Names:

Dragon Genetics Lab

Dr. Pamela Esprivalo Harrell, University of North Texas, developed an earlier version of "Dragon Genetics" which is described in the January 1997 issue of Science Scope, 20:4, 33-37. Copyright 2005, Bob Farber, Central High School, Philadelphia, PA

Background

Students will work in pairs in the lab to produce a dragon from the random mixing of genetic traits. Each student will be a surrogate dragon parent. They will pick up a complete set of dragon chromosomes. One parent must pick up the XX chromosomes while the other parent must pick up the XY chromosomes. The homologous chromosomes will be separated according to Mendel’s law of Independent Assortment. The genetic codes that are passed on to the baby will be recorded on the following pages. The surrogate parents must then decode the genes inherited by their bundle of joy to determine the phenotype traits of their baby. Using the pictures at the end of the handout as examples of the traits, the parents will draw a picture of their baby dragon.

Procedure

  1. Choose a partner carefully. You and your partner will share the grade for this lab.The lab must be completed on time.
  2. Each partner must pick up five Popsicle sticks -- one of each color of autosome, and one sex chromosome stick. Each side of a stick represents a chromosome, and the two sides together represent a pair of homologous chromosomes.
  3. For each color autosome and then for the sex chromosomes, each parent will randomly drop his or her stick on the table. The side of the stick that is up represents the chromosome that is passed on to the baby.
  4. The alleles from each pair of homologous chromosomes will be recorded in the data chart on pages 3-4.
  5. The decoding chart on page 2 indicates the phenotypic effect of each gene. The trait produced by each pair of alleles should be recorded in the data chart. Remember that a CAPITAL letter is dominant over a small letter [recessive] unless the decoding chart indicates those traits are codominant, incompletely dominant, sex-influenced, or sex-limited.
  6. You will make a drawing of your baby dragon. Use the examples provided or your own artwork (as long as it is neat and shows the required traits).

DECODING OF THE GENES

Green Autosome
Dominant genes Recessive genes
A. no chin spike a. chin spike
B. nose spike b. no nose spike
C. three head flaps c. four head flaps
D. no visible ear hole d. visible ear hole
E. Long horns e. short horns

Red Autosome
Dominant genes Recessive genes
F. long neck f. short neck
G. [see below] g. [see below]
H. no back spikes h. back spikes
I. long tail i. short tail
J. horn tail j. no horn tail

Purple Autosome
Dominant genes Recessive genes
K. [see below] k. [see below]
L. no back hump l. back hump
M. [see below] m. [see below]
N. yellow eyes n. red eyes
O. large scales o. small scales

 
Yellow Autosome
Dominant genes Recessive genes
P. no spots on thigh p. spots on thigh
Q. flat feet q. arched feet
R small comb on head [see below] r. large comb on head
S. [See below] s. [See below]
T. [See below] t. [See below]

Sex Chromosome X
Dominant genes Recessive genes
U. regular thigh u. pointed thigh
V. four toes v. three toes
W. elbow spike w. no elbow spike
X. cat eyes vertical pupil x. round pupil
Z. Fangs z. no fangs
+ fire breather - non fire breather

Sex Chromosome Y
Dominant genes Recessive genes
U. regular thigh u. pointed thigh
V. four toes v. three toes
Y. male sex

Codominant Traits
KN spots on neck KB spots on back k. no spots

Incomplete Dominance
SS blue spots Ss purple spots ss red spots
MM eye pointed at each end Mm eye pointed at front only mm round eye

Sex-influenced traits
G. no wings g. wings [dominant in presence of male hormone]
T. no chest plate t. chest plate [dominant in presence of male hormone]

Sex-limited traits:
R or r : Only males have comb on head

Polygenic Inheritance-Genes: K, N, S, and P
Number of dominant alleles 0 1 2 3 4 5 6 7 8
Skin Color Albino Red Orange Yellow Green Blue Indigo Violet Black


Our Baby!

Green Autosomes
Genotypes Alleles in Phenotypic traits of baby
  Mom Dad Egg Sperm  
a          
b          
c          
d          
e          

Red Autosomes
Genotypes Alleles in Phenotypic traits of baby
  Mom Dad Egg Sperm  
f          
g          
h          
i          
j          

Purple Autosomes
Genotypes Alleles in Phenotypic traits of baby
  Mom Dad Egg Sperm  
k          
l          
m          
n          
o          

Yellow Autosomes
Genotypes Alleles in Phenotypic traits of baby
  Mom Dad Egg Sperm  
p          
q          
r          
s          
t          

Sex Chromosomes
Genotypes Alleles in Phenotypic traits of baby
  Mom Dad Egg Sperm  
u          
v          
w          
xy          
z          
+-          

Questions

  1. How does dropping the stick on the table and transcribing the letters on the sides facing up follow Mendel’s Law of Segregation? [First state the law.]
  2. Explain how dropping the green, orange, and red sticks illustrates Mendel’s Law of Independent Assortment? [First state the law.]
  3. The gene for red eyes is recessive, yet most of the dragons have red eyes. How can this happen? [Hint. The gene that causes dwarfism (achondroplasia) in humans is dominant.]
  4. What is the sex of your baby, HOW do you know?
  5. What traits are sex-linked? [First define “sex-linked”.]
  6. What traits are more likely to be found in males? [Consider sex-linked, sex-influenced and sex-limited traits.]
  7. How might these be an advantage to this sex? [Be creative in your answers.]
  8. What traits are more likely to be found in females?
  9. How might these be an advantage to this sex?
  10. Pick two traits that the sire and dame dragons are both heterozygous for. Do a dihybird cross with those two traits and list all possible phenotypes and percents.