Name______Date______Period_____

The Science of Inheritance

Marshan Genetics

The appearance on an organism-the phenotype-is the result of the combination of dominant and recessive alleles that make up its genotype. In this activity, you will randomly select the genotype of an organism and construct a phenotype. The fictitious organism you create will be called a Marshan. Marshans are simple organism with seven pairs of chromosomes and one gene per chromosome.

Key to Marshan Phenotypes and Genotypes

Phenotype

/

Genotype

Short neck / nn
Three eyes / ee
Long tail / tt
Red Legs / bb
Blue nose / rr
Three green humps / hh
Two body segments / ss

Phenotype

/

Genotype

Long neck / NN or Nn
Two eyes / EE or Ee
Short tail / TT or Tt
Blue Legs / BB or Bb
Red nose / RR or Rr
One green hump / HH or Hh
Three body segments / SS or Ss

Materials

Large Marshmellows (body Segments and Head)Toothpicks (neck)

Mini Marsh mellows (nose and humps) 7 brown paper bags

Pipe Cleaners (tail)paper-strip chromosomes

Thumbtacks (eye)4 markers(1 blue, 1 red, 1 green, 1 yellow)

Pushpins(leg)

PROCEDURE

  1. Have one person from your group take two chromosomes from each of the seven bags.
  2. Arrange the chromosomes in seven matching pairs.
  3. Use the chromosomes you selected to fill in the Data Table with the genotype and phenotype of your Marshan.

Trait / Genotype / Homozygous or Heterozygous / Phenotype / Dominant or Recessive
Neck Length
Eye number
Tail length
Leg color
Nose color
Hump number
Body segment
  1. With the materials provided, use your Marshan’s genotype and the phenotype key to construct a Marshan.
ANALYZE AND CONCLUDE
  1. Which of the Marshan phenotypes are recessive? How do you know these phenotypes are recessive?
  1. Can you infer the genotype of a Marshan based only on its phenotype? Explain.
  1. Compare your group’s Marshan to the Marshan of another group. What evidence do you see to support Mendel’s principle of independent assortment?

PUNNET SQUARE PROBLEMS

  1. Cross a heterozygous Long necked Marshan with a short necked Marshan. What percentage will be long necked? Short necked? What is the genotype ratio? What is the phenotype ratio?
  1. Cross a homozygous dominant blue legged Marshan with a red legged Marshan. What percentage of the children will be heterozygous? What is the genotype ratio? What is the phenotype ratio?
  1. Cross a blue nosed Marshan with a heterozygous red nosed Marshan? What percentage of the children will be blue nosed? What is the genotype ratio? What is the phenotype ratio?