Spotlight on Students: Mendelian Genetics

The following is a post that features the exemplary work of one of my Anthropology 102: Introduction to Physical Anthropology students.  In this assignment he was tasked with addressing a problem involving Mendelian Genetics of Inheritance.  The background of this assignment was that students were tasked with discovery the parentage of a mystery alien individual from a group of alien species. 


Murdoc Brickel, Anth 102: 1001

Field report from planet Phelineas to Captain of SS Adventurer:

Include: Phelineas Royal family:

SUBJECT: Concerning the fatherhood of Katze newborn of Princess Silina.

            In the question of who sired the newborn baby of Princess Silina I have determined who has become the father through the sacred oil ceremony.  Through the process of deductive reasoning, and using the techniques of simple Mendelian genetics I can prove who sired the new born.  Using the resources of the Royal Family Library I was able to build a database of enough information to determine easily identifiable physical traits and their orders of dominance,  which is a characteristic of genetics that determines which traits, or alleles, will be physically shown (Stein & Rowe,  2014, pg. 25).  The traits that I will be using are the pointedness of the ears, the color of hair, and the texture of the skin.

            First I will describe the basis of the process by which I used to determine the father, then I will present the evidence to support my decision.  The process of Mendelian genetics studies the pairing of two alleles, with one usually being more predominant over the other when they are physically expressed.  This physical expression is called the phenotype (Stein & Rowe, 2014, pg. 28).  I have enclosed charts after this report which will show in detail how this bonding process results in a combination of possible outcomes given the genetic information of the parents.  When one gene is considered dominant over another the dominant trait is the trait that will be shown.  In the case of a recessive gene, or a gene that is less dominant, it takes a pairing of both of these recessive genes for the trait to become visible (Boston, C., Dr.; Lecture).      All dominant traits are expressed in the charts following with a capital letter, for example 'A'.  All recessive genes are expressed with a lower case letter for example, 'a'.  There are certain traits that are less dominant than others, and more dominant than others.  For example, let us say that trait 'B' is more dominant than trait 'a', but less dominant than trait 'C'.  If we were to arrange these three traits in their order of dominance for greatest to least it would look like 'C-B-a' , so in pairing the 'C' and 'B' genes together 'B' would be the recessive gene.  This would be written as 'Cb”, and the 'C' gene would be expressed (Boston, 2015, Lecture).

            Now I will discuss the issue of the ears, or how pointy or rounded they are.  Through research in the library, I have determined that pointy ears have a dominance over the trait for rounded ears.  Through speaking with the wet nurse (Wet Nurse, Interview) I was able to determine that the Princess was a homozygous carrier of the pointy ear trait.  What this means is that both sides of the family in the Royal Family of Phelineas had pointy ears.  When it is said that someone is a homozygous carrier of a trait, it means that both of their alleles for a gene are of the same type (Stein & Rowe, 2014, pg. 28).  Since the pointy ears alleles are dominant, we could also refer to the Princess as a homozygous dominant carrier.  Since both of her alleles for this trait are dominant, and she has two of them, she could not have children without pointy ears.  This is why this trait, while it is a good point of reference that is easy to identify, would not be a good judge of who the father is.  I was not aware of this factor when I was doing my research in the library.  I have included it in this report as a point of reference, as any future children that the Princess may have with either of these suitors may have rounded ears.  This is due to a blending of the alleles, which is referred to as a heterozygous carrier.  This is another big word that basically means that an individual would have a dominant and a recessive allele present in their genetic makeup (Stein & Rowe, 2014, pg. 29). 

            Let us move now to the hair genes.  As we have seen, the baby is bald.  According to my research in the Royal Family Library, this is not just because it is a new born.  As you know Katze children are born with hair, if they will have it.  This baldness is what would be referred to as a homozygous-recessive gene.  This means that the child would need two of the same recessive allele in order to have this phenotype.  This occurred because both of the parents were carriers for the baldness allele, or heterozygous with a baldness allele.  The Princess has black hair, which I have found to be the most dominant of the three hair traits.  She has a bald child so she is a carrier of the baldness allele.  The potential fathers both have silver hair.  The silver haired allele I found is less dominant than black hair, and more dominant than baldness.  The chances of the Princess and one of the suitors having a bald headed child are among the rarest but not out of the realm of possibilities.  Since both of the potential suitors have silver hair, we can rule this out as a determining factor as to who sired the child.  Again, I include this as an explanation.  Even though none of the potential partners are bald, as the baby is, this does not mean that they would not be the parents.  This means that the Princess and one or both of the suitors more than likely had a bald relative and have passed this trait down to the infant.

            Now we will move onto the skin texture.  I have noticed that there are three distinct skin types among the Katzes, which are smooth, wrinkled, and scaly; these are presented in their order of dominance from least dominant to most dominant.  The Princess has smooth skin, which is a homozygous recessive genotype, or that she could only have this skin type allele.  Lord Garpheldhas a wrinkled skin type, which means that while he may also be a carrier for a smooth skin type gene he does not have a scaly skin type gene.  Bishop Pheelex, on the other hand, does posess a scaly skin type.  This skin type gene I found to be the most dominant among the three skin types.  This means that if it were present, it would be physically expressed, which leads me to say that Bishop Pheelex is the father of the child.  As a post note, if the Bishop and the Princess were to have more children, they may also have children wrinkled or smooth skin.  This is because the Bishop may be a heterozygous carrier of these genes, and with the Princess having the most recessive of the group any other trait would take dominance with regards to skin type (Boston, 2015, Lecture).

            In conclusion, Bishop Pheelex is the father of the baby.  The Princess' homozygous dominant pointy ear alleles mean that any child she has would also have pointy ears.  The baby’s baldness is a result of both the Princess and Bishop Pheelex being carriers of the bald allele.  The scaliness of the baby’s skin comes from his father Bishop Pheelex as this is a dominant gene.  Something to keep in mind is that the Princess's baby may have children with rounded ears.  Another thing to keep in mind is that if the Princess and the Bishop have another child it may have hair and a different skin type than this baby.  May prosperity always find the Royal Family of Phelineas.

Punnett Squares

 Highlighted pairs reflect what the baby has

Ear Shape –R=pointy r=rounded

HOMO	Lord Garpheld
Princess Silina	R	R
R	RR	RR
R	RR	RR

HETERO/HOMO	Lord Garpheld
Princess Silina	R	r
R	RR	Rr
R	RR	Rr

HETERO/HOMO	Bishop Pheelex
Princess Silina	r	r
R	Rr	Rr
R	Rr	Rr

Phenotype 100% pointy ears

Hair – B=black S=silver b=bald

Since both Lord Garpheld and Bishop Pheelex have silver hair, the comparisons will be the same for both.

HOMO	Lord Garpheld/ Bishop Pheelex
Princess Silina	S	S
B	Bs	Bs
B	Bs	Bs

HETERO/HOMO	Lord Garpheld/ Bishop Pheelex
Princess Silina	S	b
B	Bs	Bb
B	Bs	Bb

HOMO/HETERO	Lord Garpheld/ Bishop Pheelex
Princess Silina	S	S
B	Bs	Bs
s	SS	SS

HETERO/HETERO silver	Lord Garpheld/ Bishop Pheelex
Princess Silina	S	b
B	Bs	Bb
s	SS	Sb

HOMO/HETERO bald	Lord Garpheld/ Bishop Pheelex
Princess Silina	S	S
B	Bs	Bs
b	Sb	Sb

HETERO/HETERO bald	Lord Garpheld/ Bishop Pheelex
Princess Silina	S	b
B	Bs	Bb
b	Sb	bb

Black Hair 67%  Silver Hair 29%  Bald 4%

Skin Type – S=Scaley  W=Wrinkled  s=smooth

HOMO/HOMO	Lord Garpheld
Princess Silina	W	W
s	Ws	Ws
s	Ws	Ws

HETRO/HOMO	Lord Garpheld
Princess Silina	W	s
s	Ws	ss
s	Ws	ss

HOMO	Bishop Pheelex
Princess Silina	S	S
s	Ss	Ss
s	Ss	Ss

HETERO Wrinkled/HOMO	Bishop Pheelex
Princess Silina	S	w
s	Ss	Ws
s	Ss	Ws

HETERO Smooth/HOMO	Bishop Pheelex
Princess Silina	S	s
s	Ss	ss
s	Ss	ss

Scaled skin 40%   Wrinkled skin 40%  Smooth skin 20%

Bishop Pheelex is the father of the child.

References

Boston, C. , Dr. (Director) (2015, January 27- May 13). Physical Anthropology. Lecture conducted from Truckee Meadows Community College .

Stein, P., & Rowe, B. (2014). Physical anthropology (Eleventh ed.). McGraw-Hill.

Wet nurse to Phelineas Royal family [Personal interview].(n.d.)

Phelineas Royal family personal library.