Genetics in Storytelling
By Allison Starkweather
©2001,
Allison Starkweather
Issue # 2: 03/01/01
Visualization
For Writers
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
|
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.
