NameDatePeriod

HBiology

Genetics Family Tree Lab

Purpose: To observe segregation during gamete formation; to create an alien family tree

Procedure:

  1. You will be given the genotypes of two “alien” parents. Each parent is heterozygous for all of the following traits. In addition to the eight traits listed below, the female alien is XX and the male alien is XY for the sex chromosomes.

Trait / Dominant Phenotype (Allele) / Recessive Phenotype (Allele)
Number of eyes / 3 eyes (E) / 1 eye (e)
Number of legs / Four (L) / Three (l)
Fur color / Blue (B) / Red (b)
Type of horns / 3 horns present (H) / 1 horn present (h)
Shape of teeth / Pointed teeth/fangs (F) / Straight teeth/no fangs (f)
Shape of eyes / Triangular (S) / Square (s)
Tail / Present (T) / Absent (t)
Eye color / Green (G) / Purple (g)
  1. On your family tree (attached), please draw the phenotypes of the two parent aliens. Create a fun name for your alien family in the space provided.
  2. Using the wooden “chromosomes” provided, you will determine the genotype of one baby alien resulting from the combination of two parental gametes. Each chromosome contains letters representing the alleles for the traits listed above. Female alleles are in pink, male alleles in blue. Remember that each parent is heterozygous for each of the above traits.
  3. Place the chromosomes in the bag provided. Shake the bag and dump out the contents. The alleles shown on the desktop will be the resulting genome of the baby alien. Match up homologous chromosomes and record these genotypes for each trait in the data table provided. Remember that the baby alien will receive one allele from each parent for each of the eight traits.
  4. Repeat step 4 for two more baby aliens.
  5. Draw a picture of all three baby aliens in the space provided in the family tree.

Data Table:

Trait / Genotype for:
Alien Baby #1 / Alien Baby #2 / Alien Baby #3
Number of eyes
Number of legs
Fur color
Type of horns
Shape of teeth
Shape of eyes
Tail
Eye Color
Sex (Male or Female)

Analysis Questions: (You may answer on a separate sheet of paper if you need more room.)

  1. How many alleles does each parent have for each trait? Where did each allele come from?
  1. How many alleles for a particular trait can one parent alien give to his or her baby alien? Why
  1. Why do the chromosomes have only one letter for each trait found on opposite sides of the stick? In other words, why can’t you get two PINK “E”s from one shuffle in the bag?
  1. Do all three alien children look the same? Explain why or why not.
  1. Think about the diversity exhibited in this alien family with only 8 traits. Remembering that the human genome has over 30,000 genes, can you offer an explanation why children often resemble their parents and siblings, but are very rarely, if ever, identical to them?
  1. Suppose one alien baby received both recessive alleles for fur color from his parents. He mated with another alien who was heterozygous for the trait. What are the chances that one of their children would be heterozygous for fur color? Show parental cross and Punnett square.
  1. If a homozygous dominant four-legged alien mated with another four-legged alien who was a carrier of the recessive trait, what are the chances that they would produce an offspring with three legs? Show parental cross and Punnett square.
  1. A male alien with fangs and triangular eyes mates with a female alien with perfectly straight teeth and perfectly square eyes. They have a baby alien who has square eyes and fangs. Can you determine the genotypes of the alien parents? If not, explain why. Be sure to include Punnett squares where needed.