Download Generation 1

Bird Genetics – Phenotype vs. Genotype and Competitive foraging
Students will work in pairs and produce two eggs, which will (hopefully) mature to
produce healthy and eventually reproductive young birds. Each student will be a
surrogate bird parent. The rare long-billed crested flycatcher. Surrogate parents need not
actually be of opposite sexes, but one must play the role of mother (double X
chromosome) and the other must play the role of father (XY chromosome). The
chromosomes will be separated according to Mendel’s law of independent assortment.
The genetic codes that are passed on to the babies will be recorded on the following
pages. The surrogate parents must then decode the genes (genotype) inherited by their
offspring to determine the phenotype traits of their baby.
Biology of the long-billed crested flycatcher
This rare species is found in the high desert of southeast Idaho. Plumage may be either
blue or black. Males are typically slightly larger then females. Both sexes will produce a
yellow crest on their heads. Males that have a crest are able to attract a mate, while males
without a crest are unable to attract a mate. Females with and without crests are able to
mate.
Although this species will feed on nuts and seeds, they appear to prefer Teddy Grahams,
which can be found in abundance in SE Idaho. This species will cache its food
cooperatively in underground bins (simulated here with coffee cans). Unfortunately, this
species may cache them awfully deep. Individuals with short beaks, a recessive trait, are
sometimes unable to reach to the bottom of the cache, and often die of starvation. Nature
can be brutal!
Procedure
1. Choose a partner carefully. The lab must be completed on time.
2. Each partner must pick up four 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
allele that is passed on to the baby.
4. The alleles from each pair of homologous chromosomes will be recorded in the data
sheet.
5. The decoding chart below indicates the phenotypic effect of each gene. The trait
produced by each pair of alleles should be recorded in Generation One on the data chart.
Remember that a CAPITAL letter is dominant over a small letter [recessive]. Each
group will produce two offspring! You must do steps 3-5 twice! You will get two
different results for two different offspring. Each individual should record their results
in Generation One.
6. Once your offspring are produced, each parent will then take on the role of one child.
Take a piece of paper and write your phenotype and corresponding genotype in large
letters so the rest of the class can see, and tape it to the front of your shirt. Come to the
front of the room so I can record your genotype on the graph.
7. Now it’s time to see how brutal nature can actually be. Your food has been
cooperatively cached in three separate caches (simulated here with coffee cans). In order
to pack on enough fat to survive migration, each bird must obtain (using only your beak!)
at least 20 teddy grahams and return them to your nest site (simulated here with your
paper cup). You have 5 minutes to complete this task. We will do this as a class and I
will time you all, to ensure fairness. If you do not have enough food, you die. You are
out of the competition. If you survive, you get a chance at reproduction. You may not
steal from other people’s nest sites. You may only take food from the cache.
8. If you have the appropriate phenotype, you now have a chance to breed and produce
another clutch (2 eggs). You have 30 seconds to find a mate. If you do not find a mate in
that time, or all the potential mates are taken, you are unable to reproduce, and
(effectively) die because you cannot pass your genes onto the next generation.
9. Those that are still in the competition get to repeat steps 2-8. This time, you will
record your results in Generation Two. Upon completion, we will examine the genotypic
and phenotypic composition of the population.
Questions
1. What was the phenotype of your offspring? How does genotype affect phenotype
over time?
2. How did the phenotype of the population change from the first generation to the
second generation?
3. How successful were your offspring? Were they able to compete in foraging? Were
they able to reproduce the following spring?
4. If we did this for many generations, what might we expect our population to look like
(phenotype) and be composed of genetically (genotype)?
Decoding of genes
Chromosome
Dominant Gene
Recessive Gene
Blue autosome
A. Long bill
a. short bill
Red autosome
B. Yellow crest
b. no crest
Green autosome
C. Blue body feathers
c. black body feathers
X chromosome
XX – female
Y chromosome
XY – male
Generation 1
Genotypes
Alleles in
Autosome color
Mother
Father
Blue
Aa
Aa
Red
Bb
Bb
Green
Cc
Cc
Sex
XX
XY
Egg Sperm
TRAIT - Phenotype of baby
Generation 2
Genotypes
Autosome color
Blue
Red
Green
Sex
Mother
Alleles in
Father
Egg Sperm
TRAIT - Phenotype of baby
Monitoring Phenotype and Genotype over Generations
Generation 1 Generation 2 Phenotype
Total # of individuals
AA
Long bill
Aa
Long bill
aa
Short bill
BB
Yellow crest
Bb
Yellow crest
bb
No crest
CC
Blue body feathers
Cc
cc
Blue body feathers
Black body
feathers
XX
Females
XY
Males