

Explanation:

Available data:

Cross:

Parentals) S1 S3   x   S2S4

Gametes) S1   S3      S2     S4

Punnett square)       S1           S3

                      S2     S1S2      S2S3

                      S4     S1S4      S3S4

F1) 1/4 = 25% of the progeny is expected to be S1S2, expressing 3 units of color ⇒ allele S1 provides one unit, allele S2 provides two units of color

    1/4 = 25% of the progeny is expected to be S2S3, expressing 5 units of color ⇒ allele S2 provides two units, allele S3 provides three units of color

    1/4 = 25% of the progeny is expected to be S1S4, expressing 5 units of color ⇒ allele S1 provides one unit, allele S4 provides four units of color

    1/4 = 25% of the progeny is expected to be S3S4, expressing 7 units of color ⇒ allele S3 provides three units, allele S4 provides four units of color

25% of the progeny with genotype S3S4 is expected to express 5 units of color

it has to be understood that the sea water contains a huge amount of sodium and chlorine ions and if they enter the cell of the atlantic cod fish, the cell will shrivel and the fish will die. to avoid such a condition, the fish uses active transport for the purpose of removing the ions against the gradient.

explanation:

the atlantic cod is not a maritime osmoconformer. its native application of salts is less than that of the seawater it lives in. it is continually falling water from the gills to the ocean via osmosis.

countering that, the fish is going to be swallowing seawater. but since its internal collection of salts is lower than seawater, the fish will want to go free of excess salt, and since that's going upon a gradient, then active transport, requiring energy, must be used to pump out the salt. much marine fish use the organs to filter out the salt and these fish discharge very straight urine.