Download genetics - El Camino College

Name_____________________
Complete Dominance
Incomplete Dominance
Monohybrid Cross: Ww x Ww
(Ww=widows peak; ww=no peak)
Sickle Cell Anemia Trait Cross: Ss x Ss
(SS = no sickle cell; Ss = sickle trait;
ss = sickle cell disease)
Genotypic Ratio:
Genotypic Ratio:
Phenotypic Ratio:
Phenotypic Ratio:
Complete Dominance
Incomplete Dominance
PTC Taster Cross: TT x tt
(TT or Tt = taster; tt = nontaster
Familial Hypercholesterolemia
Cross: Ff x ff (ff = normal cholesterol;
Ff = high chol.; FF = very high chol.)
Genotypic Ratio:
Genotypic Ratio:
Phenotypic Ratio:
Phenotypic Ratio:
2
Physiology 31 - Inheritance Simulation Lab
Students form groups of two and follow the handout instructions to see how several monogenetic
traits are inherited via meiosis and the recombination of chromosomes during fertilization.
Materials (per groups of 2 students each)
- 18 blue popsickle sticks or wooden tongue depressors
- 18 pink popsickle sticks or wooden tongue depressors
- One inch wide masking tape
- Dark colored marking pen (such as a Sharpie)
- 2 Handouts on genotypes and phenotypes
Directions
1. Form groups of two.
2. One person will pick up 18 blue sticks and the other will pick up 18 pink sticks from the box.
3. Tape your same color sticks together in pairs, so that you each have 9 pairs of sticks
(homologous chromosomes).
4. Determine whether you are homozygous recessive or heterozygous (if you have a dominant
phenotype, we’re going to assume you’re heterozygous) for each of the nine traits on the
genetic traits handout, and record your genotype and your partner’s on the handout.
5. If you are homozygous recessive for a trait, print one lower case letter that represents that
allele on each side of the TAPE on one pair of sticks. (Please do NOT write directly on the
sticks.)
6. If you are heterozygous for the trait, print one lower case letter on the tape on one side of the
pair of sticks, and the corresponding capital letter on the other side of the sticks.
7. Do steps 4-6 for all 9 genetic traits, using one pair of sticks for each trait.
8. Once both you and your lab partner have completed labeling your “homologous
chromosomes,” you will both toss your sticks onto the table top. This step represents the
independent assortment of homologous chromosomes during meiosis.
9. After the “chromosomes” land, pair up the letters (alleles) on the blue and pink sticks. This
step represents the recombination of homologous chromosomes during fertilization.
10. Record the genotypes and phenotypes of your first offspring on the handout.
11. Repeat steps 8-10 for a second offspring.
12. Compare the genotypes and phenotypes of your two “offspring.” Did they both have the
same or different traits?
13. When you finish, remove the tape from the sticks and return them to the box.
3
Trait
Genotype
Earlobes
Dominant
Phenotype
Free
Recessive
Phenotype
Attached
Genotype
Hairline
Widow’s peak
WW or Ww
ww
RR or Rr
No widow’s
peak
Unable to roll
Tongue
Able to roll
Hitchhiker’s
thumb
Little Finger
No 60° bend
HH or Hh
Bends 60°
hh
Bent
BB or Bb
Straight
bb
Hairy
Mid-digits
Interlaced
fingers
PTC
taster/nontaster
Gender
Hairy
MM or Mm
Hairless
mm
Left thumb over
right
Tastes bad
CC or Cc
cc
TT or Tt
Right thumb
over left
Tasteless
Female
XX
Male
XY
EE or Ee
ee
rr
tt
Phenotypic
Ratio in Class
4
Genotypes and Phenotypes from inheritance simulation.
First Offspring
Trait
Earlobes
Hairline
Tongue
Hitchhiker’s
thumb
Little Finger
Hairy
Mid-digits
Interlaced
Fingers
PTC
Gender
Your Genotype
Your Partner’s
Genotype
Genotype
Second Offspring
Phenotype
Genotype
Phenotype