DRAGON GENETICS

One of the first steps used to study how traits are inherited is to design a key. Using the letters of the alphabet, simply select a letter to symbolize the trait you are investigating. For example, you might want to use the letter “n” to symbolize the length of the dragon’s neck. Remember that each trait is expressed independently, unless it happens to be connected or linked to another trait, such as in the case of a sex-linked gene. The sample key below shows some typical genetic traits or characteristics of dragons.

Dragon Genetics Key
Upper case letters represent dominant alleles. (One required for trait to be expressed.)
Lowercase letters represent recessive alleles. (Two required for trait to be expressed.)
C = FOUR CLAWS
c = three claws
E = YELLOW EYES
e = red eyes
F = FIRE BREATHING
f = not fire breathing
H = HORNS
h = no horns
N = LONG NECK
n = short neck
S = SCALES
s = no scales (smooth skin)
T = TAIL SPIKES
t = no tail spikes
W = LARGE WINGS
w = small wings
* Codominant Traits *
R = RED BODY COLOR
B = BLUE BODY COLOR
G = GOLD BODY COLOR

Mixed colors = Purple, Green, Bronze
L = FOUR LEGS
l = no legs

Mixed traits = Two Legs
* Sex-linked Genes *
X = X chromosome / no ear frills
(XX = female)
Y = Y chromosome / ear frills
(XY = male)

The upper case version of the letter you choose represents the dominant allele for the trait; the lower case version of the letter represents the recessive allele for the trait. An allele is one of the two or more alternative forms of the same gene or segment of DNA on a chromosome. Each allele carries the genetic information that codes for specific traits (for instance, the neck length gene for our dragon). Each allele from one parent will pair with an allele from the other parent, to create a complete code for a specific genetic trait. An allele is dominant when it completely masks the presence of the allele it is paired with. The trait that is hidden or masked is the recessive trait. Therefore, the recessive form would only be expressed when two of the same alleles are present.

Suppose that in our hypothetical dragon, long necks are dominant to short necks. If a baby dragon inherited even one long neck allele (N) from either parent, the baby would have a long neck. Since the most simple inheritance patterns involve transmission of one trait from the mom and one trait from the dad, all “NN” and “Nn” dragons would have a long neck. The only letter combination that would represent a short-necked dragon would be “nn”. This would mean both the mom and the dad contributed one recessive, short neck allele (n) during the fertilization process.

INSTRUCTIONS: Refer to the “Dragon Genetics Key” provided, and answer the following questions regarding dominant and recessive alleles.

1. What letters are used to represent wing color? _____________________________________
2. What letters are used to represent neck length? _____________________________________
3. The letter “Y” is used as a symbol to represent _____________________________________
4. The letter “e” is used to represent ________________________________________________
An upper case, or capital, letter is used to represent a dominant trait. A lower case, or small, letter is used to represent a recessive trait. Dominant traits completely mask and/or suppress recessive traits.

5. List nine dominant traits shown in the key.
________________________
________________________
________________________
________________________
________________________
________________________
________________________
________________________
________________________

6. List nine recessive traits shown in the key.

________________________
________________________
________________________
________________________
________________________
________________________
________________________
________________________
________________________

The simplest form of genetic inheritance for a single trait involves receiving one piece of genetic information (one allele) from the mother and one piece of genetic information (one allele) from the father. Sometimes the information from the mom and dad is identical, and sometimes it is not. The resulting combination of alleles is referred to as a genotype; while the physical expression of the trait that is coded for is referred to as a phenotype. For example, the genotype for our long necked dragon could be either NN or Nn; the phenotype for this trait would be a long neck.

INSTRUCTIONS: Using the “Dragon Genetics Key” as a reference, fill in the missing symbols for alleles (genotypes) or descriptions of physical appearance (phenotypes) in the table below. The first two rows are done for you. Remember, dominant traits appear when either one or two copies of the dominant allele are present. For example, “NN” and “Nn” both cause the dragon’s neck to be long. Only in the case of “nn” would the dragon’s neck be short because no dominant allele for a long neck is present.

Trait (Characteristic)
Symbols for Alleles
Appearance
Neck size
NN or Nn
Long neck
Neck size
nn
Short neck
Number of claws
cc

Spikes on tail?

No spikes
Eye color
EE

Horns? (present or absent)
hh

Fire breathing?
______ or ______
Breathes fire
Wing size
WW or Ww

Ear frills?

Has ear frills
Body covering
______ or ______
Scales

A trait that is codominant is one that is able to “mix” together, so that both traits are expressed in the phenotype. This creates a third, or sometimes more, alternatives of the characteristic; rather than only two forms of gene expression.

7. What phenotype would a dragon exhibit if it inherited an “Ll” genotype? ________________
______________________________________________________________________________
8. What color dragon would result from the codominant traits “BG” ? _____________________
9. How about “RB” ? _____________________ 10. “RG” ? _____________________
Name _____________________________________ Period _______ Date _______________

Name _____________________________________ Period _______ Date _______________