Question

unattached earlobes are dominant to attached earlobes. cleft chin is dominant to no cleft. parents that are heterozygous for both traits are crossed. determine the ratio of offspring with the described trait to the total number of offspring: unattached earlobes and cleft chin unattached earlobes and no cleft attached earlobes and cleft chin attached earlobes and no cleft

Explanation:

Step1: Analizar la herencia de cada rasgo

• Sea \(E\) el alelo para orejas sin adherir (dominante) y \(e\) para orejas adheridas (recesivo). Sea \(A\) el alelo para barbilla hendida (dominante) y \(a\) para barbilla sin hendir (recesivo).
• Los padres son \(EeAa\times EeAa\).

Step2: Calcular el número de descendientes con cada combinación fenotípica

• Usando la ley de la combinación independiente (tabla de Punnett \(4\times4\)):
• Unattached earlobes and cleft chin (\(E\_A\_\)):
• \(EEAA\), \(EEAa\), \(EeAA\), \(EeAa\) (tienen \(E\) y \(A\)). Hay \(9\) combinaciones (\(1 + 2+ 3+ 3\)) de \(16\) posibles (\(4\times4\)).
• Unattached earlobes and no cleft (\(E\_aa\)):
• \(EEaa\), \(Eeaa\). Hay \(3\) combinaciones (\(2 + 1\)) de \(16\) posibles.
• Attached earlobes and cleft chin (\(eeA\_\)):
• \(eeAA\), \(eeAa\). Hay \(3\) combinaciones (\(1+ 2\)) de \(16\) posibles.
• Attached earlobes and no cleft (\(eeaa\)):
• Hay \(1\) combinación (\(1\)) de \(16\) posibles.

Answer:

• Unattached earlobes and cleft chin: $9:16$
• Unattached earlobes and no cleft: $3:16$
• Attached earlobes and cleft chin: $3:16$
• Attached earlobes and no cleft: $1:16$