Spotlight on Students: Mendelian Genetics

The following is a post that features the exemplary work of my Anthropology 102: Introduction to Physical Anthropology students as they tackled the challenges of Mendelian Genetics of Inheritance.  The background of this assignment was that they were tasked with discovery the parentage of a mystery alien individual from a group of alien species, and this post features some of the best analyses of the situation.  

Image of what a Sethmite might look like.  Image from the ScyFy Television Show Face Off, Episode "Serpent Soldiers"

By: Carol Vinger, Anth 102: 1002

                I recently attended the choosing ceremony for Princess Tanith on the planet Apepth as part of the crew of the space exploration vessel SS Adventurer.  The crew and I were invited by King Quetza and Queen Lindi to observe the ceremony in celebration of the Sethmite Princess’ choice of husband, a culturally significant ritual among their people.  Princess Tanith’s two suitors were Lord Phanindra and Bishop Naga.  The ceremony was interrupted by the Royal Family’s wet nurse, who rushed in carrying a nursing infant and claimed the child’s mother was Princess Tanith.  A hostile confrontation ensued among the Royal Family, whereupon Princess Tanith divulged that either of her suitors could have been the father and she was unsure which one.  

            As the crew’s physical anthropologist, I was enlisted by my Captain to attempt to determine the father of Princess Tanith’s child in order to restore peace amongst the Royal Family and the Sethmite people.  I conducted interviews with the Royal Family and each of the potential fathers, as well as with the child’s wet nurse, and I was able to create a genetic profile of possible heterozygous and homozygous allele combinations for the mother and potential fathers (Stein & Rowe 2014: 28-29).  My extensive physical anthropology training had taught me several things that I employed for this assignment, such as the fact that a genotype consists of one hereditary allele contributed by the mother and one hereditary allele contributed by the father to determine the genetic makeup of a specific gene (Stein & Rowe 2014: 28).  Also, a genotype can be homozygous, meaning two of the same alleles, or heterozygous, meaning two different alleles (Stein & Rowe 2014: 28-29).  In addition, a phenotype is the observed characteristic of a specific genotype, and there are dominant alleles that express themselves and recessive alleles do not express themselves unless a dominant allele is absent (Stein & Rowe 2014: 25, 27-28).  From the information I gathered during the interviews and with the use of Punnett Squares, I was able to determine the child’s father by analyzing the dominant and recessive traits for ear shape, hair color, and skin texture among the parties involved (Stein & Rowe 2014: 31). 

            The first trait I analyzed was ear shape.  The child was born with pointy ears, a dominant expression of the allele identified as P.  Lord Phanindra also had pointy ears, but Bishop Naga had rounded ears, a recessive expression of the allele identified as p.  Princess Tanith had pointy ears, as had all of the Sethmite Royal Family going back at least 15 generations. Because of that, I determined that the mother had a homozygous dominant genotype.  It was unknown whether Lord Phanindra had a homozygous or heterozygous dominant genotype, but it was known that Bishop Naga had a homozygous recessive genotype.  I created a Punnett Square for each possible outcome of genetic combinations based on each potential father’s phenotype and was unable to rule out either suitor as the father of the child because either was capable of creating a pointy-eared offspring with the Princess. 

P P P PP PP P PP PP Lord P. Homozygous Dom.

P p P PP Pp P PP Pp Lord P. Heterozygous Dom.

p p P Pp Pp P Pp Pp Bishop N. Homozygous Rec.

           
            The second trait I analyzed was hair color.  The child was born bald, a recessive expression of the allele identified as b.  Princess Tanith had black hair, the most dominant expression of the allele identified as B, but because Queen Lindi had silver hair, a lesser dominant expression of the allele identified as B(s), Princess Tanith had to be heterozygous dominant genotype, either BB(s) or Bb.  Queen Lindi could not have contributed the B allele to Princess Tanith unless the Queen had black hair.  Both Lord Phanindra and Bishop Naga have silver hair, so I was unable to rule out either suitor as the father of the child because they have the same color hair, and I was unable to ascertain whether they were heterozygous or homozygous genotype for the phenotype for silver hair.  What I was able to ascertain was that in order to produce a bald child, each parent must have contributed a b allele, which meant that Princess Tanith was heterozygous dominant genotype for black hair, expressed as Bb, and the father’s genotype must also have been heterozygous for silver hair, expressed as B(s)b. 

B(s) b B BB(s) Bb b B(s)b bb Princess Bb; Lord P. & Bishop N. Heterozygous Silver

            Lastly, I analyzed the trait for skin texture.  The child was born with scaly skin, the most dominant expression of the allele identified as S.  Princess Tanith had smooth skin, a recessive expression of the allele identified as s.  Lord Phanindra had wrinkled skin, a lesser dominant expression of the allele identified as S(w), and Bishop Naga had scaly skin, previously identified as the most dominant expression of the allele S.  Since Princess Tanith’s expression of the trait was recessive, she was only capable of passing on recessive alleles because she had to be homozygous recessive genotype, or ss.  Therefore, I knew the father must pass on the most dominant expression of the allele, or S, in order to produce a scaly child, regardless if the father was heterozygous or homozygous dominant genotype for scaly skin.  A father with the phenotype for wrinkled skin cannot have an allele for scaly skin in his genotype, otherwise he would have scaly skin himself since it is the most dominant expression of the trait.  Given those facts, I was able to rule out Lord Phanindra as the father of Princess Tanith’s child.

S(w) S(w) s S(w)s S(w)s s S(w)s S(w)s Lord P. Homozy- gous wrinkled

S(w) s s S(w)s ss s S(w)s ss Lord P. Heterozy- gous wrinkled

S S s Ss Ss s Ss Ss Bishop N. Homo- zygous scaly

S s s Ss ss s Ss ss Bishop N. Hetero- zygous scaly

S S(w) s Ss S(w)s s Ss S(w)s Bishop N. Hetero- zygous scaly

            The crew of the SS Adventurer was able to gather valuable scientific and cultural information about Planet Apepth and specifically the Sethmite people during the visit.  The Captain had previously warned the entire crew that the Sethmite people were very volatile and prone to violence, so my conclusion regarding the paternity of Princess Tanith’s child needed to be absolutely accurate in order to resolve the conflict, avoid a war, and gain the trust of the Sethmites.  The task to determine the father of Princess Tanith’s child further provided an opportunity to learn about the genetics of Apepth’s inhabitants and also to build an allegiance with the people of Earth.  I presented a detailed report to the Royal Family that supported my conclusion.  Based on the analysis of all of the possible genetic combinations between the mother and each potential suitor, Bishop Naga was the father of Princess Tanith’s child. 

References

Stein, P.L. & Rowe, B.M. (2014). Introduction to Human Evolution and Prehistory.  United

States of America: McGraw Hill Education.

            In-Text Reference: (Chapter 2: The Study of Heredity, pgs. 25-31)

 

Image of what a Sethmite might look like.  Image from the ScyFy Television Show Face Off, Episode "G.I. Joe Oh No"

 By: Bristol Doxey: Anth 102-1001

 

        

Planet Apepth is home to a civilization known as the Sethmites—ritualistic, violent, snakelike creatures. Their leader, King Quetza, and his wife, Queen Lindi, invited the crew of SS Adventurer to watch a ceremony where their daughter, Princess Tanith, would announce which of two suitors, each from a different royal line, she had chosen to be her husband. During the ceremony, a wet nurse entered with a nursing infant, stating that the infant belonged to Princess Tanith. King Quetza, who is prone to violent outbursts, demanded to know who the father of the infant was. Princess Tanith had engaged in the sacred oil ceremony with both suitors which left her unable to know which had fathered the infant. The Captain of SS Adventurer intervened just as the King was about to burst into a violent rage, and suggested that I, a physical anthropologist and crewmember, use simple Medelian genetics to discover which suitor was the father.

            Medelian genetics utilize gene pairs, or alleles, to predict a phenotype, or observable traits (Stein & Rowe, 2014, p. 25). These traits are passed from generation to generation with only slight variations dependent on the alleles passed down from each parent. Allele pairs can be described as either heterozygous or homozygous. A heterozygous pair would have one dominant trait paired with a recessive trait, while homozygous pairs must be either two dominant or two recessive traits (Stein & Rowe, 2014, pp. 28-29). Homozygous pairs are then termed either dominant homozygous or recessive homozygous (Stein & Rowe, 2014, pp. 28-29).

            Using a Punnett Square, which is a “diagram used to calculate the probabilities of the outcomes of a mating,” I will be able to prove the father of the infant (Stein & Rowe, 2014, p. 31). In order to create the Punnett Square, I will use information found in the Palace Library, as well as knowledge shared with me from the wet nurse. I know that there are three physical traits that can be utilized in my scientific investigation—hair color, skin texture, and ear shape. The wet nurse has informed me that pointy ears have prevailed in the royal family for at least 15 generations, and the infant also has pointy ears, so I will not need to use this trait as a definitive trait to find the lineage.

            Among the Sethmites, there are three different skin textures: scaley, which is most dominant; wrinkled, which is recessive to scaley, and dominant to smooth; and smooth, which is completely recessive. King Quetza is scaley skinned, and Queen Lindi has wrinkled skin. Princess Tanith, however, is smooth skinned, which would mean that her skin type follows the Principle of Independent Assortment, meaning that different alleles were passed to her from her parents independently so that a new combination was formed even though the trait was not present in either parent (Stein & Rowe, 2014, p. 27). Lord Phanindra has wrinkled skin, and Bishop Naga has scaley skin. With what we know about skin type dominance we can create Punnett Squares to predict which skin type the offspring would have.

     We can use the same Punnett Squares to predict from either possible father because both potential fathers have dominant skin type compared to Princess Taniths’ homozygous recessive skin type. In the first square, we assume that either male would have a dominant homozygous skin type, which is written as “SS”, and in the second square we assume that each could be heterozygous. The male genotypes, or the “genetic constitution of an individual” are depicted on the top line of the square while Princess Taniths’ genotype is shown on the left side of the square (Stein & Rowe, 2014, p. 28). Though each possible father has a dominant phenotype of skin texture, Lord Phanindra has wrinkled skin, and Bishop Naga has scaley skin, which is important in the solving of the Punnett Square because the infant has scaley skin. Though wrinkled skin was written as a dominant in the Punnett Squares, it is recessive to scaley skin, so unless Princess Tanith had a scaley skin trait, the father must have passed on this phenotype. I am certain that Princess Tanith did not have a scaley skin trait to pass on because, as was stated earlier, her smooth skin follows the Principle of Independent Assortment since her father, King Quetza, has scaley skin, which is a dominant trait, and her mother, Queen Lindi, has wrinkled skin, which is dominant to smooth but recessive to scaley. Both of her parents’ skin types are dominant to smooth, and provide no explanation to how Princess Tanith has smooth skin. This recessive homozygous trait would not show with either of the possible fathers’ genotypes, rather it would allow the fathers’ trait to become the phenotype of the infant.

            Utilizing simple Mendelian genetics, I have discovered that the infant was fathered by Bishop Naga. The Punnett Squares used show that the Bishops’ dominant skin type, either heterozygous or dominant homozygous, would provide the scaley skin phenotype of the infant. Because Princess Tanith has a recessive homozygous trait, the dominant trait from the father would be expressed, and since Lord Phanindra is wrinkle skinned, it cannot be that an infant fathered by him would have an expressed scaley skin.

Works Cited

Stein, P. L., & Rowe, B. M. (2014). Introduction to Human Evolution and Prehistory. McGraw-Hill Education.