Sex Linked Traits

Figure 1: Genetic Inheritance of X Chromosome Sex Linked Conditions (Source: Boundless, 2019)

Today’s blog post is dedicated to expanding on previously discussed Mendelian genetic content, specifically addressing sex-linked genetic inheritance.  Prior to reading this post it is important that you have the appropriate background to understand this post’s content.  You will need an understanding of Mendelian genetics, dominant and recessive alleles, as well as how genetic inheritance is understood through Punnett Squares.  If you do not already understand these terms or have the required background please click on the hyperlinks provided in the previous sentence so you can read and catch up on these topics. 

 

Sex linked traits are genes present on a sex chromosome (typically the X or Y chromosome).  These chromosomes are often referred to as the sex chromosomes because they determine the sex of individuals.  Males carry one X and one Y chromosome, whereas females carry two X chromosomes.  These chromosomes not only determine biological sex of the individual, but they also genetically affect the individual in other ways since both chromosomes carry genetic information.  The X chromosome, which is larger, carries approximately 1098 genes, while the smaller Y chromosome carries 26 genes, which largely relate to sperm production and other nominal activities.   

 

There are a variety of X linked genetic conditions out there.  These include but are not limited to hemophilia, red-green color blindness, congenital night blindness, some high blood pressure genes, Duchenne muscular dystrophy, and also Fragile X syndrome.  Women can either display/present with these conditions or they can be carriers, the latter of which results in them having (or carrying) one recessive allele (or copy) of the gene, but men will always express the X chromosome genetic condition since they only carry one X chromosome. 

 

Males receive their X chromosome from their mothers (a result of the fact that be born a male their father’s must provide the Y chromosome), which in turn explains why X chromosome conditions in males are often blamed on the mother.  Since males only carry one X chromosome they are forced to express whichever allele of the gene (be it dominant or recessive) is present on the X chromosome.  This means that males have a 50/50 chance of expressing either a dominant or recessive allele for X chromosome conditions, while women do not (Figure 1).  Due to the presence of a Y chromosome in males they are the only individuals who can carry and pass on Y linked genes.  Y chromosome conditions can only be present in females if and when they carry the Y chromosome, which is typically a third copy of a chromosome.

 

References

Boundless. (2019, November 19). 12.2E: Sex-Linked Traits . Retrieved from Biology: Libre Texts: https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book%3A_General_Biology_(Boundless)/12%3A_Mendel%27s_Experiments_and_Heredity/12.2%3A__Patterns_of_Inheritance/12.2E%3A_Sex-Linked_Traits

Easter, C. (No Date). Sex Linked. Retrieved from National Human Genome Research Institute: https://www.genome.gov/genetics-glossary/Sex-Linked

O'Neil, D. (2012). Sex Linked Genes. Retrieved from Palomar Anthropology Biology Basics: https://www2.palomar.edu/anthro/biobasis/bio_4.htm

We're Different; We're the Same: Cultural Universals, Generalities, and Particularities

Figure 1: Various Types of Family Units (Far Left: Nuclear Family; Middle: Extended Family; Far Right: Same Sex Parents Family; Image Sources: Google Images)

Today's blog post will be an extension of a previous post about culture, in which the elements of what is considered part of culture and how culture affects our daily interactions and thinking were explored.  While cultures around the globe are unique there are actually quite a bit of similarities among all human groups.  These similarities do vary by type, and today's blog post will be exploring these further by addressing cultural universals, generalities, and particularities.

Cultural universals are aspects of culture that exist in every culture.  This means that there are certain components of cultures that are the same, which are the result of human biological and cultural needs.  These needs necessitate these basic and key aspects of culture that is present in all cultures around the world.  For example, all humans have to eat, so every culture has some sort of food sharing system in place.  Additionally, in order for the human species to continue to exist there needs to be some reproduction, and attached to that and due to the extended infant dependency period among human children there are family units (Figure 1).  These family units also account for satisfying the human social need to be integrated into groups and consistently surrounded by people.

While these cultural universals are present in every cultural group it does not mean that they will manifest the same way.  This is where cultural generalities come in, a term that is defined as cultural patterns that vary by culture, being present in some but not all.  Let's look again at the cultural universal of the family unit.  Every culture has family units with them (again, an example of cultural universals), but what the family unit looks like will vary.  Some cultures acknowledge a nuclear family unit where only the parents and children are considered a family unit, whereas some cultures promote the extended family unit, in which the parents and extended family (e.g. grandparents, aunts and uncles, and any associated cousins/nieces/nephews) are one family unit (Figure 1).  Some cultural groups will also acknowledge family as only being on either the mother's (matrilineal) or father's (patrilineal) side, meaning members of either parent's family are acknowledged as family, while the other parent's family is not.  There can also be ambilineal descent, where both parents' family is identified as family, too.  Then there are matters of who can get married and start a family, with many cultures only recognizing heterosexual family units and some, such as American and Canadian cultures, that recognize homosexual families (Figure 1).

Lastly, there are some aspects that are unique to only one or a few cultures.  These are known as cultural particularities.  These aspects of culture are often so unique and different from other cultures that they require their own classifications and discussions.  Examples of cultural particularities are acts of cannibalism (e.g. among the Fore), head hunting traditions (e.g. among the Jivaro), and sometimes even unique cuisine.  Again, these are elements of culture that are unique to only one or very few cultures and are not considered the norm across all cultures.  The uniqueness of these traditions or customs are often accounted for through various culturally specific needs that often can be linked back to universal aspects of what it means to be human but the manifestation of that need is specific to the culture practicing it.

References

Gezon, L., & Kottak, C. (2014).  Cultural Anthropology McGraw-Hill

 

This is One Corny Post: The Domestication of Maize (Corn)

 

Figure 1: Comparison of teosinte and modern corn (Image Source: Nicole Fuller, National Science Foundation)

Corn is a very versatile crop used in various food products (e.g. flower, starch, syrup, etc.), ethanol (fuel), livestock feed, and even, in some cases, plastic production.  Thousands of varieties of corn are grown across the globe, thereby making it a primary cash crop and source of income for people everywhere.  It is also a staple of many people’s diets, making it a great and necessary nutritional resource, too.  What you may not know is that corn is also a great example of artificial selection, which refers to situations were organisms are intentionally bred for desired characteristics.  Today’s blog post will explore the origins of corn, and why it is important to understand its evolution.

 

Corn, or more commonly referred to as maize in the archaeological literature, is not a naturally occurring product in the environment.  It was actually derived from a plant known as teosinte (Figure 1).  Teosinte is a natural grass common throughout the Americas, and it produces a fruit that has a very small, slender cob and thick, almost impenetrable husk.  There are many variations within the teosinte plant species, which made it a perfect plant to work with among early human agriculturalists.  It is unclear what specifically led these individuals to artificially select and breed specific teosinte plants, but their work, which began almost 9000 years ago in southern Mexico, paid off.  They turned this unappetizing plant into a dietary staple not just for peoples of the Americas but the world.

 

Figure 2: Examples of Various Types of Corn (Image Source: Popcorn.com)

Archaeologists were able to track the evolution of teosinte into modern day corn through various archaeological discoveries throughout Central and South America.  Early evidence noted specific changes in size and shape of early teosinte plants found in refuse spots (i.e. middens or trash heaps), along with evidence of consumption of the kernels.  Over time and with the advancement of paleogenetic work scholars were able to track the molecular evolution of this plant.  This led to a more recent and revolutionizing discovery, which showed that corn underwent several evolutions.  The first began in Mexico, and then subsequent domestication and evolution events occurred 6500 years ago in the western Amazon region.  Peri-domesticated corn was either sent or brought to the region and adopted into the agricultural exploits of the region.  The corn grown here was actually domesticated before the corn in its place of origin in Mexico, which accounts for the various types of corn that exists today (Figure 2). 

 

This information not only provides us insights into the artificial selection patterns and evolution of corn but also into the prehistory of human populations of South America.  Archaeological evidence demonstrates that whenever corn started being grown in a region it was the direct result of human migration to the area.  Corn is very dependent on humans to grow it, care for it, and harvest it, which is also very important in understanding how to maintain it in rapidly changing environments that exist today.  By understanding the human relationship with the evolution of corn one can better comprehend and initiate future changes in various other staple crops, which could help prevent crop loss, extinction, and food shortages.

 

Bibliography

Bower, B. (2018, December 13). Corn domestication took some unexpected twists and turns. Science News.

Katz, B. (2018, December 14). Rethinking the Corny History of Maize. Smithsonian Magazine.

Mangelsdorf, P. C., MacNeish, R. S., & Galinat, W. C. (1964, February 7). Domestication of Corn. Science Magazine, pp. 538-545.

Smithsonian. (2018, December 13). Scientists overhaul corn domestication story with multidisciplinary analysis. Retrieved from Phys.org: https://phys.org/news/2018-12-scientists-overhaul-corn-domestication-story.html

Tian, F., Stevens, N. M., & Buckler IV, E. S. (2009). Tracking Footprints of Maize Domestication and Evidence for a Massive Selective Sweep on Chromosome 10. National Academy of Sciences.

 

Collateral Damage: The Impacts of the Covid-19 Pandemic on Endangered Languages

It is plain to see that the Covid-19 Pandemic has had a great deal of affects on humans across the globe, from altering social interactions to the devastating losses of life.  While much focus has been placed on understanding the virus and preventing its spread there has also been calls for attention on the latent affects of this virus, particularly on endangered languages.  Today’s blog post will explore the impacts of the Covid-19 Pandemic on endangered languages and what this means for the great whole of humanity across the globe.

 

Endangered languages exist across the globe.  These include languages that have few native speakers, are no longer taught (or infrequently taught), and/or is hardly spoken regularly.  Endangered languages are classified by risk of loss, from endangered to critically endangered, and they are considered extinct when no native speaker or speakers remain alive.  Several efforts have been undertaken to preserve endangered languages, and until recently these efforts were inconsistently effective.  With the Covid-19 Pandemic, though, several of these efforts have been halted as a result of mandatory quarantines, social distancing measures, and fears of spreading the virus.  Furthermore, individuals who were willing to teach and those willing to learn endangered languages have had their attentions directed elsewhere, or they have been physically isolated from each other, further hampering language preservation efforts.

 

The loss of endangered languages carries serious consequences outside of just losing the language itself.  Languages are key elements of culture, and endangered language speakers often hold cultural and historical knowledge that will also be retained with the preservation of the language.  Information critical to appropriately conserving and using natural resources, fighting past pandemics, and other important cultural knowledge is being lost as a result of the Covid-19 virus claiming the lives of endangered language speakers.  The historical and cultural knowledge loss is accompanied with great loss of human life, a fact that should not be hastily overlooked.

 

Additionally, the Covid-19 Pandemic has highlighted disparities in access to health care among indigenous populations, particularly those who retain the crucial cultural, historical, and linguistic knowledge.  Speakers of endangered languages often do not speak the dominant language, and they then cannot access accurate information about the virus and preventative measures to help them avoid catching it.  Those who do speak another language are often shut out of conversations and information dissemination campaigns about Covid-19 and preventative measures as medical workers and others governmental agents do not think or consider sharing this information with these vulnerable populations.  

 

The health care issues are the not the only ones faced by endangered language speakers and their kin.  Many members of these groups already live in poverty and are faced with greater economic challenges as they cannot continue their livelihoods due to the quarantine and/or social distancing efforts meant to stave off the spread of the virus.  There are also issues of outsiders taking resources away through the willful theft of lands and resources from these groups, many of whom are willingly self-isolating in order to protect themselves and their cultures.

 

Ultimately, the Covid-19 Pandemic has emphasized various areas of economic, health, and social disparities among societies and cultural groups globally, particularly focusing on issues faced by endangered language speakers.  Several efforts have been initiated to not only bring attention to these matters but also work to resolve them.  I am hopeful that such efforts will accomplish substantive changes that lead to more equitable societies, but one first must be aware of these issues before such goals can begin to be worked toward.

 

References

Abbi, Anvita. "The Pandemic Also Threatens Endangered Languages." Scientific American 20 April 2020. Electronic.

Drude, Sebastian. "The direct and indirect impact of Covid-19 on people speaking endangered languages in Brazil." 24 April 2020. FEL Blog. Electronic. 16 June 2020.

Fernandes, Aaron. "Coronavirus could have a devastating impact on endangered languages." SBS News 5 March 2020. Electronic.

UNESCO. COVID-19 Pandemic: Language matters. 2020. Electronic. 16 June 2020.