Name_____________________________ Period______ Alleles and Dominance Independent Practice: Dragon Worksheet A Introduction Alleles represent one of the forms of the gene. Geneticists use letters to represent different alleles and different forms of the alleles. For example, the letter “n” can be used to symbolize the allele that codes for the length of the dragon’s neck. Upper case (the big letter) represents dominance; the lower case represents the recessive allele for the trait. 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. 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. The only letter combination that would represent a short-necked dragon would be “nn” (homozygous recessive). This would mean both the mom and the dad contributed one recessive, short neck allele (n) during the fertilization process. Using the key provided, answer the questions in the worksheet regarding dominant and recessive alleles.
Use this key to answer questions on the next page
Dragon Key Upper case letter represent dominant alleles; lowercase letters represent recessive alleles N = LONG NECK n = short neck
E = RED EYE e = white eye
H = HORN PRESENT h = horn absent
F = FIRE BREATHING f = not fire breathing
G = GREEN BODY g = grey body
L = LONG TAIL l = short tail
S = SPIKES ON END OF TAIL s = no spikes on end of tail
R = RED WINGS r = yellow wings
T = THREE TOES t = four toes
W = YELLOW BELLY w = white belly
B = BLACK TAIL SPIKES b = red tail spikes
K = Freckles k = No freckles
X = X chromosome / no ear frills (XX = female)
Y = Y chromosome / ear frills present(XY = male)
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 ____________________________________________
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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. Refer to the key, and answer the following questions. (traits are phenotypes- NOT LETTERS) 4. List five dominant traits shown in the key. _________________________________________________ _______________________________________________________________________________________________ ___________________________________________________________________________ 5. List five recessive traits shown in the key. _______________________________________________________________________________________________ ___________________________________________________________________________ INSTRUCTIONS Using the key from the last page, fill in the missing symbols for the allele (genotypes), the genotype (homozygous dominant, heterozygous, or homozygous recessive) and/or descriptions of physical appearance (phenotypes) in the table below. 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 (no dominant allele present!) Name of Genotype Trait Genotype Phenotype NN Neck size (or)
Homozygous dominant
Long neck
Nn Homozygous recessive
Spikes on tail Eye color
EE
Horn
hh
Fire breathing?
No spikes
Breathes fire (or)
Belly color
Ww
Heterozygous
Color of spikes
Red
Tail length
LL
Gender
XY
Long Neither
When finished, pick out at least 3 dominant genotypes and at least 3 recessive genotypes. Write them down in the space below. Then draw and color the dragon with its phenotype on the back. Ex) Neck size: NN (long neck), horn: hh (horn absent)
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