Genetics in Storytelling

By Allison Starkweather

2001, Allison Starkweather  

Issue # 2: 03/01/01


Visualization For Writers
Feature Articles
Creating and Using Language in Fiction
By Damon M. Lord
A, B, C: Beith, Luis, Nin
By Bryn Neuenschwander
Genetics in Storytelling
By Allison Starkweather
Creating Character Extras to Enhance Your Story
By Shane P. Carr
At a Loss for Words
By Vicki McElfresh
The Alternative Rules
By Lazette Gifford
Fantasy: 
A Man in Beast's Clothing
By Sarah Jane Elliott
Horror: 
What Is Horror?
By Teresa Hopper
Poetry: 
How-to Haiku
By Jennifer St. Clair Bush
Romance: 
Research Flaws in Romance Novels
By Anne M. Marble
Science Fiction: 
Tuning the Universe
By Bob Billing
Stage & Screen: 
The Dual Landscape of Plot and Story
By Robin Catesby
Suspense & Mystery:
Scene of the Crime
By Shane P. Carr
Young Adult & Children:
A Question of Style
By Justin Stanchfield
Young Writer's Scene:
Befriending the Internal Editor
By Beth Adele Long
Book Reviews
The Writing Life by Annie Dillard
Reviewed by Beth Adele Long
Web Site Reviews
The Forward Motion Web Site
By Lazette Gifford
Helpful Pointers for Community Members
By Jim Mills
From the Writers' Board
News from Forward Motion

 

What you don't want is the kind of description that turns up in police reports: "Caucasian male, twenty-seven years old, six feet, 170 pounds, short brown hair, blue eyes." . . . Such a description has detail, all right, but not the right detail.

Nancy Kress
Dynamic Characters
1998
Writer's Digest Books
ISBN: 0-89879-815-9

 

Genetics can play an important part in a story. It affects how everyone and everything looks; your characters, their parents, their children, their cats, dogs, horses, and the potted flower sitting on their front porch. It can help your story, by giving it an extra touch of realism, or hurt it, by being completely unbelievable.

Organisms can reproduce one of two ways—sexually or asexually. When they reproduce asexually, there is only one parent, and the offspring are genetically identical to the parent. However, most organisms reproduce sexually, where two parents are needed and they each give the offspring half of their chromosomes.

Genes are the sections of DNA that tell what a specific trait, such as hair color, will be like. For most traits, there are two different alleles, or variants of that trait, which are either dominant or recessive. If an allele is dominant, then it will always be the one expressed, even if the organism also has a recessive allele for that trait. The only way a recessive trait can be expressed is if both alleles are recessive. Because of this, it is possible for two people who show dominant alleles to have a child who expresses the recessive allele, if they both carry the recessive allele and the child receives one copy of it from each parent.

Though you can never be completely sure what a child will look like, there are laws of inheritance that you can use to find the probability of the child's expressing or carrying a certain trait. One of the tools you can use to help you is called a Punnett square.

       __ __ (parent # 1)
      
_____
__   |__|__|
__   |__|__|
^
 
|(parent # 2) 

To use the Punnett square, you put the alleles of one parent along one side, and the alleles of the other parent along the other side, with one allele in each blank space. Dominant alleles are written with capital letters, and recessive alleles are written with lowercase letters. Next, you combine the alleles in the boxes, so you can see all of the possible combinations. For example, if you wanted to know if your character’s child could have a widow’s peak (a dominant trait), and what the chances of that would be, you could the Punnett square. If the mother did not have a widow’s peak (which means her alleles would have to be rr), but the father did, and his alleles were Rr, then we could stick them into the Punnett square: 

         r     r (mother)
        
_____
R__  |Rr|Rr|
r__   |rr |rr  |

(father)

 

So, you can see that the child has a fifty percent chance of having a widow’s peak, and a fifty percent chance of not having one. A Punnett square shows you the possible genotype of the offspring; their genetic make-up. From this you can determine the phenotype; what physical characteristics the child has.

Up until now, we’ve been assuming that all alleles are either dominant or recessive, but that is not always true. There are several types of intermediate phenotypes, two of them being incomplete dominance, and polygenic traits. Incomplete dominance is where, rather than one allele completely blocking out the other, the two alleles form a combined phenotype. One example of this is the snapdragon; if a snapdragon receives a red allele and a white allele, rather than being only one of them, the alleles blend, and the flowers will be pink. This does not mean that the alleles blend, however. The flower still has one white and one red allele, not two pink alleles. An example of this in humans is hair type; curly hair and straight hair combine to form wavy hair.

Another form of incomplete dominance is polygenic traits. That’s where more than one gene controls a single trait. An example of this is eye color. This trait is controlled by three genes; one for the color of the pigmentation in the iris, one for the darkness of the color, and one for the distribution of color that creates the patterns in our irises. Polygenic traits are much harder to predict than monogenic traits.

Other factors in inheritance are multiple alleles. Some genes have more than two alleles. They could have three, four, or more. Pleiotropy is also a factor. Pleiotropy is the opposite of polygenic traits. It is where more than one trait is controlled by one gene. This is the only instance where traits are linked, and inheriting one means you must inherit the other.

Environmental effects can also be important. Climate can play a major part in determining an organism’s phenotype. In some organisms, such as the Siamese cat, the fur color is determined by temperature, which is why the cat’s ears, nose, paws, and tail are darker than it’s body: because they are farther from the body, their temperature is cooler. Social environment can also stimulate changes. Some fish can, if all of the males die, change their sex from female to male. If a new male shows up, they can then return to female form.

 All of this information can help when writing your story. If a character gets pregnant, is it possible for the child to look a certain way, even if the parents don’t show any of those traits? Do your characters’ parents have to look a certain way, in order for the character to have turned out the way he or she did? Also, if you’re writing fantasy or science fiction and create your own beasts, it can be incredibly useful in helping you decide how traits are inherited. Perhaps your stories include dragons. Are certain colors linked to the dragon’s size? If it has horns or a neck frill, can they be different sizes, or are they either there or not? These are all questions to think about, not only when creating a new species or deciding to get a character pregnant, but also when creating any type of family.

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