Question

use the information provided for each family to complete the following:

	family 1	family 2	family 3	family 4

• create a punnett square that illustrates the crosses for each family that provides for the expected outcome of offspring
• determine the genotypes and phenotypes of each of the parents
• determine the phenotypic ratio and percentage of the cubs
• determine the genotypic ratio and percentage of the cubs
• determine the pattern of inheritance

analysis and application:

1. discuss each inheritance pattern and provide an example of a trait that follows this pattern from the gummy bear families
2. compare what the heterozygote looks like for each of the above patterns of inheritance.

Explanation:

Step1: Analyze Family 1

Let's assume B represents the allele for blue and b for light - blue. Since there are 2 blue and 2 light - blue cubs, if the cross is Bb x Bb:
The Punnett square would be:

	B	b
b	Bb	bb

The genotypes of the parents are Bb (heterozygous). The phenotypes of the parents are blue (since B is dominant over b). The phenotypic ratio of the cubs is 3 blue : 1 light - blue (75% blue, 25% light - blue). The genotypic ratio is 1 BB : 2 Bb : 1 bb (25% BB, 50% Bb, 25% bb). The pattern of inheritance is simple dominance.

Step2: Analyze Family 2

Let's assume O is the allele for orange. Since all 4 cubs are orange, if the cross is OO x OO or OO x Oo or Oo x Oo (but since all are orange, the most likely is OO x OO).
The Punnett square for OO x OO:

	O	O

The genotypes of the parents are OO (homozygous dominant). The phenotypes of the parents are orange. The phenotypic ratio of the cubs is 100% orange. The genotypic ratio is 100% OO. The pattern of inheritance is simple dominance (homozygous case).

Step3: Analyze Family 3

Let's assume Y is for yellow and R is for red and they are alleles of the same gene with incomplete dominance. Let the cross be YR x YR.
The Punnett square:

	Y	R
R	YR	RR

The genotypes of the parents are YR (heterozygous). The phenotypes of the parents may be a blend (if incomplete dominance). The phenotypic ratio of the cubs is 1 yellow : 2 blend : 1 red (25% yellow, 50% blend, 25% red). The genotypic ratio is 1 YY : 2 YR : 1 RR (25% YY, 50% YR, 25% RR). The pattern of inheritance is incomplete dominance.

Step4: Analyze Family 4

Let's assume G is for green and P is for purple and they are co - dominant. Let the cross be GP x GP.
The Punnett square:

	G	P
P	GP	PP

The genotypes of the parents are GP (heterozygous). The phenotypes of the parents are green and purple striped (co - dominance). The phenotypic ratio of the cubs is 1 green : 2 green and purple striped : 1 purple (25% green, 50% green and purple striped, 25% purple). The genotypic ratio is 1 GG : 2 GP : 1 PP (25% GG, 50% GP, 25% PP). The pattern of inheritance is co - dominance.

Step5: Answer Analysis and Application 1

• Simple dominance (Family 1): In the gummy bear families, the color of the cubs where blue is dominant over light - blue is an example.
• Homozygous simple dominance (Family 2): The all - orange cubs situation where the orange allele is homozygous dominant.
• Incomplete dominance (Family 3): The color of the cubs where yellow and red blend to give an intermediate color.
• Co - dominance (Family 4): The green and purple striped pattern where both alleles are expressed simultaneously.

Step6: Answer Analysis and Application 2

• In simple dominance (Family 1), the heterozygote Bb has the same phenotype as the homozygous dominant (blue).
• In incomplete dominance (Family 3), the heterozygote YR has a phenotype that is a blend of the two homozygous phenotypes (a color between yellow and red).
• In co - dominance (Family 4), the heterozygote GP has a phenotype where both green and purple are expressed (green and purple striped).

Answer:

For Family 1: Genotypes of parents: Bb, Bb; Phenotypes of parents: blue; Phenotypic ratio of cubs: 3 blue : 1 light - blue; Genotypic ratio of cubs: 1 BB : 2 Bb : 1 bb; Pattern of inheritance: simple dominance.
For Family 2: Genotypes of parents: OO, OO; Phenotypes of parents: orange; Phenotypic ratio of cubs: 100% orange; Genotypic ratio of cubs: 100% OO; Pattern of inheritance: simple dominance (homozygous case).
For Family 3: Genotypes of parents: YR, YR; Phenotypes of parents: blend (if incomplete dominance); Phenotypic ratio of cubs: 1 yellow : 2 blend : 1 red; Genotypic ratio of cubs: 1 YY : 2 YR : 1 RR; Pattern of inheritance: incomplete dominance.
For Family 4: Genotypes of parents: GP, GP; Phenotypes of parents: green and purple striped; Phenotypic ratio of cubs: 1 green : 2 green and purple striped : 1 purple; Genotypic ratio of cubs: 1 GG : 2 GP : 1 PP; Pattern of inheritance: co - dominance.
For Analysis and Application 1: See Step5 above.
For Analysis and Application 2: See Step6 above.