Thumb Crossing in the Cabral Family (pedigree chart)

Legend

Thumb Crossing in the Cabral Family

- Male

- Female

by Chloe Cabral

- married (parents of offspring)

Mariano

Fatima

P Generation (Parents)

Alleles:

H- left thumb on top

h- right thumb on top

Therefore...

HH- left thumb on top (homozygous dominant)

Hh- left thumb on top (heterozygous)

hh- right thumb on top (homozygous recessive)

genotype- Hh (heterozygous recessive)

phenotype- left thumb on top

genotype- hh (homozygous recessive)

phenotype- right thumb on top

genotype

phenotype

We know that the mother's genotype is hh (right thumb on top) and the father's genotype is either HH or Hh (left thumb on top). We can do a test cross to determine the father's genotype. We know that some of the offspring (Luis, Elisa, Filomena, and Joseph) have the genotype hh (right thumb on top) and the other two offspring (Sanza and Mariano) have a genotype that expresses the dominant gene. In order for some of the offspring to have the genotype hh the father's genotype must be Hh. We can see that if any of the offspring express the dominant trait, their genotype must be Hh. Therefore the mother's genotype is hh and the father's genotype is Hh. Luis, Elisa, Filomena, and Joseph all have the genotype hh and Sanza and Mariano have the genotype Hh.

F1 Generation

Sayuri

Filomena

Luis

Sanza

Joseph

Elisa

Margaret

Luis

Joseph

Mariano

genotype- hh (homozygous recessive)

phenotype- right thumb on top

genotype- HH (homozygous dominant) or Hh (heterozygous dominant)

phenotype- left thumb on top

genotype- Hh (heterozygous dominant)

phenotype- left thumb on top

genotype- hh (homozygous recessive)

phenotype- right thumb on top

genotype- hh (homozygous recessive)

phenotype- right thumb on top

genotype- hh (homozygous recessive)

phenotype- right thumb on top

genotype- Hh (heterozygous dominant)

phenotype- left thumb on top

genotype- hh (homozygous recessive)

phenotype- right thumb on top

genotype- Hh (heterozygous dominant)

phenotype- left thumb on top

*Since Luis' genes are not from the Cabral family and all the offspring he has produced have the genotype Hh, we are unable to determine which dominant genotype Luis has because in both circumstances in the test cross with him and Elisa, it is possible to produce offspring with the genotype Hh. You can not determine his genotype using this pedigree chart.*

genotype(s)

phenotype

genotype

phenotype

We know the mother's genotype is Hh and the father genotype is either HH or Hh (both are left thumb on top). If we look at the offspring, we see that one child has the gene hh and the other either has the gene HH or Hh. By doing a test cross for the possible genotypes of the parents we can conclude that both parents must have the genotype Hh because this is the only possible way that two parents who express the dominant gene could produce offspring that expresses the recessive gene. Therefore, both parents have the genotype Hh, Catherine's genotype is hh, and Elizabeth's genotype is either HH or Hh. Since all both circumstances would produce offspring that would express the dominant gene, we are unable to determine what Elizabeth's genotype is.

The father's genotype is hh (right thumb on top) and the mother's genotype is either HH or Hh (both are left thumb on top). By doing a test cross for the possible genotypes of the mother, we find that we can eliminate the possibility of the mother's genotype being HH because out of the four offspring, at least one must have the genotype hh, since Chloe's genotype is hh. Therefore the mother's genotype is Hh and all offspring can either have the genotype Hh (left thumb on top) or hh (left thumb on top). This shows that Kaia and Elijah's genotypes are both Hh.

We know that Margaret (the mother) has the genotype hh since she expresses the recessive gene (right thumb on top) and the father has the genotype Hh since he expresses the dominant genotype (left thumb on top). By doing a test cross, we can see that the only way that their offspring could express the dominant gene is if the offspring's genotype is Hh. Therefore, we can conclude that Sasha's genotype is Hh.

We know that the mother's genotype is Hh and the father's genotype is either HH or Hh (both are left thumb on top). We can do a test cross to determine the genotype of the father and offspring (both of the offspring express the dominant gene). We can determine that in both cases it is possible for the parents to produce offspring that express the dominant gene, however, this is only possible if they have the genotype Hh. Therefore, the mother's genotype is Hh, both of the offspring's genotypes are Hh and we are unable to determine the father's genotype.

F2 Generation

Michael

Kevin

Dustin

Kaia

Chloe

Catherine

Elijah

Ana

Elizabeth

David

Sasha

Kristina

genotype- HH (homozygous dominant) or Hh (heterozygous dominant)

phenotype- left thumb on top

genotype- Hh (heterozygous dominant)

phenotype- left thumb on top

genotype: hh(homozygous recessive)

phenotype: right thumb on top

genotype- hh (homozygous recessive)

phenotype- right thumb on top

genotype- Hh (heterozygous dominant)

phenotype- left thumb on top

*Since Dustin' genes are not from the Cabral family and the offspring he has produced expresses the dominant gene, we are unable to determine which dominant genotype Dustin has because in both circumstances in the test cross with him and Ana, it is possible to produce offspring that expresses the dominant gene (genotype HH or Hh). You can not determine his genotype using this pedigree chart.*

genotype- either HH (homozygous dominant) or Hh (heterozygous dominant)

phenotype- left thumb on top

*since Michael's genes did not come from the Cabral family and he has not produced any offspring, we are unable to determine which dominant genotype he has by using this pedigree chart*

genotype- Hh (heterozygous dominant)

phenotype- left thumb on top

genotype(s)

phenotype

We know that Kristina's genotype is Hh and David's genotype is either HH or Hh (both are left thumb on top). If we look at the offspring's pictures, we see that one child has the gene hh (right thumb on top) and the other either has the gene HH or Hh (left thumb on top. By doing a test cross for the possible genotypes of the parents we can conclude that both parents must have the genotype Hh because this is the only possible way that two parents who express the dominant gene could produce offspring that expresses the recessive gene. Therefore, both parents have the genotype Hh, Lucas' genotype is hh, and Julia's genotype is either HH or Hh. Since both circumstances would produce offspring that would express the dominant gene, we are unable to determine what Julia's genotype is.

We can determine that both parents' genotypes are either HH or Hh because they both express the dominant gene (left thumb on top). We can do a test cross to determine possible offspring in all circumstances. In all four circumstances, there is the possibility of these two parents producing offspring that expresses the dominant gene (left thumb on top), as River does. Therefore we can conclude that we can not determine the parents' or River's genotype through the use of a punnett square. The parents and River all have either the genotype HH or Hh since their phenotype are all left thumb on top.

We know that the mother's genotype is Hh (left thumb on top) and the father's genotype is either HH or Hh (also left thumb on top). We can do a test cross to determine possible genotypes for the parents. In both circumstances, there is the possibility of Ana and Dustin producing offspring that expresses the dominant gene (left thumb on top), as Savannah does. Therefore we can conclude that we can not determine Dustin or Savannah's genotype through the use of a punnett square. Dustin and Savannah both either have the genotype HH or Hh since their phenotypes are both left thumb on top.

F3 Generation

River

Julia

Savannah

Lucas

genotype- hh (homozygous recessive)

phenotype- right thumb on top

genotype- HH (homozygous dominant) or Hh (heterozygous dominant)

phenotype- left thumb on top

genotype- either HH (homozygous dominant) or Hh (heterozygous dominant)

phenotype- left thumb on top

genotype- HH (homozygous dominant) or Hh (heterozygous dominant)

phenotype- left thumb on top